Iodine intake and the pattern of thyroid disorders: a comparative epidemiological study of thyroid abnormalities in the elderly in Iceland and in Jutland, Denmark

Autoimmune thyroiditis incidence in a large population-based study in northeastern Italy

PURPOSE

An improvement in iodine status in the Veneto region (Italy) in the last decade has been documented. Our aim was to estimate the incidence of autoimmune thyroiditis (AT) in this region over the period 2012-2022.

METHODS

A retrospective population-based study conducted in Veneto using the population registry and administrative health databases. We documented incident hyperthyroidism from 2013 to 2022 to exclude prevalent cases and calculated standardised incidence rates (IR) per 10,000 person-years by age and sex.

RESULTS

We identified 65,379 incident cases (IR: 13.38), 5.44-fold higher in females than in males. IR decreased from 15.86 (95% CI: 15.50, 16.21) in 2013 to 12.35 (95% CI: 12.04, 12.67) in 2022. The decline was evident only in females, with a documented reduction in IR from 27.26 (95% CI: 26.61, 27.91) in 2013 to 20.49 (95% CI: 19.92, 21.07) in 2022 (P = 0.002). The decrease was sharper in females aged 15-54 years (IR from 37.86 (95%CI: 36.79, 38.94) in 2013 to 27.40 (95% CI: 26.44, 28.36) in 2022; P < 0.001) than in those aged ≥55 years (IR from 20.06 (95% CI: 19.13, 20.99) in 2013 to 16.56 (95% CI: 15.78, 17.35) in 2022; P = 0.034). In 2020, an out-of-trend decrease in AT incidence was documented, corresponding with the SARS-CoV-2 pandemic, with a realignment to the trend in the subsequent years.

CONCLUSIONS

A decline in AT was documented in the Veneto region in the last decade, paralleling improvement in the iodine status. The reduction was significant only among females, particularly in reproductive age.

Age-Specific Reference Intervals for Thyroid-Stimulating Hormones and Free Thyroxine to Optimize Diagnosis of Thyroid Disease

Background: Thyroid-stimulating hormone (TSH) and subsequent free thyroxine (FT4) concentrations outside the reference interval (RI) are used to diagnose thyroid diseases. Most laboratories do not provide age-specific RIs for TSH and FT4 beyond childhood, although TSH concentrations vary with age. Therefore, we aimed to establish TSH and FT4 age-specific RIs throughout life and aimed to determine whether using these RIs would result in reclassification of thyroid disease diagnoses in adults. Methods: This multicenter retrospective cross-sectional study used big data to determine indirect RIs for TSH and FT4. These RIs were determined by TMC and refineR-analysis, respectively, using four different immunoassay platforms (Roche, Abbott, Siemens, and Beckman Coulter). Retrospective data (2008-2022) from 13 Dutch laboratories for general practitioners and local hospitals were used. RIs were evaluated per manufacturer. Age groups were established from 2 to 20 years by 2-year categories and decade categories between 20 and 100 years. Results: We included totally 7.6 million TSH and 2.2 million FT4 requests. TSH upper reference limits (URLs) and FT4 lower reference limits were higher in early childhood and decreased toward adulthood. In adulthood, TSH URLs increased from 60 years in men, and from 50 years in women, while FT4 URLs increased from 70 years onward. Using adult age-specific RIs resulted in a decrease in diagnoses of subclinical and overt hypothyroidism in women above 50 and men above 60 years in our Roche dataset. Conclusion: This study stressed the known importance of using age-specific RIs for TSH and FT4 in children. This study also showed the clinical relevance of using age-specific RIs for TSH in adulthood to reduce diagnoses of subclinical hypothyroidism in older persons. Therefore, implementation of adult TSH age-specific RIs should be strongly considered. Data are less uniform regarding FT4 age-specific RIs and more research should be performed before implementing these in clinical practice.

Potential use of seaweed as a dietary supplement to mitigate enteric methane emission in ruminants

Seaweeds or marine algae exhibit diverse morphologies, sizes, colors, and chemical compositions, encompassing various species, including red, green, and brown seaweeds. Several seaweeds have received increased research attention and application in animal feeding investigations, particularly in ruminant livestock, due to their higher yield and convenient harvestability at present. Recent endeavors encompassing both in vitro and in vivo experiments have indicated that many seaweeds, particularly red seaweed (Asparagopsis taxiformis and Asparagopsis armata), contain plant secondary compounds, such as halogenated compounds and phlorotannins, with the potential to reduce enteric ruminal methane (CH4) emissions by up to 99 % when integrated into ruminant diets. This review provides an encompassing exploration of the existing body of knowledge concerning seaweeds and their impact on rumen fermentation, the toxicity of ruminal microbes, the health of animals, animal performance, and enteric ruminal CH4 emissions in both in vitro and in vivo settings among ruminants. By attaining a deeper comprehension of the implications of seaweed supplementation on rumen fermentation, animal productivity, and ruminal CH4 emissions, we could lay the groundwork for devising innovative strategies. These strategies aim to simultaneously achieve environmental benefits, reduce greenhouse gas emissions, enhance animal efficiency, and develop aquaculture and seaweed production systems, ensuring a high-quality and consistent supply chain. Nevertheless, future research is essential to elucidate the extent of the effect and gain insight into the mode of action.

A nationwide registry-based observational study of thyroid disease incidence in the Faroe Islands

OBJECTIVE

The occurrence of thyroid disease varies among populations. While the iodine nutrition level of the Faroese seems to have been decreasing over the past decades, there is no systematic evaluation of the thyroid disease pattern in the Faroe Islands. Such knowledge of thyroid disease occurrence in the North Atlantic region may support healthcare planning and prevention. To investigate incidence rates, including subtypes of thyroid diseases, and demographic characteristics of thyroid disease patients in the Faroe Islands, to improve understanding of the patterns and trends of these disorders.

DESIGN AND METHOD

A registry-based observational study was conducted over 10 years, encompassing all adult Faroese individuals.

PATIENTS AND MEASUREMENTS

Health records from general practitioners and hospitals were used to identify incident cases of thyroid diseases. Validation was performed using multiple data sources. The incidence rates were standardised using population data from the middle of the study period 2006-2018.

RESULTS

Among the 1152 individuals diagnosed with thyroid disease, the standardised incidence rates per 100,000 person-years were 55 for hyperthyroidism and 112 for hypothyroidism, and around four times higher in women than in men. Hashimoto's thyroiditis was the dominant cause of hypothyroidism, while Graves' disease was the leading cause of hyperthyroidism. The incidence of hypothyroidism increases with age. A decreasing trend was observed over time for both hypothyroidism and hyperthyroidism.

CONCLUSION

Considering the decrease in iodine nutrition levels over the past decades, we were surprised by the high incidence of autoimmune thyroid disease. The findings highlight the need for continuous monitoring of thyroid disease occurrence in coastal areas of the North Atlantic Ocean.

Biological variation in thyroid function tests in older adults and clinical implications

OBJECTIVE

Interpreting thyroid function tests can be challenging due to inherent variation, and the need for tests rises with age. While age-related changes in thyrotropin (TSH) levels are known, the biological variation in older adults remains unclear.

DESIGN

We recruited nineteen 65-99-year-old (older adults) without thyroid disease for monthly blood sampling for 1 year.

PATIENTS AND MEASUREMENTS

Serum was stored at -20C°, and TSH, total thyroxine (TT4) and total triiodothyronine (TT3) were analysed in random order in a single batch for each participant. Results were compared to test results from 15 euthyroid men aged 24-53 years (younger adults) collected previously using a similar methodology.

RESULTS

Interindividual coefficients of variation in older/younger adults were 46.7%/44.0% for TSH, 12.7%/19.5% for TT4 and 14.6%/22.4% for TT3. Intraindividual coefficients of variation (CVI ) were 19.0%/25.4% for TSH, 5.5%/10.8% for TT4 and 6.9%/13.2% for TT3. The index of individuality was below 0.6 for all hormones in all age groups. The number of samples required to determine the homoeostatic set-point at 10% precision in older adults was 14-21 for TSH and 2 for TT4 and TT3. TT4 in older adults was the only parameter in any group with comparable CVI between individuals (p = .22).

CONCLUSIONS

CVI for TT4 and TT3 was halved in older compared to younger adults with two tests of TT4 needed to describe the individual set-point. Similar CVI between older adults caused TT4 to provide a reliable estimate of thyroid function, and the added value of measuring thyroxine could improve clinical practice.

Natural history of subclinical hypothyroidism and prognostic factors for the development of overt hypothyroidism: Tehran Thyroid Study (TTS)

OBJECTIVE

The significance of subclinical hypothyroidism (SCH) is largely due to its potential risk for developing overt hypothyroidism (OH). Investigations are still exploring predictive factors contributing to the progression of SCH to OH, particularly in patients with mildly elevated serum thyrotropin (TSH). We aimed to clarify the natural history of SCH and the predictive factors of its progression, based on the grade of SCH severity.

METHODS

This study was conducted within the framework of the Tehran Thyroid Study (TTS), in which 5783 individuals aged ≥ 20 years were followed. After applying exclusion criteria, data of 270 SCH subjects remained for the analysis. Thyroid function tests were assessed at baseline and every 3 years.

