Prevalence of subclinical thyroid dysfunction and its relation to socioeconomic deprivation in the elderly: a community-based cross-sectional survey

CONTEXT: Population-based screening has been advocated for subclinical thyroid dysfunction in the elderly because the disorder is perceived to be common, and health benefits may be accrued by detection and treatment. OBJECTIVE: The objective of the study was to determine the prevalence of subclinical thyroid dysfunction and unidentified overt thyroid dysfunction in an elderly population. DESIGN, SETTING, AND PARTICIPANTS: A cross-sectional survey of a community sample of participants aged 65 yr and older registered with 20 family practices in the United Kingdom. EXCLUSIONS: Exclusions included current therapy for thyroid disease, thyroid surgery, or treatment within 12 months. OUTCOME MEASURE: Tests of thyroid function (TSH concentration and free T4 concentration in all, with measurement of free T3 in those with low TSH) were conducted. EXPLANATORY VARIABLES: These included all current medical diagnoses and drug therapies, age, gender, and socioeconomic deprivation (Index of Multiple Deprivation, 2004). ANALYSIS: Standardized prevalence rates were analyzed. Logistic regression modeling was used to determine factors associated with the presence of subclinical thyroid dysfunction. RESULTS: A total of 5960 attended for screening. Using biochemical definitions, 94.2% [95% confidence interval (CI) 93.8-94.6%] were euthyroid. Unidentified overt hyper- and hypothyroidism were uncommon (0.3, 0.4%, respectively). Subclinical hyperthyroidism and hypothyroidism were identified with similar frequency (2.1%, 95% CI 1.8-2.3%; 2.9%, 95% CI 2.6-3.1%, respectively). Subclinical thyroid dysfunction was more common in females (P < 0.001) and with increasing age (P < 0.001). After allowing for comorbidities, concurrent drug therapies, age, and gender, an association between subclinical hyperthyroidism and a composite measure of socioeconomic deprivation remained. CONCLUSIONS: Undiagnosed overt thyroid dysfunction is uncommon. The prevalence of subclinical thyroid dysfunction is 5%. We have, for the first time, identified an independent association between the prevalence of subclinical thyroid dysfunction and deprivation that cannot be explained solely by the greater burden of chronic disease and/or consequent drug therapies in the deprived population.     

La thyroïde de la personne âgée (partie 2)

Aging is associated with an increased prevalence of thyroid diseases. The diagnosis of overt hypothyroidism and hyperthyroidism may be difficult since they are often pauci- or monosymptomatic. Subclinical forms of thyroid diseases, in particular hypothyroidism, are even more frequent. Therapeutic abstention with regular follow-up is usually recommended in hypothyroidism. Radical treatment is usually preferred for subclinical hyperthyroidism since heart complications may be severe. Increased prevalence of benign and malignant nodules is observed in the elderly. The prognosis of thyroid cancer is less favorable than in adults, due to a higher proportion of histological types with a worse evolution. Whatever the thyroid disease, diagnosis and treatment modalities should be adapted to the age and general conditions of the patient. Contradictory results have been reported on the relationship between thyroid status and neuromuscular and cognitive alterations linked to aging.     

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.     

Subclinical thyroid dysfunction in the elderly.

Subclinical thyroid dysfunction is more common in older persons. By definition, these disorders are recognized by isolated elevation or suppression of the serum TSH concentration, in association with a normal serum free thyroxine level. Among individuals over 65 years old, subclinical hypothyroidism is found in approximately 10% of women and approximately 3% of men. It is most commonly due to autoimmune thyroiditis or previous treatment for hyperthyroidism. There may be three indications for L-thyroxine therapy: (a) presence of antithyroid antibodies, indicating substantial risk of progression to over hypothyroidism; (b) symptoms consistent with thyroid hormone deficiency; and (c) an elevated serum LDL-cholesterol. Subclinical hyperthyroidism is present in approximately 1%-2% of older persons. The most common cause is excessive thyroid hormone therapy, followed by mild endogenous hyperthyroidism due to Graves' disease or nodular goiter. These can be differentiated from other causes of low serum TSH concentration based on clinical and other laboratory and radionuclide scan criteria. The most serious consequences of subclinical hyperthyroidism are atrial fibrillation and osteoporosis, to which elderly patients are particularly predisposed.     

