A sensitive thyroid stimulating hormone assay for screening of thyroid functional disorder in elderly Japanese

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.

Hemodilution Impacts Assessment of Thyroid Status before and after Hemodialysis in Patients with End-Stage Renal Disease

BACKGROUND

To elucidate the role of hemodilution in the alteration of thyroid hormone levels in end-stage renal disease (ESRD), we compared thyroid function before and after hemodialysis (HD).

METHODS

Twenty-three male ESRD patients (age <65 years) with either chronic glomerulonephritis (CGN) or diabetic nephropathy (DN), who were enrolled between June 2019 and August 2019, were included in the study. The free thyroxine (fT4), free tri-iodothyronine (fT3), and thyroid-stimulating hormone (TSH), thyroxine-binding globulin (TBG), and thyroglobulin (Tg), measured before and after HD in 12 patients with CGN (48.7 ± 11.8 years [mean ± standard deviation]) and 11 patients with DN (57.6 ± 6.5 years), were compared with 45 healthy controls (52.5 ± 11.9 years).

RESULTS

The fT4, fT3, and TBG were significantly low before HD and increased in parallel with an increase in hematocrit and albumin after HD in both ESRD subgroups. The TSH was high before HD and decreased significantly after HD, while Tg remained almost unchanged. In DN, the fT4 levels were nearly identical, while fT3 was lower with slightly higher TSH, compared with CGN. The TSH/fT4 ratios before HD were significantly higher in both subgroups, and the fT3/fT4 ratios after HD were significantly lower in DN than the control.

CONCLUSIONS

Our findings suggest that the low fT4 and fT3 levels found in ESRD are due to hemodilution before HD, resulting in a slightly higher TSH level but almost unchanged Tg level, and that DN is associated with decreased T4-to-T3 conversion.

Age-sex disparities and sub-clinical hypothyroidism among patients in Tikur Anbesa Specialized Hospital, Addis Ababa, Ethiopia

BACKGROUND

Subclinical hypothyroidism is an elevation in serum thyroid-stimulating hormone above the upper limit of the reference range (0.45-4.5 mIU/L) with normal serum TT4 and TT3 concentration. The most important implication of subclinical hypothyroidism is high likelihood of progression of clinical hypothyroidism.

METHODS

Institution-based cross-sectional study was conducted on medical records of patients referred at endocrine clinic Tikur Anbesa Specialized Hospital, Addis Ababa from 2010 to 2016. This study was conducted from normal ambulatory patients who have come in the hospital outpatient department since they experienced abnormality on their health status. During the study period, patients were complaining about their clinical symptoms. A total number of 9000 patients were included. Patients' card was retrieved by using standard extracted formats to collect socio-demographic and clinical information and laboratory measurements. Serum TSH, TT4, and TT3 levels were determined by electro-chemiluminescence immunoassay method on ECLIA 2010 fully automatic analyzer at TASH nuclear medicine. SPSS 20 version software was used for analysis, and chi-square test was used to check the association between dependent and independent variables.

RESULTS

The overall prevalence of subclinical hypothyroidism evaluated to be 582 (6.47%), 4.6% in females and 1.9% in males. Four hundred and thirty-one (74%) patients had serum TSH levels between 5 and 10 mIU/L, and the average TSH level of subclinical hypothyroid patients whose age was ≥ 40 differ significantly from that of subclinical hypothyroid patients whose age was < 40. The average TSH level among female patients whose age are ≥ 40 differed significantly from their counterparts. Subclinical hypothyroidism patients more often reported having dry skin, poor memory, fatigue, cold intolerance, constipation, and hoarseness.

CONCLUSION

The overall prevalence of ScHt was 6.5% where females showed higher level than males. Age ≥ 40 became independent factor of subclinical hypothyroidism. The higher prevalence of subclinical hypothyroidism in this study could become a predictor for overt hypothyroidism, so screening for subclinical hypothyroidism prevents the later development of complicated overt hypothyroidism.

The first report of the thyroid function of haemophilic patients with HIV/HCV co-infection in Japan

INTRODUCTION

A high incidence of thyroid dysfunction is reported in patients with HIV or HCV mono-infection. We have conducted a periodic medical examination including the thyroid function for haemophilic patients with HIV/HCV co-infection due to contaminated blood products.

METHODS

We examined the thyroid function (as assessed by the FT3, FT4 and TSH levels) in 45 haemophilic patients, including thyroglobulin and auto-antibody, antithyroglobulin antibody, antithyroid peroxidase antibody and anti-TSH receptor antibody in 28 patients.

RESULTS

All the patients were males (median age: 42 years; range: 29-66). The median values of thyroid function were FT3 3.36 pg mL(-1) , FT4 1.125 ng mL(-1) and TSH 1.65 μIU mL(-1) . Five patients (11.1%) had high TSH levels. In 28 patients in whom the presence of auto-antibodies was examined, the median age was 47 years of age. The median value of thyroglobulin was 16 ng mL(-1) and two patients showed high levels of thyroglobulin. The presence of anti-TSH receptor antibody of all the patients was negative, but one patient (3.5%) was positive of antithyroid peroxidase antibody and antithyroglobulin antibody.

CONCLUSIONS

Since 0.68-3.6% of the general healthy population is reported to show hypothyroidism, our data showed that the proportion of hypothyroidism in haemophilic patients with HIV/HCV co-infection was more frequent than that of the normal population.

The Effect of Hypothyroidism on a Composite of Mortality, Cardiovascular and Wound Complications After Noncardiac Surgery: A Retrospective Cohort Analysis

BACKGROUND

We tested the hypothesis that hypothyroidism, as defined by thyroid-stimulating hormone (TSH) concentration, is associated with a severity-weighted composite of mortality and major cardiovascular and infectious complications after noncardiac surgery.