RESULTS

Of 270 participants with SCH, 239 (88.5%) had TSH level between 5.06 and 10 mU/L, and 31 (11.4%) had TSH ≥ 10 mU/L. During a median follow-up of 10 years, 40% had TSH within the reference range, 44% maintained elevated TSH, and 16% had added low T4 to the elevated TSH. The annual incidence rate of progression to OH was 22.3 (16.5-101.9) per 1000 person-years [18 (12.6-25.6) for those with TSH 5.07-9.9 mU/L and 57.8 (22.8-101.9) for patients with TSH ≥ 10 mU/L per 1000 person-years (P = 0.001)]. After adjusting age, sex, body mass index (BMI), thyroid peroxidase antibody (TPOAb), and serum TSH, only TPOAb positivity (HR: 2.31; 95% CI 1.10-4.83, P = 0.026) and baseline TSH level ≥ 10 mU/L (HR: 5.14; 95% CI 2.14-12.3, P < 0.001) remained as predictors for development of OH. In patients with TSH 5.07-9.9 mU/L, TPOAb positivity was associated with an increased risk of OH (HR: 2.41; 95% CI 1.10-5.30, P = 0.027). However, in patients with TSH ≥ 10 mU/L, TPOAb positivity was not a predictor (P = 0.49).

CONCLUSION

TPOAb and not TSH are associated with the development of OH in individuals with serum TSH below 10 mU/L, and follow-up at regular intervals is recommended in TPOAb-positive individuals with TSH between 5 and 10 mU/L.

Thyroid diseases in patients with active endogenous Cushing’s syndrome

Objective: Data about the impact of Cushing’s syndrome (CS) on thyroid is scarce. We aimed to identify the prevalence of thyroid diseases in patients with CS. Patients and Methods: Nineteen patients with CS and 40 healthy participants were included in the study. All patients were tested for free tri-iodothyronine (fT3), free thyroxine (fT4), thyroid-stimulating hormone (TSH), anti-thyroglobulin (anti-Tg), and antithyroid peroxidase (anti-TPO) levels, and thyroid ultrasonography (US). Results: Overt hypothyroidism, subclinical hypothyroidism, and subclinical hyperthyroidism was evident in 5.3%, 5.3%, and 21.1% of patients with CS; and 2.5%, 7.5%, and 15% of healthy subjects, respectively. fT3 and fT4 levels were lower in patients with CS. None of the patients with CS and 27.5% of the control group had autoimmune thyroid disease (AITD), which was demonstrated by both US findings and anti-TPO positivity (P=0.01). Frequency of thyroid nodule was 52.6% and 52.5% in patients with CS and controls, respectively (P=0.99). Conclusion: The prevalence of thyroid dysfunction, nodular thyroid disease, and goiter is comparable to healthy population. However, AITD is less prevalent among patients with CS. Although, hypercortisolism has an impact on hypothalamic-hypophyseal-thyroid axis, its clinical implication does not seem to be significant.

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 autoimmunity in Greenlandic Inuit

Objective

This study aimed to provide the first data on the occurrence of thyroid autoimmunity among Inuit in Greenland, a distinct ethnic group who is not iodine deficient.

Design

This study is a population-based cross-sectional study.

Methods

Data were collected in Nuuk in West Greenland and in Ammassalik district in East Greenland. Information on lifestyle, diet and diseases was obtained using questionnaires. Thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb) and thyroid-stimulating hormone (TSH) were measured in serum. Iodine and creatinine were measured in spot urine samples.

Results

The participation rate was 95% with 434 Inuit participants; 75% were smokers. Iodine excretion was 169 µg/24 h in urban West Greenland, 224 µg/24 h in the main town and 228 µg/24 h in settlements in rural East Greenland. TPOAb, TgAb or either of these was measured in the serum from 3.7, 5.9 and 8.3% of participants, respectively. TPOAb or TgAb was found in 9.3% of Inuit women and 7.5% of men and more frequently, in East Greenland Inuit with the higher iodine excretion (P = 0.02). There was some evidence suggesting that thyroid autoimmunity was more frequent among non-smokers (12.5%) compared to smokers (7.0%). Harbouring a thyroid autoantibody was most frequent in participants with TSH above 3.6 mIU/L (P < 0.001).

Conclusion

Thyroid autoantibodies were rare among Greenland Inuit. While iodine nutrition was associated with autoimmunity similarly to other ethnic groups, the influence of sex and smoking was limited. This could suggest genetic component in Inuit, but the impact of cold, selenium and persistent organic pollutants needs to be elucidated.

Obesity is associated with subclinical hypothyroidism in the presence of thyroid autoantibodies: a cross-sectional study

BACKGROUND

Both obesity and subclinical hypothyroidism (SCH) have adverse effects on human body, but the relationship between these two conditions remains inconsistent. The presence of thyroid autoantibodies influences thyroid hormone levels, and may further mediate the interaction between obesity and SCH. This study aimed to explore the association among obesity, SCH and thyroid autoantibodies.

METHODS

This study was a cross-sectional survey of 2505 subjects. Obesity was defined as a body mass index ≥28 kg/m². Serum concentrations of thyroid hormones, thyroid peroxidase antibody (TPO-Ab) and thyroglobulin antibody (Tg-Ab) were examined. Logistic analysis was used to explore the relation among obesity, SCH and thyroid autoantibodies.

RESULTS

A proportion of 11.54% (289/2505) subjects were obese, and 165 subjects had SCH. The positive rates of thyroid autoantibodies, TPO-Ab and Tg-Ab were 17.64% (442/2505), 11.02% (276/2505) and 14.13% (354/2505), respectively. The proportion of SCH was significantly higher in obese than nonobese subjects among those with positive thyroid autoantibodies [22.41% (13/58) vs. 11.72% (45/384), p = 0.025, χ2 test]. Moreover, obesity was significantly associated with SCH in the presence of thyroid autoantibodies after adjusting for confounding factors (OR 2.212, 95% CI 1.103 to 4.433, p = 0.025). A higher proportion of subjects with obesity had Tg-Ab positivity [17.99% (52/289) vs. 13.63% (302/2216), p = 0.045, χ2 test], and obesity remained significantly associated with Tg-Ab positivity by multiple logistic analysis (OR 1.504, 95% CI 1.077 to 2.101, p = 0.017).

CONCLUSIONS

Obesity was associated with SCH in the presence of thyroid autoantibodies. Examination of SCH is recommended in obese subjects with thyroid autoantibody positivity.

Assessment of iodine fortification of salt in the Danish population

PURPOSE

We assessed the effect of the current iodine fortification level (20 µg/g household salt and salt included in bread and bakery products) on inadequate and excessive intake in the general Danish population. Intake models with/without the contribution from food supplements and effects of excluding specific food groups were evaluated.

METHOD

Data from the Danish National Survey of Dietary Habits and Physical Activity in 2011-13 (N = 3946, aged 4-75 years) stratified by age-group and sex were used to estimate habitual dietary iodine intakes, and compared with established dietary reference values.

RESULTS

The proportion with an estimated inadequate iodine intake was ≤ 3% for males and ≤ 5% for females, except for 15-17-year-old girls, where the probable prevalence of an inadequate intake was 11%. Including the contribution from food supplements gave similar results (10%). High intakes (as defined by 95th percentile) from food sources generally did not exceed the tolerable upper intake level (UL). However, for the youngest age-groups (4-6-year-old boys/girls and 7-10-year-old boys), the 95th percentiles exceeded the UL with 11%, 4% and 7%, respectively, when food supplements were included in the estimates. Especially exclusion of dairy products and bread led to an inadequate intake for both boys and girls.

CONCLUSION

The current fortification level may provide an inadequate iodine intake for some females and on the other hand lead to excessive intakes in the youngest age-groups. The study shows the importance of choosing iodine-rich alternatives when excluding major sources of iodine in the Danish diet.

[Epidemiology of benign thyroid disorders in the adult population of the Republic of Belarus: analysis of nationwide statistics 2009 to 2019]

BACKGROUND

Nowadays, the Republic of Belarus belongs to the countries with sufficient iodine supply, which made it possible to reduce the incidence of non-toxic goiter and congenital hypothyroidism. However, even a slight change in iodine consumption influences the pattern of thyroid diseases. In addition to iodine deficiency, other environmental conditions, as well as genetic factors, play a significant role in the etiology of thyroid diseases.

AIM

To analyze the dynamics of the main epidemiological indicators of benign thyroid diseases from 2009 to 2019 in the adult population of the Republic of Belarus, using the data of official state statistics.

MATERIALS AND METHODS

The indicators of the incidence and prevalence of benign thyroid diseases were studied on the basis of state statistics for 2009-2019. To analyze the dynamics of the studied indicators, regression analysis was used with the construction of linear and polynomial models.

RESULTS

A decrease in the incidence and prevalence of diffuse euthyroid goiter and an increase in the incidence and prevalence of nodular euthyroid goiter, thyroiditis, acquired hypothyroidism, Graves' disease, as well as the incidence of nodular toxic goiter were revealed.

