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Research Article| Volume 116, P319-327, March 2022

Hypothyroidism does not lead to worse prognosis in COVID-19: findings from the Brazilian COVID-19 registry

Open AccessPublished:January 18, 2022DOI:https://doi.org/10.1016/j.ijid.2022.01.016

      Highlights

      • This study analyzed 526 patients with COVID-19 with hypothyroidism and 526 controls.
      • Patients with hypothyroidism required less intensive care interventions.
      • Patients with hypothyroidism showed a trend of lower in-hospital mortality.
      • Hypothyroidism does not seem to be associated with a worse prognosis in COVID-19.

      Abstract

      Background

      It is not clear whether previous thyroid diseases influence the course and outcomes of COVID-19.

      Methods

      The study is a part of a multicentric cohort of patients with confirmed COVID-19 diagnosis from 37 hospitals. Matching for age, sex, number of comorbidities, and hospital was performed for the paired analysis.

      Results

      Of 7,762 patients with COVID-19, 526 had previously diagnosed hypothyroidism and 526 were matched controls. The median age was 70 years, and 68.3% were females. The prevalence of comorbidities was similar, except for coronary and chronic kidney diseases that were higher in the hypothyroidism group (p=0.015 and p=0.001). D-dimer levels were lower in patients with hypothyroid (p=0.037). In-hospital management was similar, but hospital length-of-stay (p=0.029) and mechanical ventilation requirement (p=0.006) were lower for patients with hypothyroidism. There was a trend of lower in-hospital mortality in patients with hypothyroidism (22.1% vs 27.0%; p=0.062).

      Conclusion

      Patients with hypothyroidism had a lower requirement of mechanical ventilation and showed a trend of lower in-hospital mortality. Therefore, hypothyroidism does not seem to be associated with a worse prognosis.

      Keywords

      List of Abbreviations

      COVID-19
      Coronavirus disease 19
      NTIS
      Non-thyroidal illness syndrome
      T3
      Triiodothyronine
      T4
      Thyroxine
      TSH
      Thyroid-stimulating hormone
      ICU
      Intensive Care Unit
      REDCap
      Research Data Capture
      COPD
      Chronic obstructive pulmonary disease
      SF ratio
      Peripheral oxygen saturation/fraction of inspired oxygen ratio
      GCS
      Glasgow coma score
      HR
      Heart rate
      RR
      Respiratory rate
      Sat O2
      Peripheral capillary oxygen saturation
      aPTT
      Activated partial thromboplastin time
      AST
      Aspartate transaminase
      ALT
      Alanine aminotransferase
      BNP
      B-type natriuretic peptide
      CPK
      Creatine phosphokinase
      NT-proBNP
      N-terminal pro-brain natriuretic peptide
      INR
      International normalized ratio
      VTE
      Venous thromboembolism
      ACE 2
      Angiotensin-converting enzyme 2