METHODS

In this retrospective cohort study, we evaluated adults at the Cleveland Clinic Main Campus between 2005 and 2012, who had had available TSH concentrations within the 6 months before noncardiac surgery. Patients were categorized as (1) hypothyroid (patients who had diagnosis of hypothyroidism any time prior to surgery and increased TSH value (> 5.5 mIU/L) within 6 months prior to surgery); (2) treated (hypothyroid diagnosis and normal TSH concentrations [0.4-5.5 mIU/L]); and (3) euthyroid (no hypothyroid diagnosis and normal TSH concentrations). We conducted pairwise comparisons among the 3 groups using inverse propensity score weighting to control for observed confounding variables. Average relative effect generalized estimating equation model was used for the primary outcome composite of in-hospital cardiovascular morbidity, surgical wound complication or infection, and mortality. Logistic regression and Cox proportional hazards regression were used for secondary outcomes of intraoperative vasopressor use and duration of hospitalization, respectively.

RESULTS

We identified 800 hypothyroid patients (median TSH: 8.6 mIU/L [Q1, Q3: 6.5, 13.0]), 1805 treated patients (2.0 mIU/L [1.1, 3.2]), and 5612 euthyroid patients (1.7 mIU/L [1.1, 2.6]). There were no significant differences among the hypothyroid, treated, and euthyroid patients on the primary composite outcome (all P values ≥0.30). Hypothyroid patients were slightly more likely to receive vasopressor during surgery than either treated (odds ratio, 1.17; 99.2% confidence interval [CI], 1.01-1.36) or euthyroid (odds ratio, 1.12; 99.2% CI, 1.02-1.24) patients. Furthermore, hypothyroid patients were slightly but significantly less likely to be discharged at any given postoperative time than treated patients (hazard ratio, 0.92; 99.2% CI, 0.86-0.99).

CONCLUSIONS

Hypothyroidism was not associated with worse postoperative mortality, wound, or cardiovascular outcomes in noncardiac patients. Thus, postponing surgery to initiate thyroid replacement therapy in patients with hypothyroidism seems unnecessary.

Importance of specific reference values for evaluation of the deteriorating thyroid function in patients with end-stage renal disease on hemodialysis

BACKGROUND/AIM

We evaluated the thyroid function in end-stage renal disease (ESRD) on maintenance hemodialysis.

MATERIAL/METHODS

Thyroid function and clinical hypothyroid score were evaluated in 145 ESRD patients.

RESULTS

Comparison of thyroid function between 127 ESRD patients, excluding 18 patients with suppressed or elevated serum TSH level, and age/sex-matched healthy controls (76 in midlife group aged under 65 and 51 in late-life group aged 65 or over) using a multivariate logistic regression analysis suggested significant difference (P < 0.0001), mainly in serum fT4 level (P = 0.0099) and age (P = 0.0492), but not in serum fT3 (not significant; ns), TSH (ns) level or fT3/fT4 ratio (ns). Serum fT3 level and fT3/fT4 ratio were significantly lower (P < 0.001) in late-life group only in ESRD. Reference values calculated for midlife ESRD patients, such as 0.6-1.3 ng/dl for fT4 compared with 0.8-1.7 ng/dl for healthy control, were helpful for the diagnosis of mild but definite hyperthyroidism in whom serum fT4 level was 1.5 ng/dl. The prevalence of primary thyroid dysfunction, compared with the values for ESRD, was 0.7 % for hyperthyroidism, 1.4 % for overt hypothyroidism and 10.3 % for subclinical hypothyroidism. Hypothyroid score was high among those with ESRD independent of thyroid dysfunction.

CONCLUSIONS

Serum fT4 level was markedly lower without a change in fT3/fT4 ratio in ESRD. This may suggest typical carbohydrate-sufficient non-thyroidal illness. The specific reference values for ESRD were useful to evaluate borderline thyroid dysfunction and to evaluate the prevalence of the patients with primary thyroid dysfunction in ESRD.

Autoimmune thyroid disease in children and adolescents with idiopathic pulmonary arterial hypertension

BACKGROUND

Previous studies have reported a high prevalence of autoimmune thyroid disease (AITD) in adult patients with pulmonary arterial hypertension (PAH). The aim of this retrospective study was to determine the prevalence of AITD in children and adolescents with idiopathic PAH (IPAH).

METHODS AND RESULTS

The study group included 16 patients who had been diagnosed as having idiopathic PAH when they were younger than 15 years old; all were younger than 20 years of age. Thyroid function and antithyroid antibody levels were examined regularly at 6-12-month intervals and when there were clinical signs of thyroid dysfunction. In total, 7 patients (44%) had AITD; 2 patients developed Graves' disease, 2 developed silent thyroiditis, and 3 had antithyroid antibodies with euthyroidism. The duration after PAH onset and the prostacyclin (PGI(2)) treatment period were significantly longer in patients with AITD (7.6+/-2.1 and 7.4+/-2.3 years, respectively) than in patients without AITD (5.0+/-1.1 and 4.8+/-1.2 years, respectively; P<0.01 and P<0.05).

CONCLUSIONS

The prevalence of AITD is high in children and adolescents with IPAH, so evaluation of thyroid function is important to prevent deterioration of right heart failure.

Thyroid function in Japanese adults as assessed by a general health checkup system in relation with thyroid-related antibodies and other clinical parameters

BACKGROUND

A limited number of epidemiological studies have attempted to assess thyroid function in the general population of iodine-sufficient countries. The aim of the present study was to determine the underlying thyroid diseases responsible for abnormal thyroid function detected by a general health checkup system in Japan, and to characterize the lipid metabolism in subjects found to have thyroid dysfunction.