CONCLUSION

Obtained data indicate, that there is an increase in the prevalence of most of the studied thyroid diseases, despite the adequate iodine supply. The above justifies the need for further study of the causes of the identified trends, as well as the necessity of developing new methods of diagnosis and treatment of thyroid diseases.

Raised mortality in old adults with a history of hyperthyroidism following iodine fortification

OBJECTIVE

A transient rise in the occurrence of hyperthyroidism ensued the introduction of iodine fortification (IF) of salt in Denmark. Older adults are at risk of complications to hyperthyroidism that could prove fatal to vulnerable individuals. We evaluated the association between thyroid function and mortality in older adults before and after nationwide implementation of IF.

DESIGN

Retrospective cohort study.

PATIENTS

All 68-year-olds from the general population in the city of Randers were invited to participate in a clinical study in 1988 and followed until death, emigration or end of study (31 December 2017) using Danish registries.

MEASUREMENTS

Baseline measures comprised of a questionnaire, physical examination and blood and urine samples. Kaplan-Meier survival curves and Cox regression were used to determine the association between thyroid function and death before and after IF. Time-stratification of results before and after IF was employed due to violation of proportional hazards assumptions in Cox regression.

RESULTS

Median urinary iodine concentration was 42 µg/L at baseline consistent with moderate iodine deficiency. Hyperthyroidism (thyrotropin < 0.4 mIU/L) occurred in 37 (9.1%) participants. Kaplan-Meier survival curves showed an increase in mortality among participants with hyperthyroidism after IF. There was no significant association between hyperthyroidism and mortality before IF compared to euthyroid participants, but after IF hyperthyroid subjects had an increased mortality (adjusted hazard ratio: 2.22, 95% confidence interval: 1.44-3.44).

CONCLUSIONS

IF was associated with raised mortality among older adults with a history of hyperthyroidism and moderate iodine deficiency. Our results highlight the need for cautious iodine supplementation and for monitoring of IF.

Thyroid function disorders

Thyroid function disorders are the most common endocrine disorders in humans. They are frequently diagnosed, with prevalence varying between 2 and 6%, and a female to male ratio of up to 10:1. Disorders of thyroid function in the narrower sense are presented by its hyperactivity or underactivity, although there are conditions that lead to an increased concentration of thyroid hormones, without its increased activity. In iodine-sufficient regions, the most common cause of hyperthyroidism, as well as hypothyroidism, is an autoimmune disease of the thyroid. For hyperthyroidism, it is Graves' disease, with typical symptoms and signs of hypermetabolism. The diagnosis of hyperthyroidism is based on suppressed TSH and elevated fT4 (free, and in the differential diagnosis, elevated TSH-receptor-antibodies are crucial for Graves' disease. Management of Graves' disease relies on three equally potent approaches: medical therapy, ablative treatments with 131I-radiotherapy-RAI, and thyroidectomy. Hashimoto's thyroiditis is the most common cause of hypothyroidism in iodine-sufficient regions. Symptoms and signs of hypothyroidism are non-specific and correspond to the symptoms and signs of hypometabolism. The diagnosis is made based on elevated TSH with decreased fT4. Thyroxine-peroxidaseantibodies and thyroglobuline-antibodies are important in differential diagnosis. Sometimes elevated TRAb is found in Hashimoto's thyroiditis. The treatment of hypothyroidism is levothyroxine replacement therapy.

The role of seaweed as a potential dietary supplementation for enteric methane mitigation in ruminants: Challenges and opportunities

Seaweeds are macroalgae, which can be of many different morphologies, sizes, colors, and chemical profiles. They include brown, red, and green seaweeds. Brown seaweeds have been more investigated and exploited in comparison to other seaweed types for their use in animal feeding studies due to their large sizes and ease of harvesting. Recent in vitro and in vivo studies suggest that plant secondary compound-containing seaweeds (e.g., halogenated compounds, phlorotannins, etc.) have the potential to mitigate enteric methane (CH4) emissions from ruminants when added to the diets of beef and dairy cattle. Red seaweeds including Asparagopsis spp. are rich in crude protein and halogenated compounds compared to brown and green seaweeds. When halogenated-containing red seaweeds are used as the active ingredient in ruminant diets, bromoform concentration can be used as an indicator of anti-methanogenic properties. Phlorotannin-containing brown seaweed has also the potential to decrease CH4 production. However, numerous studies examined the possible anti-methanogenic effects of marine seaweeds with inconsistent results. This work reviews existing data associated with seaweeds and in vitro and in vivo rumen fermentation, animal performance, and enteric CH4 emissions in ruminants. Increased understanding of the seaweed supplementation related to rumen fermentation and its effect on animal performance and CH4 emissions in ruminants may lead to novel strategies aimed at reducing greenhouse gas emissions while improving animal productivity.

Adaptation to a High Iodine Intake in Greenland Inuit Suggested by Thyroid Disease Pattern

Objective: Arctic living is influenced by cold winters, short summers, and excessive iodine intake from the traditional Inuit diet providing for habitation of the Arctic for centuries. This is changing and we surveyed thyroid function in populations living in Greenland. Design: Population-based cross-sectional study. Methods: Data were collected in the capital city in West Greenland and in rural East Greenland. Information on lifestyle, dietary habits, and medical history was obtained using questionnaires. Thyrotropin, free thyroxine, free triiodothyronine, thyroglobulin, and thyroglobulin antibody were measured in serum, iodine, and creatinine in spot urine samples. Results: One percent of the Greenlandic population was invited and 535 participated with an overall participation rate of 95%. Iodine excretion was 225 μg/24 hours in East Greenland and 169 μg/24 hours among West Greenland Inuit. Hyperthyroidism occurred in 10.7% of West Greenlandic Inuit (men/women: 4.3%/16.3%) and 7.8% of East Greenlandic Inuit (3.8%/12.8%). Hypothyroidism was found in 2.7% in West Greenland (0.0%/5.0%) and 5.6% (5.6%/5.6%) in East Greenland. Conclusion: Hyperthyroidism was frequent among Inuit and the occurrence of hypothyroidism was low. The pattern of hyper- and hypothyroidism among Greenlandic Inuit with adequate iodine intake was comparable with those seen in populations with iodine deficiency. Inuit may thus have adapted to excessive iodine intake over centuries, causing a need for a higher iodine intake to prevent iodine deficiency disorders.

Incidence of thyroid diseases: Results from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

OBJECTIVE

To evaluate incidence of subclinical and overt hyperthyroidism and hypothyroidism.

METHODS

The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) is a prospective cohort study of 15,105 civil servants, examined at baseline and over a 4-year follow-up. This analysis included 9,705 participants with normal thyroid function at baseline, follow-up information about thyroid function and with no report of using drugs that may interfere in the thyroid function. Thyroid function was defined by TSH/FT4 levels or routine use of thyroid hormones/anti-thyroid medications. Annual and cumulative (over 4-year) incidence rates were presented as percentages (95% Confidence Intervals).

RESULTS

The incidence of all overt and subclinical thyroid disease was 6.7% (1.73%/year): 0.19% for overt hyperthyroidism (0.048%/year), 0.54% for subclinical hyperthyroidism (0.14%/year), 1.98% for overt hypothyroidism (0.51%/year), and 3.99% for subclinical hypothyroidism (1.03%/year). The incidence of all thyroid diseases was higher in women, when compared to men, with a low women:men ratio (1.36). For Blacks the highest incidence was for overt hyperthyroidism, while for Whites, the highest incidence was for overt hypothyroidism. However, the highest incidence of overt hyperthyroidism was detected in Asian descendants. The presence of antithyroperoxidase antibodies at baseline was associated with higher incidence of overt thyroid diseases.

CONCLUSION

These results showed a high incidence of hypothyroidism, which is compatible with a country with a more-than-adequate iodine intake. The low women:men ratio of the incidence of thyroid dysfunction highlights the importance of the diagnosis of thyroid diseases among men in Brazil.

Iodine nutrition optimization: are there risks for thyroid autoimmunity?

Iodine deficiency is still the main cause of preventable thyroid disorders, worldwide. To optimize iodine intake, programs of voluntary or mandatory iodization of salt have been implemented in several iodine-deficient countries and iodine sufficiency has been achieved in many. Despite the clear beneficial effects on thyroid health, some concerns have been raised on the presumed detriment of iodine prophylaxis on thyroid autoimmunity. Very recent studies aimed at evaluating the long-term consequences of iodine supplementation on thyroid autoimmunity and related dysfunction, have clearly demonstrated that the early post-iodization increase in thyroid antibody positivity is largely transient and not clinically relevant, since the prevalence of overt thyroid dysfunction has remained reassuring low over two decades. The recommended iodine intake is therefore safe with regard to thyroid autoimmunity, the benefits largely outweighing the risks in a population with a stable median iodine concentration not exceeding 300 μg/L. Thus, a possible increase in thyroid autoimmunity should not represent a limitation to promoting iodine supplementation in the general population, also taking into account the steady rise in prevalence of autoimmune disorders which has occurred in the last few decades because of environmental factors other than iodine.

