MANAGEMENT OF ENDOCRINE DISEASE: Subclinical thyrotoxicosis: prevalence, causes and choice of therapy

Relation between iodine nutrition and thyroid diseases in Qinghai, China

Objective

To investigate the adult iodine nutrition and the prevalence of thyroid diseases in Qinghai Province, and analyze the correlation between iodine and thyroid diseases, so as to provide a basis for adjusting the salt iodization plan in Qinghai Province.

Methods

Using cluster and stratified sampling method to select 2628 permanent residents over 18 years old in Qinghai Province for questionnaire survey, physical examination, thyroid color ultrasound, and laboratory index detection.

Results

1. The coverage of iodized salt in adults is 99.71%. 2. The detection rates of thyroid disorders in adults were as follows: Clinical hyperthyroidism was 1.20%, subclinical hyperthyroidism was 0.20%, clinical hypothyroidism was 1.00%, subclinical hypothyroidism was 29.20%, and the goiter was 2.10%. The percentages positivity of TPO Ab, TG Ab, goiter was 9.80%, 9.20%, 2.10%, respectively. Among them single thyroid nodule was 6.40%, multi-nodule thyroid gland was 1.80%. 3. The percentages of mild iodine deficiency, moderate iodine deficiency, Severe iodine deficiency, adequate iodine intake (AI), more than adequate iodine intake (MAI)and excessive iodine intake (EI)were 8.41%, 2.17%, 0.26%, 33.22%, 28.35%, and 27.59%, respectively. The percentages of mild, moderate and severe iodine deficiency in urban populations (7.13%, 0.87%, 0.0%) were significantly lower than those in rural populations (9.81%, 3.59%, 0.56%) (P < 0.05), and the rates of adequate, more than adequate iodine intake in urban populations (36.03%, 30.93%) were significantly higher than that in rural populations (30.14%, 25.52%). The rate of excess iodine intake was higher in rural areas (30.38%) than in urban areas (25.04%). 4. The positive rates of subclinical hypothyroidism, goiter, TPO Ab and TG Ab in female adults (35.28%, 3.39%, 13.54%, 13.94%) were higher than those in male adults (23.58%, 0.96%, 6.266%, 4.79%). The detection rate of single thyroid nodules was higher in urban (8.01%) than rural populations (4.70%), while the detection rate of hypothyroidism, subclinical hypothyroidism, and goiter (0.58%, 25.84%, 1.38%) was lower than that in rural populations (1.52%, 32.96%, 2.96%) (P<0.05). 5. There was no statistical significance in the detection rates of clinical hyperthyroidism, subclinical hypothyroidism, subclinical hypothyroidism, goiter, thyroid nodules, TPO Ab and TG Ab positive rates in different iodine nutritional status (P>0.05). The positive rate of hypothyroidism in the iodine deficiency group is higher than in other iodine nutrition groups.

Conclusion

The nutritional status of iodine in Qinghai Province is iodine excess. Subclinical hypothyroidism was detected at a high rate. Subclinical hypothyroidism, goiter, TPO Ab, and TG Ab were more common in female than in male. The proportion of mild, moderate, and severe iodine deficiency was higher in urban areas than in rural areas. The detection rate of thyroid nodules was higher in urban than in rural areas, and that of hypothyroidism, subclinical hypothyroidism, and goiter was lower than that in rural populations. The detection rate of clinical hypothyroidism was statistically significant in different iodine nutritional states (P< 0.05).

The role of systemic immune activation in the development of thyroid dysfunction in COVID-19