METHODS

Serum thyrotropin (TSH), free thyroxine, anti-thyroglobulin antibodies (TgAb), anti-thyroid peroxidase antibodies (TPOAb), and TSH-binding inhibitor immunoglobulins (TBII) were determined in 1818 Japanese adults (804 men and 1014 women; mean age 51.3 +/- 9.0 years) who undertook a general health checkup.

RESULTS

Of the 1818 examinees, 12 (0.7%) had overt hypothyroidism (OH), 105 (5.8%) subclinical hypothyroidism, 13 (0.7%) overt thyrotoxicosis, and 39 (2.1%) subclinical thyrotoxicosis. TgAb or TPOAb tests were positive in 17.7% of men and 31.4% of women. The prevalence of positive tests for TgAb or TPOAb was 14.8% for men and 23.4% for women without palpable goiter. Positive tests for TgAb, TPOAb, TBII, and a palpable goiter were more common in subjects with abnormal thyroid function tests than in subjects with normal thyroid function. At the time that abnormal thyroid function test results were first obtained, the signs of thyrotoxicosis were mild or even absent in all 13 subjects with overt thyrotoxicosis, 8 of whom had Graves' disease and 5 of whom had painless thyroiditis. Of the 12 patients with OH, only 2 patients had a palpable goiter. In the OH group, TgAb tests were positive in eight, TPOAb tests were positive in eight, and TBII tests were positive in two. The prevalence of disturbed lipid metabolism, when adjusted for age, was significantly higher in the subclinical hypothyroidism group than in normal controls (p < 0.001; odds ratio, 1.67; 95% confidence interval, 1.10-2.51).

CONCLUSIONS

In Japanese adults who chose to be screened by a general health checkup system, the prevalence of abnormal thyroid function was nearly 10%. In a high percentage of these patients, abnormal thyroid function could not be detected by their history or physical examination. Just a physical examination without thyroid function tests, particularly serum TSH levels, was not adequate even when performed by a thyroid specialist.

An analysis of the natural course of subclinical hyperthyroidism

BACKGROUND

Our aim was to evaluate the incidence rate of overt hyperthyroidism in a cohort of patients with subclinical hyperthyroidism and to assess the potential risk factors for the development of overt thyroid hyperfunction.

METHODS

We performed a retrospective analysis in 75 patients (68 women, mean age 62.2 +/- 14.2 years) with subclinical hyperthyroidism and different grades of serum thyrotropin (TSH) suppression. Incidence rate of overt hyperthyroidism and survival time, ie, time without requiring therapy for overt hyperthyroidism, were studied.

RESULTS

Thirty-four patients (45.3%) developed overt hyperthyroidism and 15 (20.0%) reverted to normal TSH values. The incidence rate of overt hyperthyroidism was 9.69 cases per 100 patient-year in the whole population and 4.12, 7.41, and 29.63 cases per 100 patient-year in subjects with initial TSH values of 0.30 to 0.49, 0.10 to 0.29, and <0.10 mU/L, respectively. Kaplan-Meier analysis of survival time curves showed that the development of overt thyroid hyperfunction was significantly related to the presence of symptoms of hyperthyroidism (P < 0.05) and low (<0.10 mU/L) TSH concentrations (P < 0.001). A stepwise multivariate Cox regression analysis showed that both symptoms and low TSH values were significant factors for progression to overt thyrotoxicosis.

CONCLUSIONS

TSH concentration is the most powerful predictor in the outcome of patients with subclinical hyperthyroidism. Our results suggest that patients with values under 0.10 mU/L have the highest probability to develop overt thyroid hyperfunction. In patients with TSH values higher than this value, the risk of progression is notably lower.

Estimated dietary intake of thiocyanate from Brassicaceae family in Korean diet

Glucosinolate, sulfur-containing organic anions bonded to glucose, is found in plants including the family of Brassicaceae. Glucosinolate is hydrolyzed by myrosinase and produces various by-products that possess biological activities. Among the decomposed products, thiocyanate is known for its adverse effects on thyroid metabolism due to competition with iodine. This is of concern in that Korean dietary habits consist of consumption of large amounts of Brassicaceae vegetables such as cabbage and radishes, which may be correlated with high incidence of thyroid dysfunction. Thus, quantification of thiocyanate in Brassicaceae vegetables was performed by hydrolysis and spectrophotometrical detection. Average daily intake of Brassicaceae vegetables was obtained from the Third Korea National Health and Nutrition Examination Survey (KNHANES III), 2005-Nutrition Survey and from The Vegetable Production Statistics, 2007. Average daily intake of thiocyanate through Brassicaceae vegetables in Korea was estimated to be 16.3 micromol SCN(-)/d/person. When this was compared to published animal studies, average thiocyanate intake per person was lower than doses required to produce adverse effects. However, further studies may be warranted to ensure safety with sufficient margins of safety.

The regulatory T cell gene FOXP3 and genetic susceptibility to thyroid autoimmunity: an association analysis in Caucasian and Japanese cohorts

FOXP3 is a key gene in the development of regulatory T cells (Treg). FOXP3 expression commits naïve T cells to become Treg cells. Indeed, mutations in the FOXP3 gene cause severe systemic autoimmune diseases in humans and in mice. Therefore, we hypothesized that the FOXP3 gene may be associated with thyroid autoimmunity which is among the typical autoimmune diseases that develop in individuals with FOXP3 mutations. Moreover, the FOXP3 gene is located within an X-chromosome locus (Xp11.23) previously shown to be linked with autoimmune thyroid diseases (AITD). We tested the FOXP3 gene locus for association with AITD in two large cohorts of US Caucasians and Japanese AITD patients. We analyzed 269 Caucasian AITD patients (52 males and 217 females) and 357 Caucasian controls (159 males and 198 females), as well as 377 female Japanese AITD patients and 179 female Japanese controls. The FOXP3 gene locus was analyzed using four microsatellite polymorphisms [(GT)n; (TC)n; DXS573; DXS1208] flanking the FOXP3 gene locus. Interestingly, while no association was found between FOXP3 polymorphisms and AITD in the Japanese cohort there was a significant association in the Caucasian cohort. There was a significant association of the (TC)n polymorphism with AITD in the Caucasian male AITD patients (p=0.011; 5 degrees of freedom [df]). Similarly, there was an association between the DXS573 microsatellite and AITD in the Caucasian female AITD patients (p=0.00023; 4 df). These results suggest that polymorphisms of the FOXP3 gene may play a role in the genetic susceptibility to AITD in Caucasians, perhaps by altering FOXP3 function and/or expression.