Subclinical thyroid dysfunction and blood pressure: a community-based study

OBJECTIVE: Overt hypothyroidism and hyperthyroidism are associated with hypertension, but it is uncertain whether the same is true of subclinical hypothyroidism and hyperthyroidism. DESIGN, SUBJECTS AND MEASUREMENTS: Cross-sectional study of 2033 participants (aged 17-89 years) in the Busselton Thyroid Study who did not have a history of thyroid disease. Systolic blood pressure (SBP), diastolic blood pressure (DBP) and the prevalence of hypertension (defined as SBP >or=140 mmHg, DBP >or=90 mmHg or on treatment for hypertension) in subjects with thyroid dysfunction and euthyroid subjects were compared using linear regression models. Subjects with treated hypertension (N = 299) were excluded from analyses of SBP and DBP but included in analyses of hypertension prevalence. RESULTS: Mean SBP, DBP and the prevalence of hypertension did not differ significantly between subjects with subclinical hypothyroidism (N = 105) and euthyroid subjects (N = 1859), nor did they differ between subjects with serum TSH concentrations in the upper reference range (2.0-4.0 mU/l; N = 418) and those with TSH concentrations in the lower reference range (0.4-2.0 mU/l; N = 1441). The prevalence of hypertension was higher in subjects with subclinical hyperthyroidism than euthyroid subjects (prevalence odds ratio 2.8, 95% confidence interval 1.3-6.0 adjusted for age, age(2) and sex), but this was based on a small number of subjects with subclinical hyperthyroidism (N = 35). CONCLUSIONS: Subclinical hypothyroidism is not associated with hypertension. The observed association between subclinical hyperthyroidism and hypertension requires confirmation in a larger sample.     

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

The use of a screening test for thyroid functional disorder by sensitive thyroid stimulating hormone assay in the elderly was investigated. The basal thyroid stimulating hormone levels predicted the response of thyroid stimulating hormone to thyrotropin releasing hormone; it was suppressed in 99 (99.0%) of 100 hyperthyroid patients. Therefore, not only primary hypothyroidism but also hyperthyroidism can be excluded when the serum thyroid stimulating hormone levels are normal. An epidemiological study was then performed on 2,421 (76.7%) of the Japanese general population aged 40 or over recruited from the residents in Hisayama town and also in 122 residents between 20 and 40 years of age. Additional free T4 measurement was necessary in about 10% of the residents with abnormal TSH levels to confirm the diagnosis of hyperthyroidism or distinguish latent from overt hypothyroidism. There was a significant correlation between age and serum thyroid stimulating hormone levels after logarithmic conversion (r = 0.1533, P less than .001). The prevalence of thyroid dysfunction found in 1,026 males and in 1,395 females aged 40 or over was, respectively: hyperthyroidism, less than 0.1% and 0.2%, latent (subclinical) hypothyroidism, 3.2% and 5.5%, and overt hypothyroidism, 0.4% and 0.7%. We conclude that the screening with this sensitive thyroid stimulating hormone assay and additional free T4 measurement is useful for detection of patients with thyroid functional disorder.     

Subclinical thyroid disease

Subclinical thyroid diseases--subclinical hyperthyroidism and subclinical hypothyroidism--are common clinical entities that encompass mild degrees of thyroid dysfunction. The clinical significance of mild thyroid overactivity and underactivity is uncertain, which has led to controversy over the appropriateness of diagnostic testing and possible treatment. In this Seminar, we discuss the definition, epidemiology, differential diagnoses, risks of progression to overt thyroid disease, potential effects on various health outcomes, and management of subclinical hyperthyroidism and subclinical hypothyroidism. Treatment recommendations are based on the degree to which thyroid-stimulating hormone concentrations have deviated from normal and underlying comorbidities. Large-scale randomised trials are urgently needed to inform how to best care for individuals with subclinical thyroid disease.     

Socio demographic wise risk assessment of thyroid function abnormalities in far western region of Nepal: A hospital based descriptive study

Objective

To know the status of thyroid disorder in population of far western region of Nepal.

Methods

A total of 808 cases (133 men and 675 non pregnant women) were included and study was carried out using data retrieved from the register maintained in the Department of Biochemistry of the Nepalgunj Teaching Hospital between 1st January, 2011 and 28th February, 2012. The variables collected were age, sex, and thyroid function profile including free T3, free T4 and TSH.