Background. The research of cytokine-induced thyropathies in the midst of continuing coronavirus infection (COVID-19) pandemic is a very important and urgent problem. On the one hand, COVID-19 is often accompanied by a massive overproduction of cytokines, so we can expect an enhanced cytokines effects impact on the thyroid gland. On the other hand, it is possible that biological therapy with tocilizumab, which has a powerful immunosuppressive effect, plays a protective role to the development of cytokines-induced thyropathies amidst COVID-19. The results of the study should be the starting point for understanding the mechanisms of possible compromise of thyroid function during COVID-19. Aim. The primary endpoint is to assess the relationship between the levels of thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) with the inflammatory process markers. The secondary endpoint is the identification of an association between TSH, FT3 and FT4 values, and patient survival. Materials and methods. This retrospective, single-center study included 122 patients hospitalized at the National Medical Research Center for Endocrinology with a clinical and laboratory analysis of COVID-19 and bilateral polysegmental viral pneumonia. To assess the functional status of the thyroid gland all patients underwent observation of the TSH, FT3, FT4, antibodies to thyroid peroxidase, antibodies to the TSH receptor (AT-recTSH). The markers of the inflammatory process were assessed: interleukin-6, C-reactive protein, the degree of lung tissue damage according to multispiral computed tomography of the lungs, the percentage of blood oxygen saturation (SpO2), the treatment outcomes. Results. Five (4%) patients were found with subclinical thyrotoxicosis. Serum TSH values were inversely correlated with interleukin-6 (r=-0.221; p=0.024). Analysis of the level of hospital mortality, stratified by TSH, revealed statistically significantly lower TSH values in the group of deceased patients (p=0.012). The median TSH in surviving patients was 1.34 [0.85; 1.80], for the deceased 0.44 [0.29; 0.99]. Conclusion. Our research shows that the trigger of thyropathies in coronavirus infection is most likely thyroid tissue damage by the proinflammatory cytokines. This study shows some specific clinical aspects regarding the clinical relevance in patients with thyrotoxicosis and COVID-19, namely, the high hospital mortality rate.

Thyroid Dysfunction and COVID-19: The Emerging Role of Selenium in This Intermingled Relationship

COVID-19 represents a worldwide public health emergency, and, beyond the respiratory symptoms characterizing the classic viral disease, growing evidence has highlighted a possible reciprocal relationship between SARS-CoV-2 infection and thyroid dysfunction. The updated data discussed in this review suggests a role of SARS-CoV-2 infection on the thyroid gland, with multiple thyroid pictures described. Conversely, no conclusion can be drawn on the association between pre-existing thyroid disease and increased risk of SARS-CoV-2 infection. In this scenario, selenium (Se), an essential trace element critical for thyroid function and known as an effective agent against viral infections, is emerging as a potential novel therapeutic option for the treatment of COVID-19. Large multicentre cohort studies are required to elucidate the mechanisms underlying thyroid dysfunction during or following recovery from COVID-19, including Se status. Meanwhile, clinical trials should be performed to evaluate whether adequate intake of Se can help address COVID-19 in Se-deficient patients, also avoiding thyroid complications that can contribute to worsening outcomes during infection.

The Association Between Subclinical Thyroid Dysfunction and Recurrence of Atrial Fibrillation After Catheter Ablation

Objective

The aim of this study was to evaluate the association between subclinical thyroid dysfunction and the recurrence of atrial fibrillation (AF) after radiofrequency catheter ablation (RFCA).

Methods

We examined the association between subclinical thyroid dysfunction and the recurrence of AF at a large university-affiliated cardiac arrhythmia center in China. Data were collected from consecutive patients who underwent RFCA for AF, excluding those with a history of hypothyroidism, hyperthyroidism, or ongoing medical treatment for hypothyroidism or hyperthyroidism, biochemically defined overt thyroid disease, and long-term use of amiodarone before admission. The primary end point was the recurrence of AF in a time-to-event analysis. We compared outcomes in patients who had subclinical hyperthyroidism or hypothyroidism with those who had euthyroid state, using a multivariable Cox model with inverse probability weighting and propensity score matching.

Results

In all, 93 patients were excluded from 435 consecutive patients who underwent RFCA for AF. Of the remaining 342 patients for the analysis, the prevalence of subclinical hyperthyroidism and subclinical hypothyroidism were 26 (7.6%) and 41 (12.0%), respectively; during a median follow-up of 489 days, 91 patients (26.6%) developed a primary end point event. In the main analysis of the multivariable Cox model, only subclinical hyperthyroidism [hazard ratio: 3.07, 95% confidence interval (CI): 1.54–6.14] was associated with an increased risk of end point event after adjusting for potential confounders. However, the association between subclinical hypothyroidism and the end point event was not significant (hazard ratio: 0.66, 95% CI: 0.31–1.43). Results were consistent either in multiple sensitivity analyses or across all subgroups of analysis. Compared with individuals with free triiodothyronine (fT3) in the lowest quintile, those with fT3 in the highest quintile had an HR of 2.23 (95% CI: 1.16–4.28) for recurrence of AF. With the increase of thyroid-stimulating hormone (TSH), a reduction in the risk of recurrence of AF was detected in the adjusted model, and the hazard ratio (HR) per standard deviation (SD) increase was 0.82 (95% CI: 0.68–0.98).