Achalasia and thyroid disease

AIM: To investigate some possible etiologies of achalasia by screening patients with achalasia for some autoimmune diseases such as thyroid disease.

METHODS: We examined 30 known cases of achalasia (20 females, 10 males). Their age ranged 15-70 years. All of them were referred to our institute for treatment. Their sera were evaluated to detect some possible associations with rheumatoid disease, thyroid disease, inflammatory process, anemia, etc.

RESULTS: Seven out of 30 patients (23%) had thyroid disease including four patients with hypothyroidism (13.3%), two patients with hyperthyroidism (6.6%), and one had only thyroid nodule but was in euthyroid state (3.3%). Two of these hypothyroid patients had no related clinical symptoms (subclinical) and two had clinical manifestations of hypothyroidism. There were no correlations between the intensity of thyroid diseases and the severity of achalasia symptoms.

CONCLUSION: The etiology of achalasia is unknown although autoimmunity has been implicated and is supported by several studies. Thyroid disease presents concomitantly with achalasia in about one fourth of our patients who may have a common etiology.

Hypothyroidism after radiotherapy for patients with head and neck cancer

We report on 2 cases of hypothyroidism presenting clinical symptoms that occurred after radiotherapy for cancer of the head and neck and on the results of estimating thyroid function in patients with head and neck cancer who received radiotherapy. The first patient underwent total laryngectomy for laryngeal cancer without sacrificing the thyroid gland and partial gastrectomy for gastric cancer. Radiotherapy of the neck was carried out postoperatively. Two years later, the patient developed chest pain; pericardial effusion was detected, leading to a diagnosis of myxedema caused by hypothyroidism. The second patient received radiotherapy alone for laryngeal cancer. Two months later, low serum sodium concentration and anemia were detected in this patient. The cause of these changes was subsequently found to be hypothyroidism. Based on our experience with these 2 cases, we measured thyroid function in 35 patients who had undergone neck radiation for head and neck cancer at our hospital over the past 10 years. Hypothyroidism was observed in 13 of the 35 patients (37%). The prevalence of hypothyroidism was 46% (6/13) for patients treated with both radiation and surgery, as compared with 32% (7/22) for those who received radiation alone. The risk factors responsible for hypothyroidism were not evident from the statistical analysis of these cases. We believe that thyroid function should be evaluated periodically in patients who have undergone neck radiation because it is often difficult to diagnose hypothyroidism only from clinical symptoms.

Immunogenetics of Hashimoto's thyroiditis

Hashimoto's thyroiditis (HT) is an organ-specific T-cell mediated disease. It is a complex disease, with a strong genetic component. To date, significant progress has been made towards the identification and functional characterization of HT susceptibility genes. In this review, we will summarize the recent advances in our understanding of the genetic input to the pathogenesis of HT.

Searching for the autoimmune thyroid disease susceptibility genes: from gene mapping to gene function

The autoimmune thyroid diseases (AITD) are complex diseases that are caused by an interaction between susceptibility genes and environmental triggers. Genetic susceptibility, in combination with external factors (e.g., dietary iodine), is believed to initiate the autoimmune response to thyroid antigens. Abundant epidemiological data, including family and twin studies, point to a strong genetic influence on the development of AITD. Various techniques have been used to identify the genes contributing to the etiology of AITD, including candidate gene analysis and whole genome screening. These studies have enabled the identification of several loci (genetic regions) that are linked with AITD, and in some of these loci putative AITD susceptibility genes have been identified. Some of these genes/loci are unique to Graves' disease (GD) and Hashimoto's thyroiditis (HT), and some are common to both diseases, indicating that there is a shared genetic susceptibility to GD and HT. The putative GD and HT susceptibility genes include both immune modifying genes (e.g., human leukocyte antigen, cytotoxic T lymphocyte antigen-4) and thyroid-specific genes (e.g., TSH receptor, thyroglobulin). Most likely these loci interact, and their interactions may influence disease phenotype and severity. It is hoped that in the near future additional AITD susceptibility genes will be identified and the mechanisms by which they induce AITD will be unraveled.

High serum TSH levels are associated with depression in the elderly

In order to investigate the association between elevated serum TSH levels and depression in the elderly, we conducted a population-based study of 451 over 60-year-old outpatients of a general University Hospital. Patients were divided into Group I (GI) (248 individuals) with high serum TSH levels, but otherwise no important condition or disease, and Group II (GII) (203 patients) with no previous diagnosis of thyroid or mood disease, referred to the hospital because of nonthyroidal severe diseases. All patients were clinically examined and classified according to DMS-IV for mood disturbance and had serum TSH, free T4 levels and antithyroid antibodies measured. High serum TSH levels (11.6+/-14.8 mU/l) were observed in 65/203 (32%) patients of GII. Among these patients, 42/65 (65%) had normal free T4 concentrations (1.23+/-0.98 ng/dl), no clinical manifestation of hypothyroidism and thus were considered to present subclinical hypothyroidism. Depression was observed in 24 cases from GI (9.7%) and 29 from GII (14.3%) and was frequent in the subclinical hypothyroid patients (49%). Our results suggest that mood disturbances are frequent in the elderly with elevated serum TSH levels, but they do not differ in the primary hypothyroid and the nonthyroidal sick patients.

