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Abstract Context The effects of COVID-19 on the thyroid axis remain uncertain. Recent evidence has been conflicting, with both thyrotoxicosis and suppression of thyroid function reported. Objective We aimed to detail the acute effects of COVID-19 on thyroid function and determine if these effects persisted on recovery from COVID-19. Design A cohort observational study was conducted. Participants and Setting Adult patients admitted to Imperial College Healthcare National Health Service Trust, London, UK, with suspected COVID-19 between March 9 to April 22, 2020, were included, excluding those with preexisting thyroid disease and those missing either free thyroxine (FT4) or thyrotropin (TSH) measurements. Of 456 patients, 334 had COVID-19 and 122 did not. Main Outcome Measures TSH and FT4 measurements were recorded at admission, and where available, in 2019 and at COVID-19 follow-up. Results Most patients (86.6%) presenting with COVID-19 were euthyroid, with none presenting with overt thyrotoxicosis. Patients with COVID-19 had a lower admission TSH and FT4 compared to those without COVID-19. In the COVID-19 patients with matching baseline thyroid function tests from 2019 (n = 185 for TSH and 104 for FT4), TSH and FT4 both were reduced at admission compared to baseline. In a complete case analysis of COVID-19 patients with TSH measurements at follow-up, admission, and baseline (n = 55), TSH was seen to recover to baseline at follow-up. Conclusions Most patients with COVID-19 present with euthyroidism. We observed mild reductions in TSH and FT4 in keeping with a nonthyroidal illness syndrome. Furthermore, in survivors of COVID-19, thyroid function tests at follow-up returned to baseline.

Abstract Both hyperthyroidism and hypothyroidism can have adverse effects in pregnancy. The most common causes of thyrotoxicosis in pregnancy are gestational transient thyrotoxicosis and Graves’ disease. It is important to distinguish between these entities as treatment options differ. Women of reproductive age who are diagnosed with Graves’ disease should be counseled regarding the impact of treatment options on a potential pregnancy. Although the absolute risk is small, antithyroid medications can have teratogenic effects. Propylthiouracil appears to have less severe teratogenicity compared to methimazole and is therefore favored during the first trimester if a medication is needed. Women should be advised to delay pregnancy for at least 6 months following radioactive iodine to minimize potential adverse effects from radiation and ensure normal thyroid hormone levels prior to conception. As thyroid hormone is critical for normal fetal development, hypothyroidism is associated with adverse obstetric and child neurodevelopmental outcomes. Women with overt hypothyroidism should be treated with levothyroxine (LT4) to a thyrotropin (thyroid-stimulating hormone; TSH) goal of <2.5 mIU/L. There is mounting evidence for associations of maternal hypothyroxinemia and subclinical hypothyroidism with pregnancy loss, preterm labor, and lower scores on child cognitive assessment. Although there is minimal risk of LT4 treatment to keep TSH within the pregnancy-specific reference range, treatment of mild maternal thyroid hypofunction remains controversial, given the lack of clinical trials showing improved outcomes with LT4 treatment.

Abstract Context The effects of maternal subclinical hypothyroidism on pregnancy outcomes are not clear. Objective We aimed to assess potential associations between maternal thyrotropin (thyroid-stimulating hormone [TSH]) levels in pregnancy and obstetric and perinatal outcomes. Design Retrospective cohort study. Setting Tertiary academic medical center. Patients Women aged ≥18 years with a singleton gestation and no known thyroid disease seen for prenatal care at Boston Medical Center from January 1, 2003 through May 22, 2014, and their fetuses and infants were included. Main Outcome Measures Risk ratios of adverse obstetric and perinatal outcomes. Results A total of 8,413 pregnant women (mean age 29.1 years, 15% white, 60% black, 13% Hispanic) and their fetuses and infants (mean gestational age at birth 38.5 weeks, 52% male, mean birth weight 3.2 kg) were included in the analyses. The median (interquartile range) TSH level was 1.06(0.62–1.60) mIU/L, and 130 women (1.6%) had TSH > 4 mIU/L. Maternal TSH levels > 4 mIU/L were associated with increased risks of prematurity (risk ratio [RR] 2.17 [95% confidence interval 1.15–4.07] P = .016) and neonatal respiratory distress syndrome (RDS) (RR 2.83 [95% confidence interval 1.02–7.86] P = .046) compared to TSH levels ≤ 4 mIU/L. Although not statistically significant, TSH levels > 4 mIU/L were also associated with increased RRs for fetal loss, preeclampsia/eclampsia, and low birth weight. TSH levels > 4 mIU/L were not associated with preterm labor, placental abruption, cesarean section, gestational hypertension or diabetes, or neonatal intensive care unit admission. Conclusion Maternal serum TSH concentration > 4 mIU/L in pregnancy was associated with approximately 2-fold increased risks of prematurity and RDS in offspring. Elevated TSH was also associated with statistically non-significant increases in the risk of fetal loss, preeclampsia/eclampsia, and low birth weight.