Conclusion

In this retrospective cohort study involving patients who underwent RFCA for AF, patients with subclinical hyperthyroidism were associated with a markedly higher prevalence of recurrence of AF, whereas patients with subclinical hypothyroidism had a similar recurrence rate of AF compared to those with the euthyroid state.

Thyroid Disease and Hepatocellular Carcinoma Survival: A Danish Nationwide Cohort Study

<b><i>Introduction:</i></b> Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer mortality worldwide. Recent animal studies suggest that thyroid hormone treatment improves HCC prognosis. The aim of this study was to describe the association between thyroid disease and HCC prognosis in humans. <b><i>Methods:</i></b> We performed a nationwide cohort study including all persons with an HCC diagnosis from 2000 to 2018. Patients’ age, sex, HCC treatment, and diagnoses of thyrotoxicosis, nontoxic goiter, and myxedema were obtained from Danish national healthcare registries. We used regression models to examine the association between thyroid disease and mortality hazard and restricted mean survival time after HCC diagnosis, adjusting for confounding by sex and age. <b><i>Results:</i></b> We included 4,812 patients with HCC and 107 patients with thyroid disease. Median follow-up time was 5 months (total 5,985 person-years). The adjusted mortality hazard ratio was 0.68 (95% CI: 0.47–0.96) for thyrotoxicosis and 0.60 (95% CI: 0.41–0.88) for nontoxic goiter. The restricted mean survival time during the 5 years following HCC diagnosis was 6.8 months (95% CI: 1.1–12.6) longer for HCC patients with thyrotoxicosis than for patients without thyroid disease, and it was 6.9 months (95% CI: 0.9–12.9) longer for HCC patients with nontoxic goiter than for patients without thyroid disease. <b><i>Conclusions:</i></b> In this large nationwide cohort study, thyrotoxicosis and nontoxic goiter were associated with prolonged HCC survival.

Decision Making in Subclinical Thyroid Disease

Subclinical thyroid disease is frequently encountered in clinic practice. Although overt thyroid dysfunction has been associated with adverse clinical outcomes, uncertainty remains about the implications of subclinical thyroid disease. Available data suggest that subclinical hypothyroidism may be associated with increased risk of cardiovascular disease and death. Despite this finding, treatment with thyroid hormone has not been consistently demonstrated to reduce cardiovascular risk. Subclinical hyperthyroidism has been associated with increased risk of atrial fibrillation and osteoporosis, but the association with cardiovascular disease and death is uncertain. The decision to treat depends on the degree of thyroid-stimulating hormone suppression and underlying comorbidities.

Thyroid function in COVID-19 and the association with cytokine levels and mortality

The hypothalamic-pituitary-thyroid hormone axis might be affected in COVID-19, but existing studies have shown varying results. It has been hypothesized that hyperinflammation, as reflected by the secretion of cytokines, might induce thyroid dysfunction among patients with COVID-19. We explored thyroid hormone involvement in the acute phase of symptomatic COVID-19 and its possible associations with cytokine levels and mortality risk. This was a single-center study of 116 consecutive patients hospitalized for moderate-to-severe COVID-19 disease. Serum concentrations of thyroid-stimulating hormone (TSH), free thyroxine (T4), and 45 cytokines/chemokines were measured in all patients within 3 days of admission. Data were extracted retrospectively through a manual review of health records. At admission, 95 (81.9%) were euthyroid; while 21 (18.1%) had biochemically thyroid dysfunction including subclinical thyrotoxicosis (n = 11), overt thyrotoxicosis (n = 2), hypothyroidism (n = 1), non-thyroidal illness (n = 2), and normal TSH but high free T4 (n = 5). TSH levels were inversely correlated with IL-8 (rs = -0.248), IL-10 (rs = -0.253), IL-15 (rs = -0.213), IP-10 (rs = -0.334), and GM-CSF (rs = -0.254). Moreover, IL-8 levels, IP-10, and GM-CSF were significantly higher in patients with serum TSH < 0.4 mIU/L. Lastly, a two-fold increment of IL-8 and IL-10 was associated with significantly higher odds of having TSH < 0.4 mIU/L (odds ratio 1.86 (1.11-3.10) and 1.78 (1.03-3.06)). Serum TSH was not associated with 30- or 90-day mortality. In conclusion, this study suggests that fluctuations of TSH levels in patients with COVID-19 may be influenced by circulating IL-8, IL-10, IL-15, IP-10, and GM-CSF as previously described in autoimmune thyroid diseases.