Thyroid Autoimmunity and Dysfunction in Sri Lankan Children and Adolescents After 22 Years of Sustained Universal Salt Iodization

Background: Sri Lanka introduced universal salt iodization (USI) in 1995 after which we demonstrated a high thyroglobulin antibody (TgAb) prevalence in 1998. However, it is unclear whether thyroid autoimmunity persists in the long term in populations exposed to sustained USI and whether such populations have an excess of thyroid dysfunction. We evaluated the prevalence of thyroid autoantibodies and dysfunction in Sri Lankan children and adolescents after more than two decades of sustained USI. Methods: We selected 10- to 18-year-old subjects of both sexes (randomized cluster sampling) from all 9 provinces of Sri Lanka in this cross-sectional study. Blood, urine, and anthropometric data were collected and thyroid ultrasound scans were performed. Validated statistical methods were used to derive local population-specific reference ranges for all thyroid parameters. We also measured urine iodine concentration (UIC), salt, and water iodine concentrations. Results: Blood and urine samples from 2507 and 2473 subjects respectively, and ultrasound scans from 882 subjects were analyzed. Population-derived upper limits for thyroid peroxidase antibody (TPOAb) and TgAb, and reference ranges for triiodothyronine, thyroxine, and thyrotropin (total and age-year-related groups) were significantly different from manufacturer's reference ranges. Using these derived ranges, the prevalence of TPOAb was 10.3% and TgAb was 6.4%. Of the TPOAb-positive subjects, TPOAb were of low concentration in 66.2% (1-3 times the upper limit of the reference range [ULRR]) and showed the strongest association with subclinical hypothyroidism (SCH) at the highest concentrations (>4 ULRR). The prevalence of SCH was 3%. Median UIC (interquartile range) was 138.5 μg/L (79.4-219.0) with regional variability, and median thyroglobulin was 8.3 ng/mL (4.1-13.5). Goiter prevalence was 0.6% and 1.93% (thyroid volume compared to age and body surface area, respectively). Salt and water iodine concentrations were satisfactory. Conclusions: Sri Lanka has safely and effectively implemented USI with good sources of iodine, leading to sustained iodine sufficiency over more than two decades. The early postiodization TgAb surge (42.1%) has settled (6.4%), and despite a persistently high TPOAb prevalence (10.3%), SCH prevalence remains low (3%). Further studies should be undertaken to monitor thyroid autoimmune dysfunction in Sri Lankan children, using age-specific, population-derived reference ranges.

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.

Spatial clustering and meso-scale correlates of thyroid disorder among women in India: evidence from the National Family Health Survey (2015–16)

Purpose

Thyroid disorders are a major public health burden. Generally, women exhibit higher differentials in the prevalence of these disorders. This study focuses on the socio-economic and behavioural correlates of thyroid disorders along with their spatial clustering among women of reproductive age in India.

Methods

The study uses dataset from the fourth National Family Health Survey (NFHS-4) carried out in 2015–16 to assess self-reported thyroid disorders. Poor–rich ratio (PRR) and concentration index (CI) were used to study the variation in thyroid disorder among women arising out of economic inequality. Moran’s I statistics and bivariate local spatial autocorrelation (BiLISA) maps were used to understand spatial dependence and clustering of thyroid disorder. Spatial lag and error models were applied to examine the correlates of the disorder.

Results

Thyroid disorder prevalence was higher among women from socio-economically better-off households. Adjusted effects showed that users of iodized salt were 1.14 times more likely to suffer from a thyroid disorder as compared to non-users, which is contrary to the general belief that a higher percentage of consumption of iodide salt leads to a lower prevalence of thyroid disorder. A higher autoregressive coefficient (0.71) indicated significantly higher spatial clustering in thyroid disorders.

Conclusions

The prevalence of thyroid disorder in India depends appreciably on spatial and various ecological factors. Sedentary lifestyles among women may be aggravating diseases, which has strong linkage with thyroid disorders. It is strongly recommended to effectively integrate universal salt iodization with activities geared towards the elimination of iodine deficiency disorders.

Iodoprophylaxis and thyroid autoimmunity: an update

Adequate iodine intake is necessary for normal thyroid function. Iodine deficiency is associated with serious complications, but also iodine excess can lead to thyroid dysfunction, and iodine supplementation aimed to prevent iodine deficiency disorders has been associated with development of thyroid autoimmunity. The epidemiology of thyroid diseases has undergone profound changes since the implementation of iodoprophylaxis, notably by means of iodine-enriched salt, specifically resulting in decreased prevalence of goiter and neonatal hypothyroidism, improved cognitive function development in infancy, and reduced incidence of more aggressive forms of thyroid cancer. The main question we address with this review is the clinical relevance of the possible effect on autoimmunity exerted by the use of iodine-enriched salt to correct iodine deficiency. In animal models, exogenous iodine is able to trigger or exacerbate thyroid autoimmunity, but it is still not clear whether the observed immunological changes are due to a direct effect of iodine on immune response, or whether they represent a secondary response to a toxic effect of iodine on thyroid tissue. Previous iodine status of a population seems to influence the functional thyroid response to increased iodine intake and possibly the development of thyroid autoimmunity. Moreover, the prevalence of thyroid antibodies, regarded as hallmark of autoimmune thyroid disease, varies between populations under the influence of genetic and environmental factors, and the presence of thyroid antibodies does not always coincide with the presence of thyroid disease or its future development. In addition, the incidence of autoimmune diseases shows a general increasing trend in the last decades. For all these reasons, available data are quite heterogeneous and difficult to analyze and compare. In conclusion, available data from long-term population surveys show that a higher than adequate population iodine intake due to a poorly controlled program of iodine prophylaxis could induce thyroid dysfunction, including thyroid autoimmunity mostly represented by euthyroid or subclinical hypothyroid autoimmune thyroiditis. Close monitoring iodine prophylaxis is therefore advised to ensure that effects of both iodine deficiency and iodine excess are avoided.

Determination of age and sex specific TSH and FT4 reference limits in overweight and obese individuals in an iodine-replete region: Tehran Thyroid Study (TTS)

Introduction: To determine age and sex-specific thyrotropin (TSH) and free thyroxine (FT4) reference ranges according to body mass index (BMI) categories. Methods: With regards to the National Academy of Clinical Biochemistry (NACB) criteria, a total of 2818 individuals from the Tehran Thyroid Study population was selected and categorized in three BMI groups. Results: TSH levels did not differ significantly between BMI groups (p = .054). Females had statistically higher TSH levels than males in all BMI categories (p < .001). According to age-specific analyses, the youngest category (20-29 years) had the highest median values of serum TSH in all BMI groups. With increasing BMI, the 2.5^th percentile of TSH remained approximately unchanged and the 97.5^th percentile showed an increasing pattern. FT4 level was significantly higher in the normal weight group compared to obese individuals (p < .001); females had significantly lower FT4 levels than males in normal weight and obese groups (p < .001). According to age categories, the youngest group (20-29 years) had higher levels of FT4 than the elderly group in all BMI categories. A decreasing pattern in both 2.5^th and 97.5^th percentiles of FT4 was observed along with increasing BMI. Conclusions: Compared to the normal weight population, obese individuals have slightly lower FT4 concentrations accompanied by similar TSH levels. With increasing BMI, upper limits of TSH and FT4 show increasing and decreasing patterns, respectively.

Thiocyanate in excess develops goiter followed by auto immune thyroid diseases even after effective salt iodization in a rural community of north east India

PURPOSE

Salt iodization in Manipur of north-east India failed to prevent endemic goiter, therefore an in depth study carried out to evaluate thyroid functions of goitrous subjects in a randomly selected region.

METHODS

Goiter survey conducted in children and women of reproductive ages by palpation followed by measurement of urinary iodine, thiocyanate and house-hold salt iodine to evaluate iodine nutritional status and consumption pattern of bamboo-shoots (BS). In all grade-2 goitrous subjects, free thyroxine, triiodothyronine, TSH, TPO and Tg antibodies, thyroid volume and echogenecity by ultrasonography and cytomorphology of thyroid by FNAC studied.

RESULTS

Study population was 2486 children and 1506 women, goiter prevalence was 12.59% and 16.27% respectively; median urinary iodine and mean thiocyanate were 166 µg/l and 0.729 ± 0.408 mg/dl while salt iodine was ≥30 ppm. Serum thyroid hormones and TSH profiles of all grade-2 goitrous subjects showed 16.21% were subclinically hypothyroid, 2.16% overt hypothyroid, 4.86% subclinically hyperthyroid and 6.48% overt hyperthyroid, serum TPO- and Tg-antibodies found positive in 41.62%. Ultrasonographic results showed 24% had enlarged thyroid and 86.4% hypoechoic. Cytomorphological studies showed prevalence of colloid goiter (41.08%), lymphocytic thyroiditis (37.83%), Hashimoto's thyroiditis (8.10%), autoimmune thyroiditis (4.32%), sub-acute thyroiditis (2.16%) and 1.62% each papillary, medullary carcinoma, simple diffused hyperplasia and adenomoid nodular goiter.

CONCLUSIONS

Grade-2 goitrous individuals in this mild goiter endemic region were affected by hypo- and hyperthyroidism with hypoechoic thyroid and thyroiditis. Thiocyanate that originates from BS even in presence of adequate iodine developed goiter and led goitrous population towards such diseases.