Abstract Context The COVID-19 pandemic continues to exert an immense burden on global health services. Moreover, up to 63% of patients experience persistent symptoms, including fatigue, after acute illness. Endocrine systems are vulnerable to the effects of COVID-19 as many glands express the ACE2 receptor, used by the SARS-CoV-2 virion for cellular access. However, the effects of COVID-19 on adrenal and thyroid gland function after acute COVID-19 remain unknown. Objective Our objectives were to evaluate adrenal and thyroid gland function in COVID-19 survivors. Methods A prospective, observational study was undertaken at the Clinical Research Facility, Imperial College NHS Healthcare Trust, including 70 patients ≥18 years of age, at least 3 months after diagnosis of COVID-19. Participants attended a research study visit (8:00-9:30 am), during which a short Synacthen test (250 µg IV bolus) and thyroid function assessments were performed. Results All patients had a peak cortisol ≥450 nmol/L after Synacthen, consistent with adequate adrenal reserve. Basal and peak serum cortisol did not differ according to disease severity or history of dexamethasone treatment during COVID-19. There was no difference in baseline or peak cortisol after Synacthen or in thyroid function tests, or thyroid status, in patients with fatigue (n = 44) compared to those without (n = 26). Conclusion Adrenal and thyroid function ≥3 months after presentation with COVID-19 was preserved. While a significant proportion of patients experienced persistent fatigue, their symptoms were not accounted for by alterations in adrenal or thyroid function. These findings have important implications for the clinical care of patients after COVID-19.

The Mediterranean diet, recognized as being cultural heritage by UNESCO, is mostly plant-based and includes a high consumption of whole-grain, fruit, and vegetables with a moderate consumption of alcohol during meals. Thus, it provides a small amount of saturated fatty acids and a high quantity of antioxidants and fiber. For this reason, it has been considered to have an important role in preventing cardiovascular diseases, chronic kidney diseases, type 2 diabetes mellitus, and cancer, but its relationship with thyroid function and diseases is still under debate. The aim of this review was to search for the possible correlation between the Mediterranean diet and thyroid function, and to critically evaluate the pathophysiological link between selected food intake and thyroid disorders.

Background The association between season and thyroid function parameters has been extensively studied, but the non-linear and lagged effects of extremely low ambient temperature on thyroid function parameters remain unknown. Objective We sought to examine non-linear and lagged patterns in how extremely low ambient temperature is associated with thyroid function parameters. Methods We conducted a panel study based on the data of five thyroid function parameters from the 949th Hospital in Altay City, China, from 2020 to 2023. Mixed-effect modeling with distributed lagged non-linear models (DLNMs) was applied to analyze the data. Results Thyroid function parameters from 1237 individuals were collected during the study period. Compared with the benchmark temperature (8.5°C), free triiodothyronine (FT3) and free thyroxine (FT4) levels increased significantly by 2.01 (95% CI, 0.82, 3.19 pg/mL), and 0.80 (95% CI, 0.24, 1.36 pg/mL) in − 20°C, respectively. While thyroid-stimulating hormone (TSH) level increased by 0.91 μU/mL compared with the benchmark temperature (8.5°C), albeit without a significant difference (95% CI, − 0.50, 2.32). When temperature increased from 20°C to 29°C, total thyroxine (TT4) significantly increased and FT4 significantly decreased. Conversely, the changes in total triiodothyronine (TT3) levels under different temperatures were more subtle. Further subgroup analyses showed that under extremely low ambient temperatures, women had greater increases compared to men in TT4 level and individuals with thyroid disorders had greater increases in TT4, FT4 and FT3 levels than those without thyroid disorders. Conclusions This study provides new epidemiological evidence that extremely low ambient temperatures may affect thyroid function. Therefore, timely protective measures during cold weather may be helpful to maintain stable thyroid function and to reduce the risk of hypothermia and frostbite, especially in people with thyroid disorders.