Estudo da Função Tiroideana em Uma População com Mais de 50 Anos

Com objetivo de analisar a freqüência de disfunção tiroideana e de identificar possíveis alterações hormonais decorrentes do envelhecimento, estudamos 198 indivíduos com idade variando de 50 a 85 anos e 106 filhos com idade entre 11 e 49 anos. A prevalência de disfunção tiroideana foi semelhante em ambos grupos (12,6% no grupo de estudo e 14,1% entre os filhos). A presença de um ou dois anticorpos antitiroideanos positivos foi também semelhante entre os grupos (9,1% e 12,3% para os idosos e filhos respectivamente), embora sem correlação disfunção tiroideana. nos idosos. Os níveis séricos de T3 e FT4 foram significantemente menores entre os indivíduos mais velhos quando comparados com os filhos (1,27±0,27 x 1,39±0,31 ng/ml e 0,97±0,29 x 1,18±0,76 ng/dl, respectivamente). Não houve diferença entre os grupos quanto aos níveis de TSH, T4 total e TBG. Concluímos que a prevalência de disfunção tiroideana não foi diferente entre os grupos e que a presença de anticorpos antitiroideanos esteve associada com disfunção da tiróide apenas nos indivíduos mais jovens. A correlação inversa dos níveis de T3 e FT4 com a idade pode refletir uma adaptação à menor necessidade dos hormônios com o envelhecimento.

Epidemiology and prevention of clinical and subclinical hypothyroidism

Iodine deficiency is the most common cause of hypothyroidism worldwide. In persons living in iodine-replete areas, causes are congenital, spontaneous because of chronic autoimmune disease (atrophic autoimmune thyroiditis or goitrous autoimmune thyroiditis [Hashimoto's thyroiditis]), or iatrogenic because of goitrogens, drugs, or destructive treatment for thyrotoxicosis. Screening for congenital hypothyroidism exists and its use prevents mental retardation. The prevalence of spontaneous hypothyroidism is between 1% and 2% and is more common in older women and 10 times more common in women than in men. A significant proportion of subjects have asymptomatic chronic autoimmune thyroiditis and 8% of women (10% of women over 55 years of age) and 3% of men have subclinical hypothyroidism. Approximately one third of patients with newly diagnosed overt hypothyroidism have received destructive therapy for hyperthyroidism and indefinite surveillance is required. There is not much that can be done to prevent the occurrence of spontaneous autoimmune hypothyroidism, but if identified early, something can be done to prevent progression to overt disease. Controversy exists as to whether healthy adults would benefit from screening for autoimmune thyroid disease because a significant proportion of subjects tested will have evidence of mild thyroid failure. Case finding in women at menopause or visiting a primary care physician with nonspecific symptoms appears justified.

Environmental iodine intake affects the type of nonmalignant thyroid disease

The relationship between the iodine intake level of a population and the occurrence of thyroid diseases is U-shaped with an increase in risk from both low and high iodine intakes. Developmental brain disorders and endemic goiter caused by severe iodine deficiency may seriously deteriorate overall health status and economic performance of a population. Severe iodine deficiency with a median 24-hour urinary iodine excretion of the population below 25 microg needs immediate attention and correction. Less severe iodine deficiency with median urinary iodine excretion below 120 microg per 24 hours is associated with multinodular autonomous growth and function of the thyroid gland leading to goiter and hyperthyroidism in middle aged and elderly subjects. The lower the iodine intake, the earlier and more prominent are the abnormalities. At the other end of the spectrum, severely excessive iodine intake starting at median urinary iodine excretion levels around 800 microg per 24 hours is associated with a higher prevalence of thyroid hypofunction and goiter in children. A number of studies indicate that moderate and mild iodine excess (median urinary iodine >220 microg per 24 hours) are associated with a more frequent occurrence of hypothyroidism, especially in elderly subjects. The exact mechanism leading to this has not been clarified, and more studies are needed to define the limits of excessive iodine intake precisely. Due to the frequent occurrence of thyroid disorders, proper monitoring and control of the population iodine intake level is a cost-effective alternative to diagnosing, therapy and control of the many individual cases of thyroid diseases that might have been prevented.

Thyroid disorders in mild iodine deficiency

Comparative epidemiologic studies in areas with low and high iodine intake and controlled studies of iodine supplementation have demonstrated that the major consequence of mild-to-moderate iodine deficiency for the health of the population is an extraordinarily high occurrence of hyperthyroidism in elderly subjects, especially women, with risk of cardiac arrhythmias, osteoporosis, and muscle wasting. The hyperthyroidism is caused by autonomous nodular growth and function of the thyroid gland and it is accompanied by a high frequency of goiter. Pregnant women and small children are not immediately endangered but the consequences of severe iodine deficiency for brain development are grave and a considerable safety margin is advisable. Moreover, a shift toward less malignant types of thyroid cancer and a lower radiation dose to the thyroid in case of nuclear fallout support that mild-to-moderate iodine deficiency should be corrected. However, there is evidence that a high iodine intake may be associated with more autoimmune hypothyroidism, and that Graves' disease may manifest at a younger age and be more difficult to treat. Hence, the iodine intake should be brought to a level at which iodine deficiency disorders are avoided but not higher. Iodine supplementation programs should aim at relatively uniform iodine intake, avoiding deficient or excessive iodine intake in subpopulations. To adopt such a strategy, surveillance programs are needed.