Association of breastfeeding with thyroid function and autoimmunity in postmenopausal women

OBJECTIVE

Whether breastfeeding influences thyroid function and autoimmunity is not elucidated. We examined the association of history of breastfeeding with thyroid hormones and thyroperoxidase antibody (TPOAb).

DESIGN

Cross-sectional study of data from the 2013-2015 Korea National Health and Nutrition Examination Survey.

METHODS

A total of 816 postmenopausal women were stratified into three groups according to the duration of breastfeeding and number of breastfed children. Thyroid hormones levels, TPOAb titers, and the prevalence of hypothyroidism and TPOAb positivity were evaluated in each group.

RESULTS

Subjects with a history of prolonged breastfeeding had lower levels of thyrotropin (TSH) and TPOAb than the others. After adjusting for multiple confounding factors, the estimated means of TSH and TPOAb were associated with cumulative duration of breastfeeding. Duration of breastfeeding per child was associated with TSH levels, and number of breastfed children was associated with TPOAb titers. The odds ratio (OR) of hypothyroidism was significantly lower in group for ≥36 months of cumulative duration of breastfeeding, and the OR of TPOAb positivity was significantly lower in group with ≥3 breastfed children. In addition, duration of breastfeeding and the number of breastfed children were linearly correlated with log TSH and TPOAb each other in the multivariate model.

CONCLUSIONS

The present study showed that prolonged breastfeeding was inversely associated with TSH and the prevalence of hypothyroidism. Moreover, TPOAb and the prevalence of TPOAb positivity were inversely associated with number of breastfed children. These results indicate that breastfeeding may exert a protective effect on thyroid function and autoimmunity.

Subclinical Thyroid Dysfunction and the Risk of Cardiovascular Disease

The prevalence of subclinical hypothyroidism (SH) is 3-10%. The prevalence of subclinical hyperthyroidism (SHr) is 0.7-9.7%. Thyroid hormones affect cardiac electrophysiology, contractility, and vasculature. SH is associated with an increased risk of coronary heart disease (CHD), especially in subjects under 65. SHr seems to be associated with a slightly increased risk of CHD and an increase in CHD-related mortality. Both SH and SHr carry an increased risk of developing heart failure (HF), especially in those under 65. Both SH and SHr are associated with worse prognoses in patients with existing HF. SH is probably not associated with atrial fibrillation (AF). SHr, low normal thyroid-stimulating hormone (TSH) and high normal free thyroxine (FT4) are all associated with the increased risk of AF. An association between endothelial dysfunction and SH seems to exist. Data regarding the influence of SHr on the peripheral vascular system are conflicting. SH is a risk factor for stroke in subjects under 65. SHr does not increase the risk of stroke. Both SH and SHr have an unfavourable effect on cardiovascular disease (CVD) and all-cause mortality. There is a U-shaped curve of mortality in relation to TSH concentrations. A major factor that modifies the relation between subclinical thyroid disease (SCTD) and mortality is age. SH increases blood pressure (BP). SHr has no significant effect on BP. Lipids are increased in patients with SH. In SHr, high-density lipoprotein cholesterol and lipoprotein( a) are increased. SCTD should be treated when TSH is over 10 mU/l or under 0.1 mU/l. Treatment indications are less clear when TSH is between normal limits and 0.1 or 10 mU/L. The current state of knowledge supports the understanding of SCTD's role as a risk factor for CVD development. Age is a significant confounding factor, probably due to age-associated changes in the TSH reference levels.

Lean-seafood intake increases urinary iodine concentrations and plasma selenium levels: a randomized controlled trial with crossover design

PURPOSE

Iodine deficiency due to insufficient nutritional intake is a public health challenge in several European countries, including Norway. Lean-seafood has a high iodine and arsenic (As) content and is a good source of selenium (Se). Evidence of a direct effect of increased intake of lean-seafood on iodine status is limited. The main aims were to determine the iodine status at baseline and to investigate possible dietary effects on urinary iodine concentration (UIC) after intervention with lean-seafood versus non-seafood. Plasma Se, and plasma and urinary As concentrations were also measured.

METHODS

A randomized controlled crossover study comprising two 4 weeks experimental periods with two balanced diets varied in main proteins (60% of total dietary proteins) of lean-seafood and non-seafood, separated by a 5 week washout period.

RESULTS

Twenty participants (7 males, 13 females) were included and the mean ± SD age was 50.6 ± 15.3 years for all participants. Fasting UIC was median (25th, 75th percentile) 70 (38, 110) and 79 (49, 94) µg/L in the lean-seafood and non-seafood intervention at baseline, respectively. UIC increased after 4 weeks of the lean-seafood intervention to 135 (110, 278) µg/L, but not after the non-seafood intervention [58 (33, 91) µg/L] (P diet-effect < 0.001). Fasting plasma Se increased in the lean-seafood intervention and decreased in the non-seafood intervention (P diet-effect = 0.001). Fasting urinary and plasma As increased in the lean-seafood intervention and was unchanged in the non-seafood intervention (P diet-effect < 0.001).

CONCLUSION

The participant's UIC was below the recommended median (100 µg/L) at baseline, but increased sufficiently after a 4 week intervention with lean-seafood.

Protective role of selenium on thyroid morphology in iodine-induced autoimmune thyroiditis in Wistar rats

Excess iodine may induce and exacerbate autoimmune thyroiditis (AIT) in humans and animals. In order to assess the potential protective mechanisms of selenium (Se) in thyroid autoimmunity, the effects of inorganic Se (sodium selenite) administration on thyroid morphology and follicular cytology were investigated in adult Wistar rats with iodine-induced AIT. A total of 48 adult Wistar rats (24 females, 24 males) were allocated to one of four dietary regimens: C0, control; C1, only potassium iodine (KI); C2, concomitant KI and Se; C3, only KI initially, followed by Se administration. For AIT induction the rats were fed with 0.05% KI for 56 days. Se-treated rats received 0.3 mg/l sodium selenite in drinking water. Thyroid tissues were collected for pathologic diagnosis after 7 days in C0 group, 56 days in C1 and C2 groups, and 112 days in C3 group. In C1 group, moderate to severe thyroiditis was observed in 83% of males and 50% of female rats (P=0.223). In C3 group 16.7% of male rats developed moderate thyroiditis and none in C2 group, whereas no females were identified with moderate to severe thyroiditis in C2 or C3 group. Thus, the administration of Se was proven to have protective effects against thyroiditis cytology in both male and female Wistar rats.

Sex differences in subclinical hypothyroidism and associations with metabolic risk factors: a health examination-based study in mainland China

BACKGROUND

The association between subclinical hypothyroidism (SCH) and metabolic risk factors in the general health examination-based population has been widely explored. However, the results have been inconclusive. Additionally, the sex differences in the prevalence of SCH and the association of SCH with metabolic risk factors remain unknown.

METHODS

We conducted this cross-sectional study using data from health examination-based participants between June 2016 and April 2018 in our health examination centre. Sex differences SCH and the association of SCH with metabolic risk factors were explored.

RESULTS

The total prevalence of SCH was 3.40% among the 5319 included participants, and 4.90% among the 2306 female participants, which was much higher than the prevalence of 2.26% among the 3013 male participants (p < 0.05). In males, the difference between participants younger than 60 and aged 60 or older was not significant (p = 0.104); while in females, the difference between participants younger than 40 and participants aged 40 or older was statistically significant (p = 0.023). Multivariate logistic regression analysis demonstrated that age (OR = 0.568, p = 0.004), body-mass index (BMI) (OR = 5.029, p < 0.001) and systolic/diastolic blood pressure (SBP/DBP) (OR = 5.243, p < 0.001) were independent predictors of SCH in females, but no metabolic risk factor was significantly associated with SCH in males. Further analysis revealed that the prevalence was much higher in participants with one or two metabolic risk factors than in those with no above metabolic risk factors regardless of age (p < 0.01).

CONCLUSIONS

Our study demonstrates that high BMI and/or high blood pressure are associated with SCH in female participants, and the prevalence of SCH among women with one or two metabolic risk factors ranges from 7.69-14.81%, which indicates that in such a population, serum concentrations of TSH and FT4 may be routinely screened in mainland China. Certainly, prospective, large-scale studies with long follow-up period are still necessary to further verify our results.

The interplay between thyroid and liver: implications for clinical practice

A complex relationship exists between thyroid and liver in health and disease. Liver plays an essential physiological role in thyroid hormone activation and inactivation, transport, and metabolism. Conversely, thyroid hormones affect activities of hepatocytes and hepatic metabolism. Serum liver enzyme abnormalities observed in hypothyroidism may be related to impaired lipid metabolism, hepatic steatosis or hypothyroidism-induced myopathy. Severe hypothyroidism may have biochemical and clinical features, such as hyperammonemia and ascites, mimicking those of liver failure. Liver function tests are frequently abnormal also in hyperthyroidism, due to oxidative stress, cholestasis, or enhanced osteoblastic activity. Antithyroid drug-associated hepatotoxicity is a rare event, likely related mainly to an idiosyncratic mechanism, ranging from a mild hepatocellular damage to liver failure. Propylthiouracil-induced liver damage is usually more severe than that caused by methimazole. On the other hand, thyroid abnormalities can be found in liver diseases, such as chronic hepatitis C, liver cirrhosis, hepatocellular carcinoma, and cholangiocarcinoma. In particular, autoimmune thyroid diseases are frequently found in patients with hepatitis C virus infection. These patients, especially if thyroid autoimmunity preexists, are at risk of hypothyroidism or, less frequently, thyrotoxicosis, during and after treatment with interpheron-alpha alone or in combination with ribavirin, commonly used before the introduction of new antiviral drugs. The present review summarizes both liver abnormalities related to thyroid disorders and their treatment, and thyroid abnormalities related to liver diseases and their treatment.