Objective Physical activity (PA) is closely related to our lives, and the effects of PA on thyroid function have not been elucidated. Methods Using data from the National Health and Nutrition Examination Survey (NHANES) 2007–2012, we included 5877 participants and analyzed the associations of thyroid function with weekly physical activity (PAM, expressed in metabolic equivalents of task) and physical activity time (PAT) in American adults. Univariate and multivariate logistic analyses were used to demonstrate the associations of PAM and PAT with the primary outcome. Linear regression analysis was performed to determine the associations between thyroid biochemical indicators/diseases and PAM/PAT. Results Our study revealed noticeable sex differences in daily PA among the participants. The odds ratio of the fourth versus the first quartile of PAM was 3.07 (confidence interval, CI [1.24, 7.58], p  = 0.02) for overt hypothyroidism, 3.25 (CI [1.12, 9.45], p  = 0.03) for subclinical hyperthyroidism in adult men. PAT in the range of 633–1520 min/week was found to be associated with the occurrence of subclinical hyperthyroidism [ p  < 0.001, OR (95% CI) = 5.89 (1.85, 18.80)], PAT of the range of > 1520 min/week was found to be associated with the occurrence of overt hypothyroidism [ p  < 0.001, OR (95% CI) = 8.70 (2.80, 27.07)] and autoimmune thyroiditis (AIT) [ p  = 0.03, OR (95% CI) = 1.42 (1.03, 1.97)] in adult men. When PAM < 5000 MET*minutes/week or PAT < 1000 min/week, RCS showed an L-shaped curve for TSH and an inverted U-shaped curve for FT4. The changes in FT3 and TT3 in men were linearly positively correlated with PAM and PAT, while TT4 is linearly negatively correlated. Conclusion The amount of daily physical activity of American adults is strongly associated with changes in thyroid function, including thyroid hormone levels and thyroid diseases. Thyroid hormone levels were varied to a certain extent with changes in PAM and PAT.

Objective: Iron deficiency (ID) is the most prevalent nutritional deficiency worldwide. Low levels of serum ferritin (SF) could affect the thyroid gland and its functioning. The purpose of this systematic review and meta-analysis is to summarize the main currently available evidence and analyze data on the relationship between ID and thyroid function. Methods: This study included all articles evaluating the relationship between ID and thyroid function. Quality assessment was performed using Cambridge Quality Checklists. The search strategy included the following combination of Medical Subjects Headings terms and keywords: “iron deficiency”, “thyroid function”, “thyroid disease”, “thyroid dysfunction”, and “hypothyroidism”. A meta-analysis was performed to evaluate whether thyroid stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) levels differed between patients with ID and healthy controls without ID. For statistical comparison between cases and controls, the mean difference (MD) was calculated, and a subgroup analysis of pregnant and non-pregnant women was performed. Cochran’s Q testing and heterogeneity indices (I2) were used to assess statistical heterogeneity. Sensitivity analysis and publication bias analyses were also performed, both qualitatively and quantitatively. Finally, a meta-regression analysis was performed to evaluate the correlation between serum TSH or FT4 levels and SF in the study population. Results: Ten cross-sectional studies were identified and reviewed. Patients with ID showed TSH (MD: −0.24 mIU/L; 95% CI −0.41, −0.07; I2 = 100%, p = 0.005), FT4 (MD: −1.18 pmol/L; 95% CI −1.43, −0.94; I2 = 99%, p < 0.000001), and FT3 (MD: −0.22 pmol/L; 95% CI −0.32, −0.12; I2 = 99%, p < 0.00001) levels that were significantly lower. Subgroup analysis confirmed significantly lower TSH, FT4, and FT3 levels in pregnant women. Non-pregnant women showed significantly lower serum FT4 and FT3 levels but no difference in TSH values. Meta-regression analysis showed that serum TSH and FT4 levels were positively correlated with SF levels. Our systematic review of the literature found that ID significantly increases the prevalence of thyroid autoantibody (anti-thyroglobulin antibodies and anti-thyroid peroxidase antibodies) positivity both individually and collectively. Conclusion: Studies currently published in the literature indicate a possible relationship between ID, thyroid function, and autoimmunity, especially in some patient groups. Data analysis shows that thyroid hormone levels are lower in patients with ID and, in particular, in pregnant women. Further studies are needed to understand the role played by iron in thyroid metabolism.