      Background

      A global health crisis was established with the emergence of COVID-19 (
      • Gelfand MJ
      • Jackson JC
      • Pan X
      • Nau D
      • Pieper D
      • Denison E
      • et al.
      The relationship between cultural tightness-looseness and COVID-19 cases and deaths: a global analysis.
      ). It is well known that individuals with some underlying medical conditions, such as cardiovascular diseases, cancer, obesity, diabetes, and hypertension, are more likely to develop severe COVID-19, require hospitalization and intensive care, and have higher mortality rates (
      • Marcolino MS
      • Pires MC
      • Ramos LEF
      • Silva RT
      • Oliveira LM
      • Carvalho RLR
      • et al.
      ABC2-SPH risk score for in-hospital mortality in COVID-19 patients: development, external validation and comparison with other available scores.
      ,
      • Sanyaolu A
      • Okorie C
      • Marinkovic A
      • Patidar R
      • Younis K
      • Desai P
      • et al.
      Comorbidity and its Impact on Patients with COVID-19.
      , ). Nevertheless, other conditions such as asthma and Chagas disease surprisingly have not been related to more severe cases of COVID-19 (
      • Soeroto AY
      • Purwiga A
      • Emmy H
      • Pranggono EHP
      • Roesli RMA.
      Asthma does not increase COVID-19 mortality and poor outcomes: A systematic review and meta-analysis.
      ). However, many factors that interfere with COVID-19 clinical characteristics, symptoms, and prognosis are still unknown and require further investigation to improve disease prevention and patient management.
      It is not clear whether a previous thyroid disease influences COVID-19 course (
      • Duntas LH
      • Jonklaas J.
      COVID-19 and Thyroid Diseases: A Bidirectional Impact.
      ). Previous studies suggested that patients’ thyroid status might have a direct impact on the course of COVID-19 owing to the effects of thyroid hormone on multiple organs systems, including the cardiovascular and respiratory systems (
      • Duntas LH
      • Jonklaas J.
      COVID-19 and Thyroid Diseases: A Bidirectional Impact.
      ). Some studies have indeed observed that hypothyroidism may be associated with an increased risk for COVID-19 or a poorer prognosis in patients with the disease (
      • Bakshi SS
      • Kalidoss VK.
      Is there an association between hypothyroidism and COVID 19?: A preliminary report.
      ,
      • Zhang Y
      • Lin F
      • Tu W
      • Zhang J
      • Choudhry AA
      • Ahmed O
      • et al.
      Thyroid dysfunction may be associated with poor outcomes in patients with COVID-19.
      ). However, these studies are limited due to small sample sizes and lack of comparison with patients without hypothyroidism.
      Other studies have found that previous diagnosis of hypothyroidism or other thyroid diseases were not a risk factor for COVID-19 infection and were not associated with poorer outcomes of the disease (
      • Daraei M
      • Hasibi M
      • Abdollahi H
      • Mirabdolhagh Hazaveh M
      • Zebaradst J
      • Hajinoori M
      • et al.
      Possible role of hypothyroidism in the prognosis of COVID-19.
      ,
      • van Gerwen M
      • Alsen M
      • Little C
      • Barlow J
      • Naymagon L
      • Tremblay D
      • et al.
      Outcomes of Patients With Hypothyroidism and COVID-19: A Retrospective Cohort Study.
      ,
      • Martins JRM
      • Villagelin DGP
      • Carvalho GA
      • Vaisman F
      • Teixeira PFS
      • Scheffel RS
      • et al.
      Management of thyroid disorders during the COVID-19 outbreak: a position statement from the Thyroid Department of the Brazilian Society of Endocrinology and Metabolism (SBEM).
      ,
      • Shabrawishi M
      • Al-Gethamy MM
      • Naser AY
      • Ghazawi MA
      • Alsharif GF
      • Obaid EF
      • et al.
      Clinical, radiological and therapeutic characteristics of patients with COVID-19 in Saudi Arabia.
      ). It is well known that critically ill patients with no previous history of thyroid dysfunction usually present alterations in thyroid hormone levels, a situation known as nonthyroidal illness syndrome (NTIS) (
      • Fliers E
      • Bianco AC
      • Langouche L
      • Boelen A.
      Thyroid function in critically ill patients.
      ). Patients with NTIS typically present with decreased concentrations of plasma triiodothyronine (T3), and low thyroxine (T4) levels, and usually slightly decreased concentrations of thyroid–stimulating hormone (TSH), which may be variable depending on the phase of the disease (
      • Fliers E
      • Bianco AC
      • Langouche L
      • Boelen A.
      Thyroid function in critically ill patients.
      ). In patients at the intensive care unit, with conditions such as sepsis, major trauma, burn, or cardiac surgery, NTIS has been associated with disease severity and mortality, without cause-effect association. Rather, NTIS is more likely to be seen as an adaptive mechanism to critical illnesses (
      • Fliers E
      • Bianco AC
      • Langouche L
      • Boelen A.
      Thyroid function in critically ill patients.
      ,
      • Kim SY
      • Yoo DM
      • Min CY
      • Choi HG.
      The Effects of Previous Thyroid Disease on the Susceptibility to, Morbidity of, and Mortality Due to COVID-19: A Nationwide Cohort Study in South Korea.
      ,
      • Martins JRM
      • Villagelin DGP
      • Carvalho GA
      • Vaisman F
      • Teixeira PFS
      • Scheffel RS
      • et al.
      Management of thyroid disorders during the COVID-19 outbreak: a position statement from the Thyroid Department of the Brazilian Society of Endocrinology and Metabolism (SBEM).
      ). As we could expect, NTIS has been frequently observed in patients with COVID-19 with the same pattern as in other critical conditions (
      • Beltrão FEL
      • Beltrão DCA
      • Carvalhal G
      • Beltrão FEL
      • Brito AS
      • Capistrano KHR
      • et al.
      Thyroid Hormone Levels During Hospital Admission Inform Disease Severity and Mortality in COVID-19 Patients.
      ,
      • Gao W
      • Guo W
      • Guo Y
      • Shi M
      • Dong G
      • Wang G
      al.Thyroid hormone concentrations in severely or critically ill patients with COVID-19.
      ,
      British Columbia Ministry of Health
      Thyroid Function Testing in the Diagnosis and Monitoring of Thyroid Function Disorder.
      ).
      Literature regarding the association between COVID-19 and previous hypothyroidism is still controversial, results may be biased by the inclusion of patients with NTIS, and more studies with larger sample sizes and comparison with patients without hypothyroidism are still needed. This study aims to compare the evolution of COVID-19 in patients with previous diagnosis of underlying hypothyroidism to patients without the disease to understand if hypothyroidism is an independent risk factor in the course of COVID-19.

      Methods

      Study design and subjects

      This study is a part of the multicentric cohort study Brazilian COVID-19 Registry. Consecutive patients with confirmed COVID-19 by reverse transcriptase–polymerase chain reaction (RT-PCR) or serological tests (IgM) (
      • Marcolino MS
      • Ziegelmann PK
      • Souza-Silva MVR
      • Nascimento IJB
      • Oliveira LM
      • Monteiro LS
      • et al.
      Brazilian COVID-19 Registry Investigators. Clinical characteristics and outcomes of patients hospitalized with COVID-19 in Brazil: Results from the Brazilian COVID-19 registry.
      ,

      World Health Organization. Diagnostic testing for SARS-CoV-2. Interim guidance. Online. 11 September 2020. Available at: https://www.who.int/publications/i/item/diagnostic-testing-for-sars-cov-2.

      ) who were admitted to the 37 participant hospitals from March 1, 2020, to September 31, 2020, were eligible (
      • Marcolino MS
      • Ziegelmann PK
      • Souza-Silva MVR
      • Nascimento IJB
      • Oliveira LM
      • Monteiro LS
      • et al.
      Brazilian COVID-19 Registry Investigators. Clinical characteristics and outcomes of patients hospitalized with COVID-19 in Brazil: Results from the Brazilian COVID-19 registry.
      ). Patients were admitted from March 1, 2020, to September 31, 2020.
      For the current analysis, “cases” were patients with a clinical history of previously diagnosed hypothyroidism, who were on levothyroxine replacement therapy. Of 7,762 patients with confirmed COVID–19 diagnosis, 555 (7.15%) had underlying hypothyroidism. Of those, 21 were excluded due to hospital admission for other reasons (not COVID-19), 3 were excluded due to pregnancy, and 5 were transferred to other hospitals, with 526 patients with hypothyroidism remaining eligible for the study (Figure 1). Those patients were admitted in 31 hospitals, which were located in 15 cities (Belo Horizonte, Betim, Curvelo, Ipatinga, Teófilo Otoni, Divinópolis, Porto Alegre, Bento Gonçalves, Santa Cruz do Sul, Canoas, Santa Maria, Lajeado, Chapecó, Florianópolis, and Botucatu) in 4 Brazilian states (Minas Gerais, Rio Grande do Sul, Santa Catarina, and São Paulo). Of those, 13 were public hospitals, 15 private hospitals, and 3 mixed hospitals. To compare patient outcomes and disease course, a paired analysis was made with matched controls with no previous history of hypothyroidism.
      Fig 1
      Fig. 1Flowchart of patients included in the study.
      This study adheres to the Strengthening the Reporting of Observational Studies in Epidemiology guidelines (STROBE) (
      • von Elm E
      • Altman DG
      • Egger M
      • Pocock SJ
      • Gøtzsche PC
      • Vandenbroucke JP
      • et al.
      Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies.
      ), and it has been conducted by a protocol approved by the National Commission for Research Ethics (CAAE 30350820.5.1001.0008) (
      • Barreto PA
      • Braga AS
      • Andrade M.
      Evaluation of completeness of dengue records: exploratory study of compulsory notices.
      ). Individual informed consent was waived due to the pandemic and to the fact that all data collected were unidentified and gathered through medical records.