[The thyroid gland in old age : Physiology and pathology]

In healthy older people the metabolism of thyroid hormones is physiologically altered and can possibly even actively contribute to longevity. This should also be taken into consideration in the treatment of diseases of the thyroid and principally also for younger patients. For example, with progressing age comorbidities become more prevalent and especially in cardiovascular diseases, hyperthyroidism is less well tolerated, and should be treated more aggressively. Benign multinodular goiter also becomes more prevalent in old age and should be surgically treated when causing mechanical symptoms. The treatment concept for malignant diseases should be adapted to the holistic situation of the patient but principally in the same manner as in younger patients. Old and very old patients also benefit from adequate, risk-adapted treatment of thyroid gland diseases so that appropriate diagnostics and clarification are meaningful, regardless of age.

Association of Hypothyroidism and Mortality in the Elderly Population: A Systematic Review and Meta-Analysis

CONTEXT

The evidence of whether hypothyroidism increases mortality in the elderly population is currently inconsistent and conflicting.

OBJECTIVE

The objective of this meta-analysis is to determine the impact of hypothyroidism on mortality in the elderly population.

DATA SOURCES

PubMed, Embase, Cochrane Library, Scopus, and Web of Science databases were searched from inception until May 10, 2019.

STUDY SELECTION

Studies evaluating the association between hypothyroidism and all-cause and/or cardiovascular mortality in the elderly population (ages ≥ 60 years) were eligible.

DATA EXTRACTION

Two reviewers independently extracted data and assessed the quality of the studies. Relative risk (RR) was retrieved for synthesis. A random-effects model for meta-analyses was used.

DATA SYNTHESIS

A total of 27 cohort studies with 1 114 638 participants met the inclusion criteria. Overall, patients with hypothyroidism experienced a higher risk of all-cause mortality than those with euthyroidism (pooled RR = 1.26, 95% CI: 1.15-1.37); meanwhile, no significant difference in cardiovascular mortality was found between patients with hypothyroidism and those with euthyroidism (pooled RR = 1.10, 95% CI: 0.84-1.43). Subgroup analyses revealed that overt hypothyroidism (pooled RR = 1.10, 95% CI: 1.01-1.20) rather than subclinical hypothyroidism (pooled RR = 1.14, 95% CI: 0.92-1.41) was associated with increased all-cause mortality. The heterogeneity primarily originated from different study designs (prospective and retrospective) and geographic locations (Europe, North America, Asia, and Oceania).

CONCLUSIONS

Based on the current evidence, hypothyroidism is significantly associated with increased all-cause mortality instead of cardiovascular mortality among the elderly. We observed considerable heterogeneity, so caution is needed when interpreting the results. Further prospective, large-scale, high-quality studies are warranted to confirm these findings.

Autoimmune thyroid diseases after 25 years of universal salt iodisation: an epidemiological study of Chinese adults in areas with different water iodine levels

The present study aimed to evaluate the status of iodine nutrition and thyroid function in adults, to understand the distribution of thyroid disease in people with autoimmune thyroid disease (AITD) in different water iodine areas and to explore the relationship between serum iodine, urine iodine and thyroid function in people with AITD. A cross-sectional survey was conducted in areas of Shandong Province with different water iodine levels, and subsequently 1225 adults were enrolled from iodine-deficient (ID), iodine-adequate (IA) and iodine-excess (IE) areas. Urinary iodine, water iodine, salt iodine, serum iodine and thyroid function were measured. According to the urine iodine concentration, the ID and IA areas were defined as iodine sufficient and the IE area as iodine excessive. Urine iodine, serum iodine, free thyroxine (FT4) and thyroid-stimulating hormone (TSH) levels were comparatively higher in the IE area. The positive rate of thyroglobulin antibody (19·1 %) and the prevalence of AITD (21·8 %) were higher in the ID areas; the prevalence of subclinical hypothyroidism was lowest in the ID areas (7·3 %) and highest in the IE area (16·3 %). Among the AITD population, urinary iodine concentration, free triiodothyronine, FT4 and TSH had a non-linear correlation with serum iodine; abnormal TSH level, serum iodine concentration > 110 µg/l and goitre were risk factors for AITD in adults, especially females. Our data collectively suggest that universal salt iodisation has improved the iodine nutritional status of the population in ID areas in China. Non-step-by-step iodine fortification may induce the transformation of thyroid autoimmune diseases from recessive-to-dominant in susceptible people. Moreover, enhanced monitoring of thyroid function in people with AITD is important.

Long-term iodine nutrition is associated with longevity in older adults: a 20 years’ follow-up of the Randers–Skagen study

Iodine intake affects the occurrence of thyroid disorders. However, the association of iodine intake with longevity remains to be described. This led us to perform a 20 years’ follow-up on participants from the Randers–Skagen (RaSk) study. Residents in Randers born in 1920 (n 210) and Skagen born in 1918–1923 (n 218) were included in a clinical study in 1997–1998. Mean iodine content in drinking water was 2 µg/l in Randers and 139 µg/l in Skagen. We collected baseline data through questionnaires, performed physical examinations and measured iodine concentrations in spot urine samples. Income data were retrieved from Danish registries. We performed follow-up on mortality until 31 December 2017 using Danish registries. Complete follow-up data were available on 428 out of 430 of participants (99·5 %). At baseline, the median urinary iodine concentration was 55 µg/l in Randers and 160 µg/l in Skagen residents. Participants were long-term residents with 72·8 and 92·7 % residing for more than 25 years in Randers and Skagen, respectively. Cox regression showed that living in Skagen compared with Randers was associated with a lower hazard ratio (HR) of death in both age- and sex-adjusted analyses (HR 0·60, 95 % CI 0·41, 0·87, P = 0·006), but also after adjustment for age, sex, number of drugs, Charlson co-morbidity index, smoking, alcohol and income (HR 0·60, 95 % CI 0·41, 0·87, P = 0·008). Residing in iodine-replete Skagen was associated with increased longevity. This indicates that long-term residency in an iodine-replete environment may be associated with increased longevity compared with residency in an iodine-deficient environment.

Incidence of thyroid disorders in the second decade of adequate iodine supply in Slovenia

BACKGROUND

The incidence of thyroid disorders importantly depends on iodine supply and may change over time. There are only a few data available regarding the change in the incidence of thyroid disorders following the increase in iodine supply. Therefore, the aim of this study was to establish the incidence of thyroid disorders in the second decade of adequate iodine supply in Slovenia.

METHODS

The medical records of 17,828 adult patients who were examined at this department for the first time in the years 2011, 2012, 2013 and 2014 were reviewed. The incidence of diffuse and nodular goiter, thyroid autonomy, Graves' disease, non-hypothyroid and hypothyroid Hashimoto's thyroiditis in the stable catchment area of the University Medical Centre Ljubljana with 1,000,000 inhabitants was followed.

RESULTS

A significantly lower incidence of thyroid autonomy was observed in the year 2014 as compared to 2011 (p = 0.006), a significantly higher incidence of Hashimoto's thyroiditis in 2014 as compared to 2013 (p = 0.003), and a significantly higher incidence of non-hypothyroid Hashimoto's thyroiditis in 2014 as compared to 2011 and 2013 (p = 0.005 and p = 0.022, respectively). The incidence of other thyroid diseases did not change significantly in the observed period.

CONCLUSION

In the second decade of adequate iodine supply in Slovenia, we established a similar or even a lower incidence of most thyroid diseases in the observed 4 years with the exception of Hashimoto's thyroiditis.

No association between anti-thyroidperoxidase antibodies and bipolar disorder: a study in the Dutch Bipolar Cohort and a meta-analysis

BACKGROUND

Thyroid autoimmunity has been associated with bipolar disorder (BD). However, results from previous studies on the seroprevalence of anti-thyroid peroxidase antibodies (TPO-abs) in BD are inconsistent.

OBJECTIVES

The aim of the present study is to investigate whether the seroprevalence and titer levels of TPO-abs are related to BD.

METHOD

TPO-abs were measured in plasma samples of 760 patients with bipolar disorder, 261 first-degree relatives and 363 controls by enzyme-linked immunosorbent assay (ELISA). To address methodological limitations of previous studies, we assessed clinical characteristics with several (self-reported) questionnaires to investigate whether TPO-abs positivity is related to particular clinical subgroups of BD patients. We performed an additional meta-analysis of seroprevalences of TPO-abs in BD patients including data from present and previous studies.