Metabolic Changes after Radioiodine Correction of Grade 1 and Grade 2 Subclinical Hyperthyroidism

OBJECTIVE

Endogenous subclinical hyperthyroidism (eSCH) is defined by subnormal serum thyroid-stimulating hormone (TSH) level. There is limited evidence of metabolic changes induced by eSCH. The aim of our work was to evaluate changes in BMI and lipid parameters after radioiodine treatment in patients with grade 1 (TSH: 0.1-0.39 mlU/L) and 2 (TSH <0.1 mlU/L) eSCH.

DESIGN

A retrospective study was performed on 74 patients with eSCH caused by benign autonomous nodular goiter which was treated with radioiodine.

METHODS

We assessed BMI, lipids parameters, and TSH after radioiodine therapy. The 12-month follow-up time point was used to compare the primary outcome variables. TSH was measured by the electrochemiluminescence method.

RESULTS

After radioiodine therapy, the absolute and relative increases in BMI at 12 months were significantly higher in the grade 2 group than in the grade 1 group (1.07 ± 0.27 kg/m² vs. 0.26 ± 0.15 kg/m², respectively; p = 0.023 and 4.01 ± 0.98% vs. 1.01 ± 0.56%, respectively; p = 0.026). Compared to baseline, significant increases in the levels of total cholesterol and LDL were observed after treatment in the grade 2 eSCH group (16.7 ± 4.5 mg/dL p < 0.01 and 14.3 ± 4.1 mg/dL p < 0.01, respectively) but not in the grade 1 group. In a multivariate model, a negative correlation was observed between pretreatment TSH levels and absolute BMI gain (p < 0.01).

CONCLUSIONS

After correction of eSCH, increases in BMI and LDL levels were observed only in patients with grade 2 eSCH. Pretreatment serum TSH was the main independent factor associated with BMI changes after radioiodine treatment.

The Association with Subclinical Thyroid Dysfunction and Uric Acid

The relationship between subclinical thyroid dysfunction and uric acid was not well established. This study aimed to determine if subclinical thyroid dysfunction is associated with hyperuricemia risk and to evaluate the levels of uric acid in patients with different forms of subclinical thyroid dysfunction. A systematic search was conducted in 4 databases to obtain relevant studies on subclinical thyroid dysfunction (subclinical hyperthyroidism and subclinical hypothyroidism) and uric acid. The standardized mean difference (SMD) or odds ratio (OR) and 95% confidence interval (95% CI) were used for evaluation, and the sensitivity analysis was conducted. Publication bias was estimated by funnel plot, Egger's test, and Begg's test. A total of 73 studies were included in this meta-analysis. The results demonstrated that serum levels of uric acid in patients with subclinical hypothyroidism were significantly higher than those of controls and patients with subclinical hyperthyroidism. Patients with subclinical thyroid dysfunction had a higher prevalence of hyperuricemia compared with normal clinical thyroid function. Subclinical thyroid dysfunction was associated with the prevalence of hyperuricemia. Different types of subclinical thyroid dysfunction had varied effects on serum levels of uric acid.

Thyrotoxicosis in patients with COVID-19: the THYRCOV study

OBJECTIVE

This study assessed thyroid function in patients affected by the coronavirus disease-19 (COVID-19), based on the hypothesis that the cytokine storm associated with COVID-19 may influence thyroid function and/or the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may directly act on thyroid cells, such as previously demonstrated for SARS-CoV-1 infection.