Background To evaluate the relationship between thyroid function and thyroid homeostasis parameters with the prevalence of chronic kidney disease (CKD) and furtherly explore the all-cause and cardiovascular mortality among individuals with CKD using data from the National Health and Nutrition Examination Survey (NHANES) 2007–2012. Methods This study included 8,526 adults, including 1,625 patients with CKD. Thyroid function included serum free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH). The thyroid homeostasis parameters, including FT3/FT4, thyroid feedback quantile-based index (TFQI FT4 , TFQI FT3 ), thyrotrophic thyroxine resistance index (TT4RI, TT3RI) and thyroid-stimulating hormone index (TSHI) were calculated. Weighted multivariate logistic regression models to explore the association between thyroid function and thyroid homeostasis parameters and the prevalence of CKD. Cox proportional hazards models were used to investigate the association of thyroid function and thyroid homeostasis parameters with all-cause and cardiovascular mortality among CKD patients. Kaplan–Meier curves compared survival across the quartiles of the thyroid function and thyroid homeostasis parameters among CKD patients. Furthermore, the restricted cubic splines were used to explore the non‑linear relationships. Results The weighted multivariate logistic regression models showed that FT4 was positively correlated with the prevalence of CKD, FT3/FT4 and TFQI FT3 were negatively correlated with mortality in patients with CKD. The Cox regression models 3 shows that the multivariate-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of FT3, FT4 and TSH with the all-cause mortality were 0.66(0.47,0.93), 1.07(1.04,1.10) and 1.01(0.98,1.04). At the same time, FT3/FT4 and TFQI FT3 were significantly associated with all-cause mortality after multivariate adjustment. And we further converted thyroid function indicators and thyroid homeostasis parameters from a continuous variable to a categorical variable (quartiles) to conduct the sensitivity analysis. There was no difference in cardiovascular mortality. In crude Kaplan–Meier analyses, there was a U-shaped nonlinear relationship between FT3, TSH, FT3/FT4, TT4RI, TT3RI and TSHI with all-cause mortality, but not FT4, TFQI FT4 and TFQI FT3 . There was an inverted U-shaped relationship between TFQI FT3 and TT4RI with cardiovascular mortality, but not FT3, FT4, TSH, FT3/FT4, TFQI FT4 , TT3RI and TSHI. Conclusions Thyroid function and thyroid parameters are closely related to the prevalence of the CKD and all-cause and cardiovascular mortality among individuals with CKD, and the specific mechanisms still required further in-depth research in the future.

Background Obesity and metabolic syndrome (MetS) have become urgent worldwide health problems, predisposing patients to unfavorable myocardial status and thyroid dysfunction. Low-carbohydrate diet (LCD) and time-restricted eating (TRE) have been confirmed to be effective methods for weight management and improving MetS, but their effects on the myocardium and thyroid are unclear. Methods We conducted a secondary analysis in a randomized clinical diet-induced weight-loss trial. Participants ( N  = 169) diagnosed with MetS were randomized to the LCD group, the 8 h TRE group, or the combination of the LCD and TRE group for 3 months. Myocardial enzymes and thyroid function were tested before and after the intervention. Pearson’s or Spearman’s correlation was assessed between functions of the myocardium and thyroid and cardiometabolic parameters at baseline. Results A total of 162 participants who began the trial were included in the intention-to-treat (ITT) analysis, and 57 participants who adhered to their assigned protocol were involved in the per-protocol (PP) analysis. Relative to baseline, lactate dehydrogenase, creatine kinase MB, hydroxybutyrate dehydrogenase, and free triiodothyronine (FT3) declined, and free thyroxine (FT4) increased after all 3 interventions (both analyses). Creatine kinase (CK) decreased only in the TRE (− 18 [44] U/L, P  < 0.001) and combination (− 22 [64] U/L, P  = 0.003) groups (PP analysis). Thyrotropin (− 0.24 [0.83] μIU/mL, P  = 0.011) and T3 (− 0.10 ± 0.04 ng/mL, P  = 0.011) decreased in the combination group (ITT analysis). T4 (0.82 ± 0.39 μg/dL, P  = 0.046), thyroglobulin antibodies (TgAb, 2 [1] %, P  = 0.021), and thyroid microsomal antibodies (TMAb, 2 [2] %, P  < 0.001) increased, while the T3/T4 ratio (− 0.01 ± 0.01, P  = 0.020) decreased only in the TRE group (PP analysis). However, no significant difference between groups was observed in either analysis. At baseline, CK was positively correlated with the visceral fat area. FT3 was positively associated with triglycerides and total cholesterol. FT4 was negatively related to insulin and C-peptide levels. TgAb and TMAb were negatively correlated with the waist-to-hip ratio. Conclusions TRE with or without LCD confers remarkable metabolic benefits on myocardial status and thyroid function in subjects with MetS. Trial registration ClinicalTrials.gov, NCT04475822.