RESULTS

Seroprevalence or titer levels of TPO-abs did not significantly differ between patients with BD, their first-degree relatives, and controls. In BD patients, the prevalence of TPO-abs was unrelated to specific clinical factors, including lithium use. Our meta-analysis of twelve studies showed an overall odds ratio of 1.3 (CI 95 %: 0.7-2.3; p = 0.30), reaffirming the absence of an association of BD with TPO-abs.

CONCLUSIONS

In the largest study of TPO-abs in BD to date, our findings indicate that TPO-abs are not associated with (the risk for) bipolar disorder.

Changes in subtypes of overt thyrotoxicosis and hypothyroidism following iodine fortification

OBJECTIVE

To investigate the impact of mandatory iodine fortification (IF) on the incidence of nosological subtypes of overt thyrotoxicosis and hypothyroidism.

DESIGN

We identified and scrutinized all possible new cases of overt thyrotoxicosis and hypothyroidism in an open cohort in Northern Jutland (n = 309 434; 1 January 1997) during the years 2014-2016. Individual medical history was evaluated to verify and detail the incidence of overt thyroid dysfunction and for classification into nosological subtypes. A number of cases were excluded during final verification due to spontaneous normalization of thyroid function, as they had no medical history suggesting a known condition, which could transiently affect thyroid function (subacute/silent thyroiditis, PPTD and iatrogenic thyroid dysfunction). An identical survey was conducted in 1997-2000 prior to mandatory IF of salt (13 µg/g) that was in effect from year 2001.

RESULTS

The standardized incidence rate (SIR) of verified overt thyrotoxicosis decreased markedly from 97.5/100 000/year in 1997-2000 to 48.8 in 2014-2016 (SIRR: 0.50 [95% CI: 0.45-0.56]). This was due to a distinct decrease in the SIR of multinodular toxic goitre (SIRR: 0.18 [0.15-0.23]), solitary toxic adenoma (SIRR: 0.26 [0.16-0.43]) and to a lesser degree Graves' disease (SIRR: 0.67 [0.56-0.79]). SIR for overt hypothyroidism was unaltered by 2014-2016 (SIRR: 1.03 [0.87-1.22]). However, age distribution shifted with more young and fewer elderly cases of verified overt hypothyroidism.

CONCLUSION

Mandatory IF caused a substantial reduction in SIR of verified overt thyrotoxicosis (especially of nodular origin) while avoiding an increase in SIR of verified overt hypothyroidism.

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).

Adverse effects on thyroid of Chinese children exposed to long-term iodine excess: optimal and safe Tolerable Upper Intake Levels of iodine for 7- to 14-y-old children

Background

The adverse effects of iodine excess on the thyroid in children are not well understood, and the Tolerable Upper Intake Level for iodine in children is unclear.

Objective

The aims of this study were to assess the effects of chronic long-term iodine excess on thyroid function in children and to explore the safe Tolerable Upper Intake Level of iodine in Chinese children.

Design

A multistage cross-sectional study was conducted in 2224 children from areas with adequate to excessive iodine content in drinking water. Repeated samples of 24-h urine and spot urine samples were collected to estimate habitual daily iodine intakes of children. The thyroid volume in children was measured and blood samples were collected to determine thyroid function.

Results

The habitual iodine intake of children was 298 μg/d (range: 186-437 μg/d). The total goiter rate was 9.7%, 232 (11.2%) children had hyperthyrotropinemia, and 232 (11.2%) children had thyroglobulin (Tg) concentrations >40 μg/L. The prevalence of hyperthyrotropinemia was >10% in children at iodine intakes of 200-300 μg/d. Tg concentrations increased with increased iodine intake (β = 0.5; 95% CI: 0.4, 0.6), and the prevalence of Tg >40 μg/L was >3% in all iodine-intake groups. Multivariate logistic regression analysis indicated that the risk of total goiter significantly increased at iodine intakes ≥250-299 μg/d in 7- to 10-y-old children (OR: 8.8; 95% CI: 2.3, 34.0) and at iodine intakes ≥300-399 μg/d in 11- to 14-y-old children (OR: 5.2; 95% CI: 1.5, 18.3). However, there were no consistent differences in the risk of hyperthyrotropinemia and Tg >40 μg/L in children between different iodine-intake groups.

Conclusions

Thyroid volume and goiter appear to be more sensitive indicators of thyroid stress than thyrotropin and Tg in children with long-term excess iodine intakes. We recommend 250 and 300 μg/d as safe Tolerable Upper Intake Levels of iodine for children aged 7-10 y and 11-14 y, respectively. This trial was registered at www.clinicaltrials.gov as NCT02915536.

Annual Incidence of Thyroid Disease in Patients Who First Time Visit Department for Thyroid Diseases in Tuzla Canton

AIM

The aim of this paper was to evaluate the incidence of thyroid gland diseases in relation to age, sex, existing associated symptoms and thyroxine and thyroid-stimulating hormone levels, in correlation with morphological characteristics and corresponding clinical diagnosis for thyroid gland.

METHODS

Retrospective research was conducted in the period 1-Dec-2017 to 31-Dec-2017 and included a total of 500 subjects of both sexes aged 1 to 80 years. All subjects had clinical examination, which included anamnestic data, palpatory examination of thyroid gland, as well as functional status of thyroid gland.

RESULTS

The results of the research have shown that majority of subjects were females (78.6% vs. 21.4%). The largest number of subjects was in the age group 41 to 60 years. The average age of females was 43.22 years and 42.86 for males. The most common associated symptom for both sexes was related to cardiovascular system disorder (61.2%). Subclinical hypothyroidism was the most prevalent thyroid gland disease (12.8%), while diffuse enlargement of thyroid gland (4.60 %) was the most common in morphological classification. The mean value for free thyroxine for the overall sample was 14.39 pmol/L and 3,4 mlU/L for thyroid-stimulating hormone. Thyroid-stimulating hormone levels were highest in the age group 41-60 years (p=0.043).

CONCLUSION

The overall incidence of thyroid gland diseases was 18.57% for females and 13.08% for males. Free thyroxine levels were highest in thyroid gland with nodular changes and subclinical hypothyroidism (p=0.0001). Thyroid-stimulating hormone levels had the highest value in a thyroid gland with diffuse changes and subclinical hypothyroidism (p=0.0001).

URINARY IODINE CONCENTRATION IS INVERSELY ASSOCIATED WITH THYROGLOBULIN ANTIBODIES

Objective: Epidemiologic studies on the relationship between iodine and thyroid antibodies are inconsistent. Iodine nutrition, genetic, and environmental factors have been shown to modify the effects of iodine on thyroid autoimmunity. We investigated the relationship between urinary iodine concentration (UIC) and thyroglobulin antibodies (TgAbs) in individuals living in iodine-sufficient areas in this cross-sectional study. Methods: A total of 15,008 participants were recruited according to the age range of the population of China in our study. An oral questionnaire was administered to collect basic demographic information. Serum thyrotropin (TSH), thyroid peroxidase antibodies (TPOAbs), TgAbs, and UIC were measured, and thyroid ultrasonography was performed in all subjects. Participants were further divided according to the level of UIC and the status of TgAb, and logistic regression was applied to determine the relationship between UIC and TgAbs. Results: The median UIC of the study population was 205.23 (95% confidence interval [CI], 65.7 to 537.67) μg/L. A total of 17.6% of participants had UIC <100 μg/L. With the increase in UIC, the prevalence of positive TgAbs decreased gradually. UIC level was lowest in subjects with high TgAb titer (median, 182.36 μg/L; 95% CI, 52.88 μg/L to 506.71 μg/L) and highest in the TgAb-negative group (median, 207.16 μg/L; 95% CI, 66.94 μg/L to 538.72 μg/L). Multilinear correlation analysis showed that gender (β = 37.632; P<.001), age (β = 0.467; P = .038), TSH (β = 13.107; P<.001), TPOAb (β = 1.150; P<.001), thyroid volume (β = 2.883; P<.001), and UIC (β = -0.047; P = .032) were independent predictors of TgAb variations. Low UIC (<100 μg/L) was associated with increased risk of positive TgAbs (adjusted odds ratio = 1.255 [1.004 to 1.568]). Conclusion: Low UIC is an independent risk factor for positive TgAb in individuals living in iodine-sufficient areas. Abbreviations: CI = confidence interval; CV = coefficient of variation; FT3 = free triiodothyronine; FT4 = free thyroxine; OR = odds ratio; TgAb = thyroglobulin antibody; TPOAb = thyroid peroxidase antibody; TSH = thyrotropin; UIC = urinary iodine concentration; USI = universal salt iodization.

Increased Incidence Rate of Hypothyroidism After Iodine Fortification in Denmark: A 20-Year Prospective Population-Based Study

OBJECTIVE

To monitor the impact of a cautious iodine fortification (IF) on the incidence of overt hypothyroidism in two subpopulations with different levels of preexisting iodine deficiency (ID).

DESIGN

A 20-year (1997 to 2016) prospective population-based study identified all new cases of diagnosed overt biochemical hypothyroidism in two open cohorts: a western cohort with moderate ID (n = 309,434; 1 January 1997) and an eastern cohort with mild ID (n = 224,535; 1 January 1997). A diagnostic algorithm was applied to all thyroid function tests performed within the study areas, and possible new cases were verified individually. Mandatory IF of salt was initiated in mid-2000 (13 ppm). The current study is a part of the DanThyr study.