Results

The percentage of thyroid disorders was 33.66% in far western region of Nepal. The people were highly affected by overt hyperthyroidism (14.9%) followed by subclinical hyperthyroidism (9.9%). The subclinical hypothyroidism was 7.9% while 1% overt hypothyroidism only in a far western region of Nepal. Females were highly affected by overt hyperthyroidism (17.8%), followed by subclinical hyperthyroidism (11.9%). A total of 5.9% females were affected by subclinical hypothyroidism while only 1.2% by overt hypothyroidism. Males were affected only by subclinical hypothyroidism (18.0%) in this present study. High number of total thyroid dysfunction was observed in 21 to 40 years of age groups, followed by 41 to 60 years of age groups. Less than 40 years people were having 1.03, 0.99, 2.51 and 1.15 times risk of developing overt hyperthyroidism, subclinical hyperthyroidism, overt hypothyroidism and subclinical hyperthyroidism respectively compared to greater than 40. Female were having 0.29 times risk of developing subclinical hyperthyroidism compared to male. But overt hyperthyroidism, subclinical hyperthyroidism and overt hypothyroidism female were having more risk of developing compared to male.

Conclusions

The thyroid disorder, especially overt hyperthyroidism (14.9%) and subclinical hyperthyroidism (9.9%) was high. Further studies are required to characterize the reasons for this high prevalence.     

The prevalence of undiagnosed thyroid disorders in a previously iodine-deficient area.

OBJECTIVE: The aim of the present study was to analyze the current status of morphologic and functional thyroid abnormalities in a previously iodine-deficient area. METHODS: The population based Study of Health in Pomerania (SHIP) comprised 4310 participants, aged 20-79 years. Thyroid function (thyrotropin [TSH] free triiodothyronine [FT(3)], and free thyroxine [FT(4)]) and serum autoantibodies to thyroperoxidase (TPOAb) were evaluated from blood samples. Thyroid structure and size were measured by ultrasound. Data from 3941 participants with no known thyroid disorders were analyzed. RESULTS: The median iodine urine excretion was 12.4 microg/dL. The rate of decreased serum TSH levels (<0.3 mIU/L) was 11.3%; 2.2% of participants had suppressed serum TSH levels (<0.1 mIU/L). The prevalence of subclinical hyperthyroidism was 1.8%, the prevalence of overt hyperthyroidism 0.4%. Elevated TSH levels were found in 1.2% of individuals. Subclinical hypothyroidism was observed in 0.5%, overt hypothyroidism in 0.7% of the sample. Elevated TPOAb were detected in 7% of subjects, 4.1% of participants had TPOAb greater than 200 IU/mL. The prevalence of goiter was 35.9%. An inhomogeneous echo pattern was detected in 35.2% and nodules in 20.2% of participants. Diffuse autoimmune thyroiditis was diagnosed in 47 subjects (1.2%). CONCLUSION: There are a number of thyroid disorders in this previously iodine-deficient region. Further studies are required to investigate the change of thyroid disorders during iodine supplementation programs.     

No association between HIV disease and its treatment and thyroid function

OBJECTIVES: The aims of the study were (i) to investigate the prevalence of overt and subclinical thyroid disease in HIV-positive patients in a London teaching hospital; (ii) to determine risk factors associated with the development of thyroid dysfunction, including highly active antiretroviral therapy (HAART) and individual antivirals, and (iii) to determine the occurrence of thyroid dysfunction longitudinally over 3 years. METHODS: The study consisted of retrospective analyses of thyroid function tests (TFT) in HIV-positive patients. The period prevalence of and factors associated with clinical and subclinical thyroid dysfunction were investigated. Patients with normal TFT but previous thyroid disease were identified from pharmacy records and included in the overt category. RESULTS: A total of 1565 patients (73% of the clinic population) had at least one TFT taken since 2001. Overall, 3584 samples were analysed. Of the patients included in the study, 1233 (79%) were male, 1043 (66%) were white and 365 (23%) were black African, and in 969 (62%) the main risk for HIV was homosexual sex. Median age at baseline was 37 years. Nine hundred patients (58%) were on HAART at the start of the study. Thirty-nine (2.5%) were found to have overt hypothyroidism, and eight (<1%) had overt hyperthyroidism. Sixty-one (4%) had subclinical hypothyroidism, five (<1%) had subclinical hyperthyroidism and 263 (17%) had a nonthyroidal illness. A normal TFT was obtained for 1118 patients (75.5%). Multivariate analysis suggested that no independent variables were significantly associated with overt hypothyroidism, including HAART and stavudine use specifically. Repeated measurements over 3 years were available for 825 patients and only eight new cases (1%) of overt thyroid disease occurred. CONCLUSIONS: The prevalence of overt thyroid disease was low in this cohort, suggesting that screening is not warranted.     