DESIGN AND METHODS

This single-center study was retrospective and consisted in evaluating thyroid function tests and serum interleukin-6 (IL-6) values in 287 consecutive patients (193 males, median age: 66 years, range: 27-92) hospitalized for COVID-19 in non-intensive care units.

RESULTS

Fifty-eight patients (20.2%) were found with thyrotoxicosis (overt in 31 cases), 15 (5.2%) with hypothyroidism (overt in only 2 cases), and 214 (74.6%) with normal thyroid function. Serum thyrotropin (TSH) values were inversely correlated with age of patients (rho -0.27; P < 0.001) and IL-6 (rho -0.41; P < 0.001). In the multivariate analysis, thyrotoxicosis resulted to be significantly associated with higher IL-6 (odds ratio: 3.25, 95% confidence interval: 1.97-5.36; P < 0.001), whereas the association with age of patients was lost (P = 0.09).

CONCLUSIONS

This study provides first evidence that COVID-19 may be associated with high risk of thyrotoxicosis in relationship with systemic immune activation induced by the SARS-CoV-2 infection.

Radioiodine Therapy-Induced Conversion of Toxic Adenoma to Graves’ Disease

We present a 50-year-old female who was evaluated for the symptoms of thyrotoxicosis. She had low thyroid stimulating hormone (TSH) 0.02 with normal free thyroxine (FT4) 1.00 (0.61-1.76 ng/dL) and normal total triiodothyronine (TT3) 1.0 (0.60-2.20 ng/mL) levels. Her thyrotropin receptor antibody (TRAbs) and thyroid peroxidase antibody (TPOAb) titers were negative. Thyroid ultrasound revealed an ill-defined, heterogeneous, 1.8 cm x 0.8 cm x 0.7 cm nodule in the left lower lobe. 123-radioiodine (RAI) thyroid scan revealed 38.5% uptake, which was concentrated in the lower left thyroid lobe, a finding consistent with a solitary toxic adenoma of the thyroid.

The patient became clinically and biochemically euthyroid on methimazole (MMI). She then underwent 131-RAI therapy with 12 mCi, which cured her hyperthyroidism with normalization of TSH levels for four months. She then developed overt thyrotoxicosis with low TSH of 0.02, elevated TT3 of 3.2, and normal FT4 of 0.91. Repeat TRAbs and TPOAb were elevated along with diffusely increased uptake on the I-123 RAI thyroid uptake scan, consistent with Graves’ disease (GD). The patient was then placed on MMI again to bridge to definitive treatment with total thyroidectomy. Our case is a rare case where the patient with solitary toxic adenoma with negative TPOAb serology developed GD following I-131 RAI treatment.

Hyperthyroidism

Thyrotoxicosis is a general term for excess circulating and tissue thyroid hormone levels, whereas hyperthyroidism specifically denotes disorders involving a hyperactive thyroid gland (Graves disease, toxic multinodular goiter, toxic adenoma). Diagnosis and determination of the cause rely on clinical evaluation, laboratory tests, and imaging studies. Hyperthyroidism is treated with antithyroid drugs, radioactive iodine ablation, or thyroidectomy. Other types of thyrotoxicosis are monitored and treated with β-blockers to control symptoms given that most of these conditions resolve spontaneously.

Heterogenous biochemical expression of hormone activity in subclinical/overt hyperthyroidism and exogenous thyrotoxicosis

Background

Subclinical hyperthyroidism/thyrotoxicosis originates from different causes and clinical conditions, sharing the laboratory constellation of a suppressed TSH in the presence of thyroid hormone concentrations within the reference range.

Aim

Presentation of hyperthyroidism can manifest itself in several ways. We questioned whether there is either a consistent biochemical equivalence of thyroid hormone response to these diagnostic categories, or a high degree of heterogeneity may exist both within and between the different clinical manifestations.

Methods

This secondary analysis of a former prospective cross-sectional trial involved 461 patients with untreated thyroid autonomy, Graves’ disease or on levothyroxine (LT4) after thyroidectomy for thyroid carcinoma. TSH response and biochemical equilibria between TSH and thyroid hormones were contrasted between endogenous hyperthyroidism and thyrotoxicosis (LT4 overdose).