      Data collection

      Data were collected through the analysis of medical records by trained health professionals or undergraduate students (from medical and nursing schools) using Research Data Capture (REDCap) tools (
      • Harris PA
      • Taylor R
      • Minor BL
      • Elliott V
      • Fernandez M
      • O'Neal L
      • et al.
      The REDCap consortium: Building an international community of software platform partners.
      ). In the medical records, data collected concerned demographic and clinical characteristics, comorbidities, medication in use before admission, COVID-19 symptoms, clinical evaluation at admission, laboratory and radiological examinations, medication used during hospitalization, and outcomes. Study protocol and definitions were published elsewhere (
      • Marcolino MS
      • Ziegelmann PK
      • Souza-Silva MVR
      • Nascimento IJB
      • Oliveira LM
      • Monteiro LS
      • et al.
      Brazilian COVID-19 Registry Investigators. Clinical characteristics and outcomes of patients hospitalized with COVID-19 in Brazil: Results from the Brazilian COVID-19 registry.
      ).

      Statistical analysis

      Statistical analysis was performed using R software (version 4.0.2). To adjust for potential confounding variables, patients who had underlying hypothyroidism were matched with patients who did not have underlying hypothyroidism (controls) on the basis of propensity score. Propensity score model was estimated by logistic regression and included sex, age, number of comorbidities (hypertension, diabetes mellitus, obesity, coronary artery disease, heart failure, atrial fibrillation or flutter, cirrhosis, chronic obstructive pulmonary disease, cancer, and previous stroke) (
      • Marcolino MS
      • Ziegelmann PK
      • Souza-Silva MVR
      • Nascimento IJB
      • Oliveira LM
      • Monteiro LS
      • et al.
      Brazilian COVID-19 Registry Investigators. Clinical characteristics and outcomes of patients hospitalized with COVID-19 in Brazil: Results from the Brazilian COVID-19 registry.
      ), and hospital. Patients from the control group were searched to find those who had the closest propensity score from the hypothyroidism group (within 0.17 standard deviations of the logit of the propensity score on a scale from 0-1.00) using the MatchIt package in R software.
      Categorical data were presented as absolute frequency and proportions, and continuous variables were expressed as medians and interquartile ranges. The chi-square and Fisher's exact tests were used to compare the distribution of categorical variables and the Wilcoxon–Mann–Whitney test for continuous variables. Results were considered statistically significant if the two-tailed P-value was < 0.05.