RESULTS

At baseline, standardized incidence rates (SIRs) of hypothyroidism were 32.9 and 47.3/100.000/y in the cohorts with moderate and mild ID, respectively. The SIR of hypothyroidism increased significantly in both cohorts after implementing mandatory IF, with peak values of 150% in 2014 to 2016 for the moderate ID cohort and 130% in 2004 to 2005 for the mild ID cohort. Significant increases in SIR were seen among the young and middle-aged participants of both cohorts, whereas no changes were seen among the elderly participants (≥60 years). The follow-up period for the mildly iodine-deficient cohort was restricted up to and including 2008.

CONCLUSION

The cautious initiation of the IF program in Denmark caused a sustained increase in hypothyroidism incidence among subjects residing in areas of moderate and mild ID but only among the young and middle-aged participants.

Hypertension in Thyroid Disorders

Arterial hypertension represents a major global health concern; more than one fourth of the population is affected by high blood pressure. Albeit the underlying cause of the disease remains unclear in the vast majority of the cases, ~10% are of secondary origin. Endocrine disorders are common illnesses and some of them may lead to elevated blood pressure, among which thyroid diseases are of high prevalence and often overlooked, especially in mild cases. Overt and subclinical hyper- and hypothyroidism can both lead to (mostly mild) hypertension; however, the underlying mechanisms are only partially understood. The results of clinical studies are often controversial. During the past decades, some genetic mutations in the hypothalamus-pituitary-thyroid axis with cardiovascular consequences were revealed. Atherosclerotic changes resulting from lipid abnormalities due to thyroid dysfunction also affect the vasculature and can cause elevated blood pressure. The review gives a synopsis of our knowledge how thyroid hormone metabolism and functional thyroid diseases affect the cardiovascular system, their negative impact and causative role in the development of hypertension.

Relation of Different Components of Climate with Human Pituitary-Thyroid Axis and FT3/FT4 Ratio: A Study on Euthyroid and SCH Subjects in Two Different Seasons

BACKGROUND

Various changes in thyroid hormones (TH) and thyroid-stimulating hormone (TSH) level were observed in different seasons among euthyroid and hypothyroid subjects living in areas with an extreme temperature difference between summer and winter.

OBJECTIVES

This study aims at finding the effect of temperate climate on the seasonal variations of TSH and TH in euthyroid and subclinical hypothyroidism (SCH) subjects and at evaluating if the test season has an effect on the number of subjects diagnosed as SCH. It basically focuses on the relation of different components of climate with TH and TSH.

METHOD

In a prospective study on 152 healthy (euthyroid) volunteers and 25 SCH subjects, the serum hormone levels (TSH, FT4, and FT3) were measured in both the summer and winter seasons and correlated with all the climate components using Pearson's correlation coefficient. The effect of duration of outdoor exposure on hormone levels was compared using a paired sample t-test (P < 0.05).

RESULTS

Small but statistically significant increased FT3 level and decreased FT4 level were observed during the winter season in euthyroid and SCH subjects, respectively. There was a significant negative correlation between FT3 and FT3/FT4 ratio with temperature and sunshine duration and a positive correlation with humidity and atmospheric pressure. A positive correlation was found between FT4 and sunshine duration.

CONCLUSION

The climate components contributed to the slight variance in hormone levels in different seasons, and the effect was mostly on peripheral conversion of FT4 to FT3 rather than the pituitary-thyroid axis leading to slightly higher FT3 in winter. Seasonal variation does not affect the diagnosis of SCH cases.

Iodine intake and chronic autoimmune thyroiditis: a comparative study between coastal and mainland regions in Greece

INTRODUCTION

The purpose of this study was to evaluate the relationship between iodine intake and autoimmune thyroiditis in Chios, an island located in the North East Aegean Sea, in comparison to mainland regions in South Western Greece (SWG).

MATERIALS AND METHODS

Urine iodine concentration (UIC), thyroid function (serum TSH, thyroid autoantibodies: anti-TPO and anti-Tg), and thyroid U/S were assessed in 200 subjects (150 females and 50 males) from Chios and 322 subjects (255 females and 67 males) from several mainland regions in SWG. All participants were recruited from outpatient clinics and were diagnosed as euthyroid.

RESULTS

Median UIC in Chios was significantly higher compared to SWG (136.1 vs. 104.5 μg/L, p < 0.001), indicating that both regions are iodine sufficient according to World Health Organization (WHO) criteria. The prevalence of thyroid autoimmunity was 66.5% in Chios and 27% in SWG, significantly higher in females (46.7%) than in males (26.5%). Furthermore, individuals with increased levels of thyroid autoantibodies either anti-TPO or anti-Tg (TAbs) showed increased median UIC levels compared to those / subjects / patients with normal levels (126.7 vs. 108.95 μg/L, p < 0.001). Serum TSH mean values (mIU/L) were greater in females (mean = 2.1 ± 1.41) compared to males (mean = 1.82 ± 1.26) (p = 0.04) and decreased with age.

CONCLUSIONS

In conclusion, in the present study, we clearly indicate that increased thyroid autoimmunity is positively associated with increased iodine intake, as well as with the female gender. Moreover, iodine intake and thyroid autoimmunity appear to be significantly higher in a coastal region (Chios) than in mainland Greece (SWG). Additional environmental factors, apart from iodine, should be investigated in future studies. Mean TSH values were increased in females and decreased with age. The latter is probably due to the presence of autonomous goiter in older Greek populations, as a result of long-term status of iodine deficiency in the past.

Thyroid status in premenopausal and postmenopausal women - A biochemical study on insulin resistance in non obese, overweight and obese type 2 diabetics

BACKGROUND

Insulin resistance with altered thyroid status in women is observed in type 2 diabetics and varies with advancing age and estrogen profile. We compared thyroid status between premenopausal and postmenopausal women in obese, non obese and overweight type 2 diabetes.

METHODOLOGY

We included 301type 2 diabetics who were segregated into premenopausal (n = 100) 33.2% and postmenopausal (n = 201) 66.8% among three sub groups (Non obese, overweight and Obese).Anthropometry, fasting blood glucose, lipid profile, glycated hemoglobin, homeostasis model assessment of insulin resistance, liver function tests, Free T4, T3, TSH, Zn²⁺and Mg²⁺ were enabled.

RESULTS

Non obese type 2 diabetics were segregated into two groups n = 21 (29.2%)- premenopausal with mean age of 41.48 ± 4.30 and n = 51 (70.8%) - post menopausal with mean age of 58.49 ± 7.32 There were significant differences in WHR, HbA1c, HDL with p < 0.05 and ALP with p < 0.01; Overweight type 2 diabetics n = 55 (37.9%) -premenopausal with mean age of 41.96 ± 3.80 and n = 90 (62.1%)- post menopausal with mean age of 57.80 ± 7.20. There were significant differences in Urea, Zinc, Total protein, Albumin with p < 0.05 and T4, TSH with p < 0.01. Obese Type 2 diabetics n = 24 (28.6%) -premenopausal with mean age of 42.00 ± 4.30 and n = 60 (71.4%) -post menopausal with mean age of 57.80 ± 7.20. There were significant differences in Urea, Magnesium, Triacylglycerols, and VLDL with p < 0.05, Insulin and HOMA-IR with p < 0.01.

CONCLUSION

Anthropometry specified classification of type 2 diabetics in pre and postmenopausal women reflects thyroid status.

Non-immune-related hypothyroidism and its relationship with excess iodine

PURPOSE

In iodine-sufficient areas, autoimmune hypothyroidism has been regarded as the major subtype of hypothyroidism. Non-immune-related hypothyroidism has received little attention because it is considered to be rare. The aim of this study was to evaluate the prevalence of non-immune-related hypothyroidism in Korea and to identify its associating factors.

METHODS

A total of 6434 participants in the Korea National Health and Nutrition Examination Survey VI (2013-2015) without known thyroid disease who were examined for thyroid stimulating hormone, free thyroxine, TPO Ab, and urine iodine concentration (UIC) were enrolled. The weighted proportions, demographic variables, and severity of immune-related and non-immune-related hypothyroidism were compared. To assess the effect of iodine on hypothyroidism in TPO Ab positive or negative populations, the weighted prevalence of hypothyroidism was assessed in each population according to UIC or estimated iodine intake subgroups.

RESULTS

The prevalence of undetected hypothyroidism in Korea was 3.8% (n = 233). Of these 233 cases, 171 (71.8%) were non-immune-related. In the TPO Ab negative population, the prevalence of hypothyroidism was increased significantly in the subgroup with UIC between 250 and 749 µg/L (HR 2.12 [1.17, 3.83]) and ≥ 750 µg/L (HR 3.42 [1.93, 6.04]) or the subgroups with estimated iodine intake ≥ 750 µg/day (HR 2.81 [1.64, 4.80]).

CONCLUSIONS

This nationwide study demonstrated that most cases of hypothyroidism in iodine-sufficient areas are non-immune-related and are associated with excess iodine above a certain level. More attention to this unrecognized but widespread potential health risk is needed.