A clinical and therapeutic approach to thyrotoxicosis with thyroid-stimulating hormone suppression only

Subclinical hyperthyroidism is defined as normal serum free thyroxine (T4) and triiodothyronine (T3) concentrations and persistently suppressed thyroid stimulating hormone (TSH) concentrations. The most common cause of subclinical hyperthyroidism is the use of suppressive doses of L-thyroxine for treatment of hypothyroidism or, less commonly, diffuse nontoxic goiter or thyroid carcinoma (exogenous subclinical hyperthyroidism). Endogenous subclinical hyperthyroidism may be caused by a variety of thyroid disorders that result in overproduction and release of thyroid hormones from the gland with normal/high 24-hour thyroid radioiodine uptake or by inflammation in the thyroid resulting in release of excess thyroid hormones and low 24-hour thyroid radioiodine uptake. Several groups have investigated whether persistent endogenous or exogenous subclinical hyperthyroidism, like overt hyperthyroidism, causes symptoms, adverse effects on the cardiovascular and the skeletal systems, and increased mortality, whether endogenous subclinical hyperthyroidism evolves to overt thyrotoxicosis, and whether or not it should be treated. The present report reviews the most important and recent studies of subclinical hyperthyroidism and attempts to draw conclusions based upon the literature and the authors' experience.     

Subclinical hyperthyroidism.

Subclinical hyperthyroidism is defined as a situation where the levels of the peripheral thyroid hormones are normal but serum thyrotropin (TSH) is low. It is not a rare finding; rates between 0.2% and 11.8% have been reported in different groups, according to age, sex, etc. The etiology is usually the same as that of overt hyperthyroidism. The health implications include general symptoms, effects on the cardiovascular system, and decreased bone density. The increased frequency of atrial fibrillation and the increased mortality reported are especially serious. It is not clear whether subclinical hyperthyroidism should be treated or not. Most authors conclude that treatment is required in selected cases or in special circumstances.     

Thoughts on prevention of thyroid disease in the United States.

In the realm of preventive medicine, there are three distinct types of prevention that can be defined. Primary prevention is the prevention of new disease in previously healthy individuals, usually achieved by decreasing risk factors for disease. Secondary prevention is the prevention of progression of mild or latent disease to more severe disease, and typically involves screening for occult disease. Tertiary prevention is the term used by some to describe medical care intended to improve already established disease. The role of primary prevention of thyroid disease in the United States is uncertain, because iodine deficiency is not clearly known to be a problem. In the case of secondary prevention of thyroid disease, this would necessarily involve screening of individuals for subclinical hyperthyroidism or hypothyroidism with thyrotropin (TSH) testing. Using data from a large prevalence study and from the 2000 U.S. Census, it can be calculated that approximately 15 million adults have unrecognized thyroid disease, mostly subclinical hypothyroidism. If detected, secondary prevention might also entail treatment with antithyroid drugs/radioiodine or thyroxine to prevent sequelae or progression to a more advanced degree of thyrotoxicosis or thyroid failure, respectively. Over the next 20 years, it can be calculated that approximately 5 million people, mostly with subclinical hypothyroidism, will progress to overt disease. Tertiary prevention of thyroid disease would involve avoiding iatrogenic disease, such as thyroid hormone overdose. From epidemiologic data it can be calculated that approximately 600,00 elderly individuals have iatrogenic hyperthyroidism from thyroid hormone overdose, putting them at risk for atrial fibrillation and osteoporosis. Together, these data suggest that the notion of preventive medicine in the United States should be expanded to include thyroid disease as a target for secondary and tertiary intervention.     