      Results

      The study sample comprehended 526 individuals with previous hypothyroidism history and 526 matched controls. The median age was 70 years (59-80), and 68.3% were female. Most patients (85.8%) had at least 1 comorbidity, with the most common being hypertension (72.0%), diabetes mellitus (38.8%), obesity (18.9%), and heart failure (11.2%). In comparison to the controls, patients with underlying hypothyroidism had similar prevalence of comorbidities and unhealthy habits, except for a higher prevalence of coronary disease (9.7% vs 5.7%, p=0.015) and chronic kidney disease (9.9% vs 4.8%, p= 0.001) among the hypothyroidism group (Table 1). [insert Table 1]
      Table 1Demographics and clinical characteristics of the study cohort
      Hypothyroidism N = 526
      Median (IQR) or n (%)
      Control patients N = 526
      Median (IQR) or n (%)
      p-value
      Pearson's chi-square test; Wilcoxon rank sum test; Fisher's exact test. COPD - Chronic obstructive pulmonary disease
      Age (years)71.0 (60.0, 80.0)70.0 (59.0, 80.0)0.659
      Female sex356 (67.7%)363 (69.0%)0.643
      Cardiovascular diseases
      Hypertension370 (70.3%)387 (73.6%)0.243
      Heart failure65 (12.4%)53 (10.1%)0.241
      Coronary artery disease51 (9.7%)30 (5.7%)0.015
      Atrial fibrillation/flutter36 (6.8%)37 (7.0%)0.903
      Stroke28 (5.3%)34 (6.5%)0.432
      Respiratory diseases
      COPD42 (8.0%)44 (8.4%)0.822
      Asthma35 (6.7%)34 (6.5%)0.901
      Metabolic diseases
      Diabetes mellitus215 (40.9%)193 (36.7%)0.164
      Obesity (BMI > 30 kg/m2)94 (17.9%)95 (18.1%)0.936
      Other conditions
      Chronic kidney disease52 (9.9%)25 (4.8%)0.001
      Cancer29 (5.5%)38 (7.2%)0.256
      Dementia16 (3.0%)11 (2.1%)0.330
      Rheumatological disease16 (3.0%)9 (1.7%)0.157
      Cirrhosis4 (0.8%)7 (1.3%)0.363
      Transplant3 (0.6%)3 (0.6%)>0.999
      HIV infection2 (0.4%)4 (0.8%)0.687
      Comorbidities (total number)0.549
      071 (13.5%)78 (14.8%)
      1157 (29.8%)143 (27.2%)
      2163 (31.0%)173 (32.9%)
      387 (16.5%)95 (18.1%)
      436 (6.8%)31 (5.9%)
      >= 512 (2.3%)6 (1.2%)
      Toxic habits
      Alcoholism10 (1.9%)10 (1.9%)>0.999
      Smoking100 (19.0%)115 (21.9%)0.251
      1 Median (IQR) or n (%)
      2 Pearson's chi-square test; Wilcoxon rank sum test; Fisher's exact test.COPD - Chronic obstructive pulmonary disease
      The median duration of symptoms was 6 days (3-9 days) for both groups. The most predominant symptoms in disease presentation were dyspnea, fever, and dry cough, being similar in both groups. Upon hospital presentation, patients with hypothyroidism had a lower frequency of respiratory rate over 24 breaths per minute (36.1% vs 42.0%; p=0.050), as well as lower proportion of mechanical ventilation (4.0% vs 7.4%; p=0.016) and of inotropics (24.3% vs 29.8%; p=0.044) requirement. The median peripheral oxygen saturation/fraction of inspired oxygen ratio (SF ratio) was slightly higher in patients with hypothyroidism than in the control group (428.6 vs 423.8, p=0.034), as shown in Table 2. [insert Table 2]
      Table 2Clinical characteristics at hospital admission.
      HypothyroidismControl patients
      N = 526
      Median (IQR) or n (%)
      Non missing casesN = 526
      Median (IQR) or n (%)
      Non missing casesp-value
      Inotropic use at hospital presentation SF ratio: peripheral capillary oxygen saturation/fraction of inspired oxygen (Spo2/Fio2 ratio) GCS: Glasgow Coma Scale; HR: heart rate; RR: respiratory rate; Sat O2: peripheral capillary oxygen saturation
      Symptoms
      Duration of symptoms (days)6.0 (3.0, 9.0)5246.0 (3.0, 9.0)5240.635
      Adynamic138 (26.2%)526143 (27.2%)5260.728
      Ageusia25 (4.8%)52634 (6.5%)5260.228
      Anosmia44 (8.4%)52648 (9.1%)5260.662
      Headache95 (18.1%)52694 (17.9%)5260.936
      Rhinorrhea72 (13.7%)52679 (15.0%)5260.538
      Diarrhea84 (16.0%)52677 (14.6%)5260.549
      Dyspnea298 (56.7%)526316 (60.1%)5260.260
      Fever278 (52.9%)526247 (47.0%)5260.056
      Hyporexia71 (13.5%)52666 (12.5%)5260.647
      Neurological manifestations14 (2.7%)52621 (4.0%)5260.229
      Myalgia147 (27.9%)526130 (24.7%)5260.234
      Nausea/vomiting83 (15.8%)52669 (13.1%)5260.220
      Productive cough71 (13.5%)52679 (15.0%)5260.481
      Dry cough262 (49.8%)526268 (51.0%)5260.711
      Clinical assessment
      GCS < 1584 (16.0%)52683 (15.8%)5260.933
      HR (bpm)85.0 (74.0, 96.0)50587.0 (76.0, 98.0)5070.169
      HR > 100 bpm116 (22.1%)526131 (24.9%)5260.275
      RR (bpm)20.0 (18.0, 23.0)44320.0 (18.0, 24.0)4300.216
      RR > 24 bpm190 (36.1%)526221 (42.0%)5260.050
      Sat O2 (%)94.0 (91.0, 96.0)51394.0 (91.0, 97.0)5130.845
      Sat O2 < 90%98 (18.6%)526103 (19.6%)5260.695
      Mechanical ventilation21 (4.0%)52639 (7.4%)5240.016
      Systolic blood pressure5265260.693
      SBP >= 90 mmHg482 (91.6%)464 (88.2%)
      SBP < 90 mmHg25 (4.8%)28 (5.3%)
      Inotropic use
      Inotropic use at hospital presentation SF ratio: peripheral capillary oxygen saturation/fraction of inspired oxygen (Spo2/Fio2 ratio) GCS: Glasgow Coma Scale; HR: heart rate; RR: respiratory rate; Sat O2: peripheral capillary oxygen saturation
      19 (3.6%)34 (6.5%)
      SF ratio
      Inotropic use at hospital presentation SF ratio: peripheral capillary oxygen saturation/fraction of inspired oxygen (Spo2/Fio2 ratio) GCS: Glasgow Coma Scale; HR: heart rate; RR: respiratory rate; Sat O2: peripheral capillary oxygen saturation
      428.6 (339.3, 452.4)507423.8 (304.7, 452.4)5070.034
      1 Median (IQR) or n (%)