Population screening for autoimmune thyroid disease

Whether or not healthy adults in the community would benefit from screening for autoimmune thyroid disease is controversial. Although the prevalence of unsuspected overt thyroid disease is low, a significant proportion of subjects tested will have evidence of mild thyroid failure or excess. This article assesses whether subclinical thyroid disease is of sufficient clinical importance to warrant screening and, once detected and confirmed, to justify therapy. Population screening for autoimmune thyroid disease is assessed against recently revised screening criteria, using data from epidemiologic studies. Recommendations are proposed that may be applied in any iodine-replete community.

The blood spot thyrotropin method is not adequate to screen for hypothyroidism in the elderly living in abundant-iodine intake areas: comparison to sensitive thyrotropin measurements

We investigated whether the blood spot thyrotropin (TSH) method was adequate for screening elderly subjects with abundant iodine intake (median excretion 330 microg/g creatinine) for hypothyroidism. In 97 healthy adults (group A), 210 nursing home residents (group B) and 265 elderly subjects living at home (group C) serum (sensitivity < 0.02 mU/L, cost 1.2 U.S. dollars [USD]) and blood spot TSH (sensitivity < 1.0 mU/L, cost 0.4 USD) were measured, and the sensitivity and specificity of different blood spot TSH cutoff points to detect cases with elevated serum TSH were calculated. Elevated (> 3.5 mU/L) serum TSH levels (group A, 6.2%; group B, 16.2%; group C, 22.3%; B > A, p = 0.025; C > A, p < 0.001) were detected with the required sensitivity of greater than 0.9 only if the cutoff point of the blood spot TSH was set as low as 2.5 mU/L, but this led to a considerable loss of specificity. At cutoff point 2.5 mU/L, the rate of positivity was 39.3% and the cost of blood spot screening/person increased to 0.88 USD, considering that positive cases have to be rechecked by serum TSH to exclude false positivity. Cases with significantly elevated (> 10.0 mU/L) serum TSH (group A, 1.03%; group B, 2.85%; group C, 2.20%) were detected at blood spot cutoff points 10.0-4.0 mU/L with a sensitivity of 1.0 and without considerable loss of specificity. We conclude that while screening for hypothyroidism in the elderly population with abundant iodine intake is justified by the high prevalence of elevated ultrasensitive serum TSH values, the sensitivity of the blood spot method is insufficient to detect the subclinical hypothyroidism accurately and would, therefore, fail to detect most affected subjects.

Low incidence rate of overt hypothyroidism compared with hyperthyroidism in an area with moderately low iodine intake

In areas with relatively high iodine intake, the incidence rate of hypothyroidism is several-fold higher than that of hyperthyroidism. Recently, we found a similarly high prevalence rate of subclinical hypothyroidism compared with hyperthyroidism in a high iodine intake area, while a relatively low prevalence of subclinical hypothyroidism was observed in a low iodine intake area. In the present study we compared the incidence rate (newly diagnosed in primary care and at hospital) of overt hypothyroidism with that of hyperthyroidism in a well-defined geographical area in Jutland, Denmark, with an iodine intake around 60 microg/day. The number of personsxyears studied was 569,108. Data on hyperthyroidism have been published previously. The overall incidence of hypothyroidism was 13.5/100,000 per year (F/M 22.9/3.6), hyperthyroidism 38.7/100.000 per year (F/M 63.0/13.0). The incidence of hypothyroidism was steadily increasing with age up to 80/100,000 per year in subjects older than 70 years of age, but apart from congenital hypothyroidism it was lower than that of hyperthyroidism at all ages. The majority of patients (79%) was diagnosed to have spontaneous autoimmune hypothyroidism (16% with goiter, 84% with no thyroid visible or palpable). In conclusion, in an area with moderately low iodine intake, hypothyroidism was considerably less common than hyperthyroidism. This is in contrast to findings in high iodine intake areas. The iodine intake of an area seems to be of major importance for the pattern of thyroid disorders observed.

The epidemiology of thyroid disease and implications for screening

The burden of thyroid disease in the general population is enormous. As many as 50% of people in the community have microscopic nodules, 3.5% have occult papillary carcinoma, 15% have palpable goiters, 10% demonstrate an abnormal thyroid-stimulating hormone level, and 5% of women have overt hypothyroidism or hyperthyroidism. Despite this high prevalence of thyroid disease, screening for these disorders is not recommended by any major health agency. This article explores the epidemiologic issues surrounding this complex problem by analyzing prevalence, incidence, and mortality data from a worldwide variety of sources.

The many causes of subclinical hyperthyroidism

Subclinical hyperthyroidism, defined as serum thyroid hormone levels in the reference range with low serum TSH concentration, is a well recognized clinical entity, but little information is available concerning the prevalence of the disorders that produce it. We conducted a 24-month retrospective survey of subclinical hyperthyroidism patients referred to a university hospital nuclear medicine service for diagnostic studies. Twenty-four consecutive patients were evaluated (22 outpatients and 2 inpatients). All patients had highly sensitive TSH determination, thyroid hormone levels, radioiodine uptake and scan (except for 2 postpartum women), and, selectively, TSH-receptor antibody (TRAb), serum thyroglobulin, antithyroid antibodies, T3-suppression test, and erythrocyte sedimentation rate. A TSH value of about 0.1 microIU/mL was used as the cutoff. Only one patient in the group had a nonthyroidal disorder. In 14 patients (61%) subclinical hyperthyroidism was self-limited, due to silent thyroiditis (5 patients), iodine-induced hyperthyroidism (3 patients), postpartum thyroiditis (2 patients), subacute thyroiditis (2 patients), and probable hemorrhage into a functioning nodule (2 patients). Of the non-self-limited disorders (39%), Graves' disease accounted for 6 patients and solitary or multinodular goiter for 3. Graves' disease proved difficult to diagnose because the thyroid gland was normal in size in two of the six patients, TRAb was positive in only two of six, and the radioiodine uptake and gradient were normal in all six; the T3-suppression test was positive in two of two patients. We conclude that the causes of subclinical hyperthyroidism are the disorders that commonly produce overt thyrotoxicosis in medical practice, Graves' disease being the most frequent. However, the tests used to diagnose overt Graves' disease often fail in the setting of subclinical hyperthyroidism, except possibly the T3-suppression test.