Subclinical hypothyroidism: the state of the art

Subclinical hypothyroidism (SH) is a common clinical problem, particularly in adulthood and the elderly. Its prevalence is conditioned by several etiological and risk factors. The highest age- and sex-specific rates are in women over 60. SH may be associated with manifestations of mild thyroid failure, which may reverse under levothyroxine (L-T4) therapy. The risk of progression to overt hypothyroidism is distinctly higher in cases with underlying thyroid disease. A population routine screening is not generally recommended, but screening is encouraged in high-risk groups. L-T4 therapy may be indicated in subjects with TSH levels which are repeatedly and consistently elevated (>10 microIU/ml) and may be considered in those with TSH ranging between 4.5-5.5 and 10 microIU/ml, particularly if anti-thyroid antibodies are positive and/or hypothyroid symptoms are present. Treatment should be based, at least initially, on L-T4 low doses.     

Thyroid Function Abnormalities and Cognitive Impairment in Elderly People: Results of the Invecchiare in Chianti Study

OBJECTIVES: To investigate thyroid function testing abnormalities in older persons and to explore the relationship between thyroid dysfunction and cognition.
DESIGN: Cross-sectional.
SETTING: Community-based.
PARTICIPANTS: One thousand one hundred seventy-one men and women aged 23 to 102.
MEASUREMENTS: Thyroid function was evaluated by measuring plasma concentrations of thyrotropin (TSH), free thyroxine (FT4), and free triiodothyronine (FT3). Cognition was evaluated using the Mini-Mental State Examination (MMSE). Prevalence of overt and subclinical thyroid dysfunction was evaluated in different age groups (<65 vs ≥65). Age trends in TSH, FT4, and FT3 were examined in euthyroid participants. The cross-sectional association between thyroid dysfunction and MMSE score was evaluated adjusting for confounders.
RESULTS: Subclinical hypothyroidism and subclinical hyperthyroidism were more prevalent in older than in younger participants (subclinical hypothyroidism, 3.5% vs 0.4%, P <.03; subclinical hyperthyroidism, 7.8% vs 1.9%, P <.002). In euthyroid participants, TSH and FT3 declined with age, whereas FT4 increased. Older participants with subclinical hyperthyroidism had lower MMSE scores than euthyroid subjects (22.61±6.88 vs 24.72±4.52, P <.03). In adjusted analyses, participants with subclinical hyperthyroidism were significantly more likely to have cognitive dysfunction (hazard rate=2.26, P =.003).
CONCLUSION: Subtle age-related changes in FT3, FT4, and TSH occur in individuals who remain euthyroid. Subclinical hyperthyroidism is the most prevalent thyroid dysfunction in Italian older persons and is associated with cognitive impairment.     

The clinical significance of subclinical thyroid dysfunction

Subclinical thyroid disease (SCTD) is defined as serum free T(4) and free T(3) levels within their respective reference ranges in the presence of abnormal serum TSH levels. SCTD is being diagnosed more frequently in clinical practice in young and middle-aged people as well as in the elderly. However, the clinical significance of subclinical thyroid dysfunction is much debated. Subclinical hyper- and hypothyroidism can have repercussions on the cardiovascular system and bone, as well as on other organs and systems. However, the treatment and management of SCTD and population screening are controversial despite the potential risk of progression to overt disease, and there is no consensus on the thyroid hormone and thyrotropin cutoff values at which treatment should be contemplated. Opinions differ regarding tissue effects, symptoms, signs, and cardiovascular risk. Here, we critically review the data on the prevalence and progression of SCTD, its tissue effects, and its prognostic implications. We also examine the mechanisms underlying tissue alterations in SCTD and the effects of replacement therapy on progression and tissue parameters. Lastly, we address the issue of the need to treat slight thyroid hormone deficiency or excess in relation to the patient's age.     

Epidemiology and prevention of Graves' ophthalmopathy.