      2 Inotropic use at hospital presentationSF ratio: peripheral capillary oxygen saturation/fraction of inspired oxygen (Spo2/Fio2 ratio)GCS: Glasgow Coma Scale; HR: heart rate; RR: respiratory rate; Sat O2: peripheral capillary oxygen saturation
      Laboratory examinations and biomarkers were similar between groups, except for D-dimer, which was lower in patients with hypothyroidism than in the controls (Table 3). [insert Table 3]
      Table 3Findings of laboratory examinations.
      HypothyroidismControl patients
      N = 526
      Median (IQR) or n (%) 2Wilcoxon rank sum test; Fisher's exact test aPTT: activated partial thromboplastin time; AST: aspartate transaminase; ALT: alanine aminotransferase; BNP B-type natriuretic peptide; CPK: creatine phosphokinase; NT-proBNP: N-terminal pro-brain natriuretic peptide; INR: international normalized ratio * Times the reference value.
      Non missing casesN = 526
      Median (IQR) or n (%) 2Wilcoxon rank sum test; Fisher's exact test aPTT: activated partial thromboplastin time; AST: aspartate transaminase; ALT: alanine aminotransferase; BNP B-type natriuretic peptide; CPK: creatine phosphokinase; NT-proBNP: N-terminal pro-brain natriuretic peptide; INR: international normalized ratio * Times the reference value.
      Non missing casesp-value2
      Hemogram
      Hemoglobin (g/L)12.6 (11.6, 13.9)51512.9 (11.6, 13.8)5090.301
      Leukocytes count (cels/mm3)6,785.0 (5,000.0, 9,302.5)5126,940.5 (5,200.0, 9,132.5)5100.317
      Neutrophils (cels/mm3)4,737.0 (3,310.5, 7,155.8)4985,204.0 (3,481.8, 7,281.2)4880.205
      Lymphocytes (cels/mm3)1,100.0 (760.0, 1,503.5)4991,041.0 (710.0, 1,421.0)4890.136
      Platelet count (109/L)195.0 (151.0, 244.8)508196.3 (152.0, 261.0)5050.499
      aPTT (secs/control)1.0 (0.9, 1.2)2281.0 (0.9, 1.2)2650.396
      Liver panel
      Albumin (g/dL)3.4 (3.0, 3.7)903.3 (3.0, 3.6)1040.283
      Total bilirubin (mg/dL)0.4 (0.3, 0.6)2530.4 (0.3, 0.6)2490.150
      Direct bilirubin (mg/dL)0.2 (0.1, 0.3)2510.2 (0.1, 0.3)2490.013
      AST (U/L)37.4 (29.0, 55.0)32638.0 (28.0, 52.0)3340.750
      ALT (U/L)29.0 (20.0, 46.0)32328.0 (19.0, 44.3)3350.592
      Electrolytes
      Calcium (mmol/L)1.1 (1.1, 1.2)1381.1 (1.1, 1.2)1670.298
      Potassium (mmol/L)4.2 (3.8, 4.6)4764.1 (3.7, 4.5)4850.065
      Sodium (mmol/L)137.0 (134.0, 139.7)474137.7 (135.0, 140.0)4820.020
      Others
      BNP (pg/mL)78.0 (23.0, 230.5)47110.0 (32.8, 312.0)480.218
      Creatinine (mg/dL)0.9 (0.8, 1.4)4930.9 (0.7, 1.2)4990.159
      CPK (U/L)81.5 (45.2, 145.8)15074.5 (47.0, 189.9)1490.668
      D-dimer*2.3 (1.2, 6.8)3012.9 (1.2, 23.9)3180.037
      Ferritin (ng/mL)80.1 (57.7, 142.0)1966.0 (42.0, 175.3)170.447
      Fibrinogen (g/L)465.5 (334.5, 591.8)40451.0 (343.0, 553.0)450.745
      Lactate dehydrogenase358.5 (255.2, 493.8)282363.0 (270.0, 504.0)2970.536
      NT-proBNP (pg/mL)310.0 (114.0, 785.7)55302.0 (89.3, 1,197.5)700.895
      C-reactive protein (mg/L)75.3 (32.1, 134.3)46674.8 (34.3, 143.3)4410.933
      PTTa (secs/control)1.0 (0.9, 1.2)2281.0 (0.9, 1.2)2650.396
      INR1.1 (1.0, 1.2)2911.1 (1.0, 1.2)3170.229
      Troponin*0.3 (0.1, 0.5)1710.3 (0.1, 0.5)1840.261
      Lactate1.4 (1.0, 1.9)3111.4 (1.1, 1.9)3210.427
      Urea (mg/dL)39.1 (28.0, 58.0)49238.0 (28.0, 55.8)4840.539
      1 Median (IQR) or n (%) 2Wilcoxon rank sum test; Fisher's exact testaPTT: activated partial thromboplastin time; AST: aspartate transaminase; ALT: alanine aminotransferase; BNP B-type natriuretic peptide; CPK: creatine phosphokinase; NT-proBNP: N-terminal pro-brain natriuretic peptide; INR: international normalized ratio* Times the reference value.
      As for medications used during hospitalization, patients with hypothyroidism had a lower frequency of inotropes requirement than the control group (24.3% vs 29.8%, p=0.044). The other medications were similar between groups (Table S1).
      Regarding patient outcomes, the median hospital length of stay (8 versus 9 days; p=0.029) and mechanical ventilation requirement (25.4% versus 33.1%; p=0.006) were lower in patients with hypothyroidism than in controls. A trend of lower in-hospital mortality was seen in patients with hypothyroidism (22.1% versus 27.0%; p=0.062). The other outcomes were similar between groups, as shown in Table 4. [insert Table 4]
      Table 4Patient outcomes
      HypothyroidismN = 5261Control patientsN = 526
      Median (IQR) or n (%) 2Wilcoxon rank sum test; Pearson's chi-square test; Fisher's exact test ICU: intensive care unit; VTE: venous thromboembolism
      p-value2
      Hospital length of stay, days8.0 (4.0, 14.0)9.0 (5.0, 14.2)0.029
      ICU, days197 (37.5%)224 (42.6%)0.089
      Time of ICU admission1.0 (0.0, 3.0)1.0 (0.0, 2.0)0.089
      Days at ICU8.0 (3.0, 15.0)8.0 (4.0, 17.0)0.293
      Mechanical ventilation, number of patients133 (25.4%)172 (33.1%)0.006
      Dialysis57 (10.8%)63 (12.0%)0.553
      Sepsis72 (13.7%)90 (17.1%)0.124
      Disseminated intravascular coagulation0 (0.0%)3 (0.6%)0.249
      Decompensated chronic heart failure16 (3.0%)25 (4.8%)0.152
      Acute heart failure3 (0.6%)6 (1.1%)0.506
      Nosocomial infection48 (9.1%)48 (9.1%)>0.999
      Miocardites0 (0.0%)3 (0.6%)0.249
      Hemorrhage10 (1.9%)9 (1.7%)0.817
      Vascular thrombosis18 (3.4%)22 (4.1%)0.519
      VTE16 (3.0%)21 (4.0%)0.403
      Arterial thrombosis2 (0.4%)1 (0.2%)>0.999
      In hospital mortality116 (22.1%)142 (27.0%)0.062
      1 Median (IQR) or n (%) 2Wilcoxon rank sum test; Pearson's chi-square test; Fisher's exact testICU: intensive care unit; VTE: venous thromboembolism