The incidence of thyroid disorders in the community: a twenty-year follow-up of the Whickham Survey

BACKGROUND AND OBJECTIVE

The original Whickham Survey documented the prevalence of thyroid disorders in a randomly selected sample of 2779 adults which matched the population of Great Britain in age, sex and social class. The aim of the twenty-year follow-up survey was to determine the incidence and natural history of thyroid disease in this cohort.

DESIGN, PATIENTS AND MEASUREMENTS

Subjects were traced at follow-up via the Electoral Register, General Practice registers, Gateshead Family Health Services Authority register and Office of Population Censuses and Surveys. Eight hundred and twenty-five subjects (30% of the sample) had died and, in addition to death certificates, two-thirds had information from either hospital/General Practitioner notes or post-mortem reports to document morbidity prior to death. Of the 1877 known survivors, 96% participated in the follow-up study and 91% were tested for clinical, biochemical and immunological evidence of thyroid dysfunction.

RESULTS

Outcomes in terms of morbidity and mortality were determined for over 97% of the original sample. The mean incidence (with 95% confidence intervals) of spontaneous hypothyroidism in women was 3.5/1000 survivors/year (2.8-4.5) rising to 4.1/1000 survivors/year (3.3-5.0) for all causes of hypothyroidism and in men was 0.6/1000 survivors/year (0.3-1.2). The mean incidence of hyperthyroidism in women was 0.8/1000 survivors/year (0.5-1.4) and was negligible in men. Similar incidence rates were calculated for the deceased subjects. An estimate of the probability of the development of hypothyroidism and hyperthyroidism at a particular time, i.e. the hazard rate, showed an increase with age in hypothyroidism but no age relation in hyperthyroidism. The frequency of goitre decreased with age with 10% of women and 2% of men having a goitre at follow-up, as compared to 23% and 5% in the same subjects respectively at the first survey. The presence of a goitre at either survey was not associated with any clinical or biochemical evidence of thyroid dysfunction. In women, an association was found between the development of a goitre and thyroid-antibody status at follow-up, but not initially. The risk of having developed hypothyroidism at follow-up was examined with respect to risk factors identified at first survey. The odds ratios (with 95% confidence intervals) of developing hypothyroidism with (a) raised serum TSH alone were 8 (3-20) for women and 44 (19-104) for men; (b) positive anti-thyroid antibodies alone were 8 (5-15) for women and 25 (10-63) for men; (c) both raised serum TSH and positive anti-thyroid antibodies were 38 (22-65) for women and 173 (81-370) for men. A logit model indicated that increasing values of serum TSH above 2mU/l at first survey increased the probability of developing hypothyroidism which was further increased in the presence of anti-thyroid antibodies. Neither a positive family history of any form of thyroid disease nor parity of women at first survey was associated with increased risk of developing hypothyroidism. Fasting cholesterol and triglyceride levels at first survey when corrected for age showed no association with the development of hypothyroidism in women.

CONCLUSIONS

This historical cohort study has provided incidence data for thyroid disease over a twenty-year period for a representative cross-sectional sample of the population, and has allowed the determination of the importance of prognostic risk factors for thyroid disease identified twenty years earlier.

Should thyroid function be assessed before cardiopulmonary bypass operations?

Thyroid function is depressed during and after cardiopulmonary bypass surgical procedures, and this may adversely affect myocardial performance. There is known to be a high prevalence of thyroid abnormalities in the elderly population, and many patients undergoing cardiac operations fall into this category. We have assessed thyroid function in 116 patients admitted for elective open heart procedures to determine the value of preoperative testing. Abnormalities in thyroid function were present in 13 (11.2%) of the patients studied, 3 of whom were receiving thyroxine therapy. One patient who had overt hypothyroidism died postoperatively of a large cerebral infarct; 11 had elevated thyrotropin levels with normal serum thyroxine levels; and 1 who had overtreated hypothyroidism suffered fast atrial fibrillation postoperatively. No other complications were observed. These findings indicate that thyroid function should be assessed preoperatively in patients already on thyroxine therapy. Whether thyroid function should be evaluated routinely in all patients before operations involving cardiopulmonary bypass is not clear. Although there is a high incidence of abnormal laboratory results, there were no apparent adverse effects on the surgical outcome.

The importance of thyroid microsomal antibodies in the development of elevated serum TSH in middle-aged women: associations with serum lipids

OBJECTIVE

We assessed the relative risk of both serum TSH and antithyroid antibody concentrations with regard to progression of thyroid failure and studied the lipid profiles of individuals with elevated TSH levels.

DESIGN, PATIENTS AND MEASUREMENTS

In a randomly selected group of 427 women aged 40-60 (mean 55) years volunteering in an epidemiological survey in Zoetermeer, TSH and thyroid microsomal antibodies (TMA) were determined. Ten years after the initial survey only TSH was measured and the lipid profiles of the individuals with elevated serum TSH levels were studied and compared with a reference group.