Results

Concentrations of FT4, FT3, TSH, deiodinase activity and BMI differed by diagnostic category. Over various TSH strata, FT4 concentrations were significantly higher in LT4-treated thyroid carcinoma patients, compared to the untreated diseases, though FT3 levels remained comparable. They were concentrated in the upper FT4- but low deiodinase range, distinguishing them from patients with thyroid autonomy and Graves’ disease. In exogenous thyrotoxicosis, TSH and FT3 were less responsive to FT4 concentrations approaching its upper normal/hyperthyroid range.

Conclusions

The presence or lack of TSH feedforward activity determines the system response in the thyroid-active (hyperthyroidism) and no-thyroid response to treatment (thyrotoxicosis). This rules out a consistent thread of thyroid hormone response running through the different diagnostic categories. TSH measurements should therefore be interpreted conditionally and differently in subclinical hyperthyroidism and thyrotoxicosis.

Graves' disease, multinodular goiter and subclinical hyperthyroidism

Subclinical hyperthyroidism is a common clinical entity, defined by serum TSH below the reference range, with normal FT4 and FT3 levels in an asymptomatic patient. Whether or not subclinical hyperthyroidism should be treated remains a matter of debate. Cross-sectional and longitudinal population-based studies demonstrate association of subclinical hyperthyroidism with risk of atrial fibrillation and osteoporosis, and with cardiovascular and all-cause mortality. However, there are no randomized clinical trials addressing whether long-term health outcomes are improved by treating subclinical hyperthyroidism; in the absence of evidence one way or the other, it seems appropriate to use decision trees taking account of TSH concentration and presence of risk factors (age>65 years or post-menopause, osteoporosis and cardiac disease).

Global epidemiology of hyperthyroidism and hypothyroidism

Thyroid hormones are essential for growth, neuronal development, reproduction and regulation of energy metabolism. Hypothyroidism and hyperthyroidism are common conditions with potentially devastating health consequences that affect all populations worldwide. Iodine nutrition is a key determinant of thyroid disease risk; however, other factors, such as ageing, smoking status, genetic susceptibility, ethnicity, endocrine disruptors and the advent of novel therapeutics, including immune checkpoint inhibitors, also influence thyroid disease epidemiology. In the developed world, the prevalence of undiagnosed thyroid disease is likely falling owing to widespread thyroid function testing and relatively low thresholds for treatment initiation. However, continued vigilance against iodine deficiency remains essential in developed countries, particularly in Europe. In this report, we review the global incidence and prevalence of hyperthyroidism and hypothyroidism, highlighting geographical differences and the effect of environmental factors, such as iodine supplementation, on these data. We also highlight the pressing need for detailed epidemiological surveys of thyroid dysfunction and iodine status in developing countries.

Endocrine disorders and the cerebellum: from neurodevelopmental injury to late-onset ataxia

Hormonal disorders are a source of cerebellar ataxia in both children and adults. Normal development of the cerebellum is critically dependent on thyroid hormone, which crosses both the blood-brain barrier and the blood-cerebrospinal fluid barrier thanks to specific transporters, including monocarboxylate transporter 8 and the organic anion-transporting polypeptide 1C1. In particular, growth and dendritic arborization of Purkinje neurons, synaptogenesis, and myelination are dependent on thyroid hormone. Disturbances of thyroid hormone may also impact on cerebellar ataxias of other origin, decompensating or aggravating the pre-existing ataxia manifesting with motor ataxia, oculomotor ataxia, and/or Schmahmann syndrome. Parathyroid disorders are associated with a genuine cerebellar syndrome, but symptoms may be subtle. The main conditions combining diabetes and cerebellar ataxia are Friedreich ataxia, ataxia associated with anti-GAD antibodies, autoimmune polyglandular syndromes, aceruloplasminemia, and cerebellar ataxia associated with hypogonadism (especially Holmes ataxia/Boucher-Neuhäuser syndrome). The general workup of cerebellar disorders should include the evaluation of hormonal status, including thyroid-stimulating hormone and free thyroxine levels, and hormonal replacement should be considered depending on the laboratory results. Cerebellar deficits may be reversible in some cases.