      Discussion

      In this multicenter cohort of in-hospital patients with COVID-19, those who had hypothyroidism had similar comorbidities, clinical manifestations, and laboratory parameters to the control group. Surprisingly, requirement for mechanical ventilation was remarkably lower in patients with underlying hypothyroidism, and there was a trend for lower hospital mortality than controls matched for age, sex, number of comorbidities, and hospital.
      Underlying individual comorbidities were similar between groups, except for chronic kidney disease and coronary artery disease. There has been a great interest in the relationship between thyroid dysfunction and kidney function in recent years (
      • Iglesias P
      • Bajo MA
      • Selgas R
      • Díez JJ.
      Thyroid dysfunction and kidney disease: An update.
      ,
      • Narasaki Y
      • Sohn P
      • Rhee CM.
      The Interplay Between Thyroid Dysfunction and Kidney Disease.
      ). Thyroid hormones have shown to directly affect the kidneys, influencing renal growth and development, glomerular filtration rate, renal transport systems, and sodium and water homeostasis. An indirect effect through modifications in cardiac and vascular function and disruptions in the renin-angiotensin system is also believed to play an important role in reducing glomerular filtration rate through impaired renal autoregulation. At the same time, patients with autoimmune thyroid disorders are also at risk for immune-mediated glomerular diseases (
      • Narasaki Y
      • Sohn P
      • Rhee CM.
      The Interplay Between Thyroid Dysfunction and Kidney Disease.
      ).
      As for the higher prevalence of coronary artery disease, the association between hypothyroidism and increased cardiovascular risk is controversial when TSH is normal (
      • Decandia F.
      Risk factors for cardiovascular disease in subclinical hypothyroidism.
      ). Nonetheless, it was demonstrated that patients with underlying hypothyroidism with a poor disease control have a worse lipidic profile and a higher prevalence of atherosclerosis because thyroid hormones regulate lipid metabolism, especially TSH (
      • Delitala AP
      • Fanciulli G
      • Maioli M
      • Delitala G.
      Subclinical hypothyroidism, lipid metabolism and cardiovascular disease.
      ,
      • Kotwal A
      • Cortes T
      • Genere N
      • Hamidi O
      • Jasim S
      • Newman CB
      • et al.
      Treatment of Thyroid Dysfunction and Serum Lipids: A Systematic Review and Meta-analysis.
      ,
      • Tan M
      • Korkmaz H
      • Aydın H
      Kumbul Doğuç D. FABP4 levels in hypothyroidism and its relationship with subclinical atherosclerosis.
      ). At the same time, it is well established that a key factor for adverse cardiovascular events prevention in patients with hypothyroidism is the achievement of symptom control and levels of TSH and T4 within the reference values with the use of hormonal replacement therapy (
      • Sue LY
      • Leung AM.
      Levothyroxine for the Treatment of Subclinical Hypothyroidism and Cardiovascular Disease.
      ). Another hypothesis to explain the higher frequency of coronary artery disease is the higher prevalence of chronic kidney disease, which is associated with increased cardiovascular risk.
      There was no difference in frequency and severity of COVID-19 symptoms between groups, including anosmia and ageusia. Despite the previous evidence of an effect of hypothyroidism at gustatory and olfactory perceptual pathways, including receptors, central olfactory and gustatory areas, and high order cognitive systems, previous cohort studies did not observe a higher frequency of gustatory or olfactory COVID-19 symptoms in these patients. However, a case series has observed an independent association between hypothyroidism and a higher likelihood of persistent olfactory dysfunction among patients with COVID-19 (odds ratio [OR]: 21.1; 95% CI: 2.0–219.4) (
      • Tsivgoulis G
      • Fragkou PC
      • Karofylakis E
      • Paneta M
      • Papathanasiou K
      • Palaiodimou L
      • et al.
      Hypothyroidism is associated with prolonged COVID-19-induced anosmia: a case-control study.
      ). Further studies are needed to investigate whether hypothyroidism is indeed associated with a higher risk of persistent symptoms.
      Overall, laboratorial examinations were similar between groups, except for D-dimer levels, which were slightly higher in the control group than in patients with hypothyroidism. However, the values were assessed as the number of times above the upper limit of normal, and the difference is not clinically relevant. These findings are different from a study from Wuhan, China, in the early phase of the pandemic, which observed that patients with thyroid dysfunction had persistently high levels of biomarkers for inflammatory response and cardiac injury. However, authors defined thyroid dysfunction by abnormal thyroid function test results within 3 days from admission and not previous underlying diseases (
      • Zhang Y
      • Lin F
      • Tu W
      • Zhang J
      • Choudhry AA
      • Ahmed O
      • et al.
      Thyroid dysfunction may be associated with poor outcomes in patients with COVID-19.
      ).
      Current data show that COVID-19 is associated with a broad spectrum of thyroid dysfunction, ranging from thyrotoxicosis to NTIS and hypothyroidism, which may worsen disease course and affect prognosis (
      • Baldelli R
      • Nicastri E
      • Petrosillo N
      • Marchioni L
      • Gubbiotti A
      • Sperduti I
      • et al.
      Thyroid dysfunction in COVID-19 patients.
      ,
      • Malik J
      • Zaidi SMJ
      • Waqar AU
      • Khawaja H
      • Malik A
      • Ishaq U
      • et al.
      Association of hypothyroidism with acute COVID-19: a systematic review.
      ,
      • Ruggeri RM
      • Campennì A
      • Deandreis D
      • Siracusa M
      • Tozzoli R
      • Petranović Ovčariček P
      • et al.
      SARS-COV-2-related immune-inflammatory thyroid disorders: facts and perspectives.
      ,
      • Schwarz Y
      • Percik R
      • Oberman B
      • Yaffe D
      • Zimlichman E
      • Tirosh A.
      Sick Euthyroid Syndrome on Presentation of Patients With COVID-19: A Potential Marker for Disease Severity.
      ,
      • Zou R
      • Wu C
      • Zhang S
      • Wang G
      • Zhang Q
      • Yu B
      • et al.
      Euthyroid Sick Syndrome in Patients With COVID-19.
      ). This was observed even in mild to moderate COVID-19 cases, independently of SARS-CoV-2 viral load, age, and inflammation and tissue injury markers (
      • Lui DTW
      • Lee CH
      • Chow WS
      • Lee ACH
      • Tam AR
      • Fong CHY
      • et al.
      Role of non-thyroidal illness syndrome in predicting adverse outcomes in COVID-19 patients predominantly of mild-to-moderate severity.
      ). Cytokine storm and dysregulated inflammation are believed to affect the thyroid gland through the proinflammatory cytokines, which resembles the immune activation that occurs in immune-mediated thyroid diseases, causing damage and compromising function (
      • Ruggeri RM
      • Campennì A
      • Deandreis D
      • Siracusa M
      • Tozzoli R
      • Petranović Ovčariček P
      • et al.
      SARS-COV-2-related immune-inflammatory thyroid disorders: facts and perspectives.
      ). It is also possible that thyroid abnormalities are caused by a direct effect of the virus, leading to subacute thyroiditis, a self-limiting destructive thyroiditis, or an indirect effect on angiotensin-converting enzyme 2 (ACE2) receptors of thyroid follicular cells, leading to a thyroid malfunction (
      • Chakraborty U
      • Ghosh S
      • Chandra A
      • Ray AK.
      Subacute thyroiditis as a presenting manifestation of COVID-19: a report of an exceedingly rare clinical entity.
      ,
      • Ruggeri RM
      • Campennì A
      • Deandreis D
      • Siracusa M
      • Tozzoli R
      • Petranović Ovčariček P
      • et al.
      SARS-COV-2-related immune-inflammatory thyroid disorders: facts and perspectives.
      ). Other contributing factors may be the oxidative stress due to augmented reactive oxygen species generation, which are associated with NTIS, and changes in the intracellular redox state that may disrupt deiodinase function by independent mechanisms, which might include depletion of the—as yet unidentified—endogenous thiol cofactor (
      • Wajner SM
      • Maia AL.
      New Insights toward the Acute Non-Thyroidal Illness Syndrome.
      ). Nevertheless, there is no evidence that the administration of thyroid hormones improves prognosis in those patients. We might also wonder that in some studies that observed a correlation between thyroid dysfunction and more severe COVID-19 presentation, the alterations in thyroid hormone levels were actually due to NTIS, as opposed to an underlying previous clinical thyroid disease (
      • Bakshi SS
      • Kalidoss VK.
      Is there an association between hypothyroidism and COVID 19?: A preliminary report.
      ). Therefore, these results have to be carefully analyzed.
      Our findings suggest that underlying hypothyroidism does not lead to worse outcomes in patients with COVID-19. In fact, those patients presented indicators of better outcomes than patients without hypothyroidism. At hospital admission, respiratory rates over 24 breaths per minute were less frequent in patients with hypothyroidism than in the control group (36.1% vs 42.0%; p=0.050). It is known that tachypnea is one of the alarming COVID-19 symptoms as it may be an indicator of COVID-19 pneumonia (
      • Izquierdo JL
      • Ancochea J
      • Soriano JB.
      Clinical Characteristics and Prognostic Factors for Intensive Care Unit Admission of Patients With COVID-19: Retrospective Study Using Machine Learning and Natural Language Processing.
      ). Despite the fact that SF ratio, a strong predictor of COVID-19 prognosis and mortality (
      • Marcolino MS
      • Pires MC
      • Ramos LEF
      • Silva RT
      • Oliveira LM
      • Carvalho RLR
      • et al.
      ABC2-SPH risk score for in-hospital mortality in COVID-19 patients: development, external validation and comparison with other available scores.
      ,