RESULTS

During follow-up, four of 427 women were treated with thyroxine. Seventeen of 423 women initially had elevated serum concentrations of TSH (> 4.2 mU/l), 11 of whom were TMA positive. In the group of 406 women with initially a normal TSH, nine out of 37 (24%) TMA-positive women developed elevated serum levels of TSH over 10 years. In contrast only 10 of 369 (3%) TMA-negative women had elevated serum TSH levels 10 years after the initial survey (P < 0.001). Altogether, at the end of the observation period, 40% of TMA-positive subjects had elevated serum TSH concentrations, compared to 3% in the TMA-negative group (P < 0.01). TSH levels in the upper part of the normal range also appeared to have a predictive value: if those both with TSH levels between 2.0 and 4.2 and with a positive TMA status were contrasted with those without antibodies and low TSH, the crude relative risk was 71.5 (31.0-164.3), whereas the crude relative risk of presence versus absence of TMA was only 36.3 (18.8-70.3). Women with elevated TSH levels did not show changes in serum concentrations of total cholesterol (7.4 +/- 1.1 mmol/l), apo-A, (4.7 +/- 1.0 mmol/l) and apo-B (3.1 +/- 0.7 mmol/l) lipoproteins, compared with control individuals (7.2 +/- 1.3, 4.7 +/- 0.8 and 3.0 +/- 0.7 mmol/l, respectively).

CONCLUSIONS

The determination of serum TMA in middle-aged women can identify an important group of women at risk of developing an elevated serum TSH. TMA measurement is of potential use in the prevention of cardiovascular disease. An elevated serum TSH, however, in our study-group does not seem to be accompanied by an abnormal lipid profile, as reported by others.

Factors affecting the serum free thyroxine levels in hospitalized chronic geriatric patients

OBJECTIVE

Determination of whether nonthyroidal factors affect the diagnostic value of free thyroxine estimation in geriatric patients.

DESIGN

Survey.

PARTICIPANTS

A convenience sample of 381 non-selected, chronic, hospitalized geriatric patients over 60 years of age (I = relatively good health; II = relatively poor health; III = bad health; subgroups "sine therapia," ie, patients receiving no drugs that affect FT4) and 180 20-40 year old healthy persons.

MEASUREMENTS

Thyrotropin-releasing hormone test; thyrotropin (TSH); free thyroxine (FT4, measured in part by two parallel methods) estimation in a screening study; and thyroxine-binding globulin and thyroxine-binding-inhibitor activity measurements.

RESULTS

The normal FT4 ranges of the euthyroid geriatric (n = 210) and healthy young groups were similar. In the "sine therapia" euthyroid patients, FT4 decreased with age but increase with the severity of illness. High FT4 levels with non-suppressed TSH were more frequent in patients in poor and bad health. (I = 6/112; II = 14/140; III = 13/74; P < 0.01). The serum thyroxine-binding-inhibitor activity of euthyroid geriatric patients correlated with the severity of their clinical state (I = 6.22 +/- 5.65 (13); II = 7.40 +/- 4.33 (23); III = 10.04 +/- 5.50 (16) micrograms merthiolate equivalent/microL; ANOVA with log-transformed values: F(2.51) = 3.50, P < 0.05). The mean FT4 was higher in 36 heparin-treated patients (22.81 +/- 4.67 pmol/L) than in the 193 "sine therapia" patients (19.03 +/- 4.23 pmol/L; -P < 0.001). In a convenience subsample of 240 patients, a weak inverse correlation was found between FT4 and the thyroxine-binding globulin (r = -0.14, P < 0.02). Only 5/11 patients with low free thyroxine had hypothyroidism, while 11/46 patients with elevated free thyroxine had hyperthyroidism.

CONCLUSIONS

There is no need to modify the normal free thyroxine range for hospitalized geriatric patients. Clinical condition, drug treatment, and, to a lesser extent, age are factors that significantly affect the diagnostic value of FT4 in hospitalized chronic geriatric patients, decreasing the specificity of the test in diagnosing clinical hyper- and hypothyroidism.

Self-reported versus actual test ordering behavior among primary care clinicians

To determine the accuracy of clinician self-reports, 38 clinicians were surveyed in a university-based health maintenance organization (HMO) practice on their thyroid function testing (TFT) patterns one year after the distribution of an educational intervention (the intervention). The mean of the absolute difference between self-reported and actual test ordering rates was 12%; the difference was greater than 20% for only 3 of 33 clinicians who ordered TFT for at least five patients during the study period. A strong association was found between self-reported change and the actual mean change in TFT postintervention ordering rates (p less than 0.0001). Results suggest that clinicians, at least in certain settings, can accurately estimate their utilization patterns and the effect of practice guidelines.

Prevalence and follow-up of abnormal thyrotrophin (TSH) concentrations in the elderly in the United Kingdom

Increasing use of assays for TSH with improved sensitivity as a first-line test of thyroid function has raised questions regarding prevalence and clinical significance of abnormal results, especially values below normal. We have assessed the thyroid status of 1210 patients aged over 60 registered with a single general practice by measurement of serum TSH using a sensitive assay. High TSH values were more common in females (11.6%) than males (2.9%). TSH values below normal were present in 6.3% of females and 5.5% of males, with values below the limit of detection of the assay present in 1.5% of females and 1.4% of males. Anti-thyroid antibodies were found in 60% of those with high TSH but only 5.6% of those with subnormal TSH. Eighteen patients were hypothyroid (high TSH, low free thyroxine) and one thyrotoxic (low TSH, raised free thyroxine) at initial testing. Seventy-three patients with elevated TSH but normal free T4 were followed for 12 months; 13 (17.8%) developed low free T4 levels and commenced thyroxine, TSH returned to normal in four (5.5%) and 56 (76.7%) continued to have high TSH values. Sixty-six patients with TSH results below normal were followed. Of the 50 subjects with low but detectable TSH at initial testing, 38 (76%) returned to normal at 12 months; of those 16 with undetectable TSH followed, 14 (87.5%) remained low at 12 months. Only one subject (who had an undetectable TSH) developed thyrotoxicosis. In view of the marked prevalence of thyroid dysfunction in the elderly, we suggest that screening of all patients over 60 should be considered.(ABSTRACT TRUNCATED AT 250 WORDS)