      Mejía F, Medina C, Cornejo E, Morello E, Vásquez S, Alave J, et al. Oxygen saturation as a predictor of mortality in hospitalized adult patients with COVID-19 in a public hospital in Lima, Peru. PLoS One. 2020 Dec 28;15(12):e0244171. doi: 10.1371/journal.pone.0244171.

      ) , was slightly higher in patients with hypothyroidism, the difference was not clinically relevant (428.6 versus 423.8, p=0.034).
      The lower requirement of mechanical ventilation had not been observed previously, and it was quite unexpected. It is known that patients with decompensated hypothyroidism may have abnormalities in pulmonary function, muscle myopathy, and neuropathy with respiratory muscle weakness, but these abnormalities improve with treatment (
      • Laroche CM
      • Cairns T
      • Moxham J
      • Green M.
      Hypothyroidism presenting with respiratory muscle weakness.
      ,
      • Siafakas NM
      • Salesiotou V
      • Filaditaki V
      • Tzanakis N
      • Thalassinos N
      Bouros D. Respiratory muscle strength in hypothyroidism.
      ). In a previous propensity score matching analysis of patients from a New York health system, adjusted for age, sex, race, body mass index, smoking status, and number of comorbidities, hypothyroidism was not associated with an increased risk of mechanical ventilation (adjusted OR: 1.17 [95% CI: 0.81–1.69]) or death (adjusted OR: 1.07 [95% CI: 0.75–1.54]). However, this analysis was limited by the sample size of patients who were hospitalized, by limited number of events, and by fixed selection of 3 controls per case, which forces selection of controls (
      • van Gerwen M
      • Alsen M
      • Little C
      • Barlow J
      • Naymagon L
      • Tremblay D
      • et al.
      Outcomes of Patients With Hypothyroidism and COVID-19: A Retrospective Cohort Study.
      ) The other previous cohort studies and case series were also limited by small sample sizes and lack of controls (
      • Allam MM
      • El-Zawawy HT
      • Ahmed SM
      • Aly Abdelhamid M.
      Thyroid disease and covid-19 infection: Case series.
      ,
      • Bakshi SS
      • Kalidoss VK.
      Is there an association between hypothyroidism and COVID 19?: A preliminary report.
      ,
      • Daraei M
      • Hasibi M
      • Abdollahi H
      • Mirabdolhagh Hazaveh M
      • Zebaradst J
      • Hajinoori M
      • et al.
      Possible role of hypothyroidism in the prognosis of COVID-19.
      ,
      • van Gerwen M
      • Alsen M
      • Little C
      • Barlow J
      • Naymagon L
      • Tremblay D
      • et al.
      Outcomes of Patients With Hypothyroidism and COVID-19: A Retrospective Cohort Study.
      ,
      • Lui DTW
      • Lee CH
      • Chow WS
      • Lee ACH
      • Tam AR
      • Fong CHY
      • et al.
      Thyroid Dysfunction in Relation to Immune Profile, Disease Status, and Outcome in 191 Patients with COVID-19.
      ,
      • Tsivgoulis G
      • Fragkou PC
      • Karofylakis E
      • Paneta M
      • Papathanasiou K
      • Palaiodimou L
      • et al.
      Hypothyroidism is associated with prolonged COVID-19-induced anosmia: a case-control study.
      ,
      • Zhang Y
      • Lin F
      • Tu W
      • Zhang J
      • Choudhry AA
      • Ahmed O
      • et al.
      Thyroid dysfunction may be associated with poor outcomes in patients with COVID-19.
      ). In this study, a caliper width of 0.17 was used for the matched analysis. It is considered conservative and restricts the selection of controls that are indeed similar to the cases, as recommended (
      • Austin PC.
      Optimal caliper widths for propensity-score matching when estimating differences in means and differences in proportions in observational studies.
      ). Due to a successful matched analysis between samples, it is unlikely that age, sex, or other underlying diseases have interfered with the results, although patients with hypothyroidism showed a higher prevalence for coronary artery disease and chronic kidney disease. Medications used during hospitalization were also similar in both groups and therefore cannot explain the difference in prognosis as well.
      This study has limitations to be addressed. It is a pragmatic study based on data from chart review. Thyroid disease status was based on patients’ information given at hospital admission, and therefore, it was not possible to know if the hypothyroidism was compensated. Nevertheless, to the best of our knowledge, this study has the largest sample of patients with COVID-19 with hypothyroidism published so far. TSH and thyroid hormone (T4 and T3) levels were not evaluated during the time of hospitalization and time in the ICU, as the health organizations recommend against testing for thyroid dysfunction during an acute illness, unless it is suspected the acute illness is due to thyroid dysfunction ((
      • Van den Berghe G.
      Non-thyroidal illness in the ICU: a syndrome with different faces.
      ,

      National Institute for Health and Care Excellence. Thyroid disease: assessment and management (NG145). 2019. Available from https://www.nice.org.uk/guidance/ng145

      ), and it was not our aim to access the effects of NTIS. The assessment of thyroid hormone levels throughout the course of COVID-19 is still challenging owing to the possibility of overdiagnosis due to abnormal hormone levels during acute systemic disease. It is important to emphasize that these hormonal changes are adaptive processes and cannot be defined as a disease itself.

      Conclusion

      In this multicenter cohort of patients with COVID-19, those with underlying hypothyroidism had similar comorbidities, clinical presentation, and laboratory examinations as the control group. It was found, nonetheless, that a lower proportion of patients with hypothyroidism required mechanical ventilation and had a trend of lower in-hospital mortality. Therefore, hypothyroidism does not seem to be associated with a worse prognosis and should not be considered among the comorbidities that indicate a risk factor for COVID-19 severity.

      Ethics approval

      The study has been conducted by a protocol approved by the National Commission for Research Ethics(
      • Barreto PA
      • Braga AS
      • Andrade M.
      Evaluation of completeness of dengue records: exploratory study of compulsory notices.
      ) (CAAE 30350820.5.1001.0008). Individual informed consent was waived due to the pandemic and to the fact that all data collected were unidentified and gathered through medical records.

      Availability of data and materials

      Data are available upon reasonable request.

      Competing interests

      The authors declare no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

      Funding

      This study was supported in part by Minas Gerais State Agency for Research and Development (Fundação de Amparo à Pesquisa do Estado de Minas Gerais - FAPEMIG) [grant number APQ-00208-20], National Institute of Science and Technology for Health Technology Assessment (Instituto de Avaliação de Tecnologias em Saúde – IATS)/ National Council for Scientific and Technological Development (Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq) [grant number 465518/2014-1 and 147122/2021-0].
      DNP was funded by a research scholarship from IATS/CNPq [grant number 147122/2021-0].

      Role of the funder/sponsor

      The sponsors had no role in study design; data collection, management, analysis, and interpretation; writing the manuscript; and the decision to submit it for publication. DNP, LFGS, MMMG, MSM, and MCP had full access to all the data in the study and had responsibility for the decision to submit for publication.

      Authors contributions

      Substantial contributions for the conception or design of the manuscript: MSM, DNP, LFGS, and MMMG.
      Substantial contributions for data acquisition, analysis, or interpretation: all authors.
      Manuscript formulation: MSM, DNP, LFGS, MMMG, and MCP.
      Critically revised the manuscript in relation to the important intellectual content: all authors.
      Final version's approval: all authors agreed to be responsible for all aspects of the work, ensuring that issues related to precision of integrity in any of the work's parts will be properly investigated and solved: MSM and MCP.

      Transparency declaration

      The lead authors (DNP, MCP, and MSM) affirm that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as originally planned (and, if relevant, registered) have been explained.

      Competing interests

      The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

      Acknowledgments

      We would like to thank the hospitals that are part of this collaboration for supporting this project: Hospitais da Rede Mater Dei; Hospital das Clínicas da UFMG; Hospital de Clínicas de Porto Alegre; Hospital Santo Antônio; Hospital Eduardo de Menezes; Hospital Tacchini; Hospital Márcio Cunha; Hospital Metropolitano Dr. Célio de Castro; Hospital Metropolitano Odilon Behrens; Hospital Risoleta Tolentino Neves; Hospital Santa Rosália; Hospital Santa Cruz; Hospital São João de Deus; Hospital Semper; Hospital Unimed-BH; Hospital Universitário Canoas; Hospital Universitário Santa Maria; Hospital Moinhos de Vento; Hospital Luxemburgo; Instituto Mario Penna; Hospital Nossa Senhora da Conceição; Hospital João XXIII; Hospital Júlia Kubitschek; Hospital Mãe de Deus; Hospital Regional do Oeste; Hospital das Clínicas da Faculdade de Medicina de Botucatu;Hospital Universitário Ciências Médicas; Hospital Bruno Born; Hospital SOS Cárdio; Hospital São Lucas da PUCRS.
      We also thank all the clinical staff at those hospitals who cared for the patients and all undergraduate students who helped with data collection.

      Appendix. Supplementary materials

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