Graves' ophthalmopathy is clinically relevant in approximately 50% of patients with Graves' disease, severe forms affecting 3%-5% of patients. Two age peaks of incidence are observed in the fifth and seventh decades of life, with slight differences between women and men. The disease is more frequent in women than in men, although the female-to-male ratio is only 1:4 in severe forms of eye disease. The natural history of Graves' ophthalmopathy is incompletely defined, but in many instances, especially in mild forms, the disease may remit or improve spontaneously. The onset of the ophthalmopathy is in most cases concomitant with the onset of hyperthyroidism, but eye disease may precede or follow hyperthyroidism. Cigarette smoking plays an important role in the occurrence of the ophthalmopathy, and is also associated with a higher degree of disease severity and a lower effectiveness of its medical treatment. Primary prevention (i.e., avoidance of the occurrence of the ophthalmopathy) is presently not feasible, but smoking withdrawal in relatives of patients with Graves' disease might be important. In terms of secondary prevention (i.e., avoidance of progression of subclinical eye disease into overt and severe ophthalmopathy) in addition to refraining from smoking, early and accurate control of thyroid dysfunction (both hyperthyroidism and hypothyroidism), as well as early diagnosis and treatment of mild eye disease are important. As to the role that management of hyperthyroidism may play in the course of Graves' ophthalmopathy, while antithyroid drugs and thyroidectomy are not disease-modifying treatments, radioiodine therapy causes a progression of the ophthalmopathy in approximately 15% of patients, especially high-risk patients, who smoke, have severe hyperthyroidism or uncontrolled hypothyroidism, high levels of thyrotropin (TSH)-receptor antibody, or preexisting eye disease. However, the risk of radioiodine-associated progression of the opthalmopathy can be eliminated by concomitant treatment with middle-dose glucocorticoids. In terms of tertiary prevention (i.e., avoidance of deterioration and complications of overt disease) early immunosuppressive treatment or orbital decompression, as appropriate, are essential tools. Smoking withdrawal may increase the effectiveness of immunosuppressive treatment.     

Mortality rate of chronically ill geriatric patients with subnormal serum thyrotropin concentration: a 2-yr follow-up study

We investigated the natural course of subclinical thyroid dysfunctions in geriatric patients, especially regarding their association with mortality rate. Ninety-three randomly selected chronically ill geriatric patients 64–87 (median: 77) yr of age participated in the screening study with a 2-yr follow-up. Serum thyrotropin (thyroid-stimulating hormone [TSH]), free thyroxine, triiodothyronine, and antibodies against thyroid peroxidase were measured. During the follow-up, patients with suppressed TSH levels who were otherwise euthyroid (untreated) had a higher mortality rate than patients with normal TSH (5/8 vs 18/64; p<0.05). The initial clinical state of these two subgroups did not differ significantly. Two-thirds of patients with treated hyperthyroidism died. The mortality rate of patients with initially subnormal but not suppressed TSH level was average and did not differ statistically from either the euthyroid or the hyperthyroid groups. Only 1 of 13 euthyroid patients with positive thyroid antibody titers developed a subsequent subclinical hypothyroidism. Subclinical hyperthyroidism was found to be associated with a higher mortality rate in chronically ill geriatric patients, which justifies screening for thyroid dysfunction and treatment of subclinical hyperthyroidism. In addition, a subnormal but measurable TSH was not indicative regarding the future development of hyperthyroidism. Finally, during the 2-yr follow-up, antibody positivity in the euthyroid cases did not prove to be predictive for the subsequent development of hypothyroidism.     

Amiodarone-induced thyroid dysfunction in a tertiary center in south Brazil

Amiodarone, used in the treatment of cardiac arrhythmias, is associated with thyroid dysfunction. No reports exist on its frequency in southern Brazil, nor studies evaluating the usefulness of clinical scores to diagnose thyroid abnormalities in these patients. This study aimed at determining the prevalence of amiodarone-induced thyroid dysfunction in a representative sample from a tertiary center, to study the conditions associated to this dysfunction and to evaluate the reliability of clinical scores of hypo and hyperthyroidism. One hundred ninety-five amiodarone users were submitted to a clinical and laboratory evaluation. Of these, 2.1% were hyperthyroid, 25.1% hypothyroid and 9.2% had only a high T4. Considering thyroid dysfunction variables researched, thyroid autoimmunity was positively associated (OR 4.8; p= 0.02), and male gender had a trend to a positive association (OR 1.86; p= 0.06). Clinical scores were highly sensitive for hyperthyroidism (100%), but not for hypothyroidism (8%). The low prevalence of amiodarone-induced hypothyroidism suggests that this specific region is iodine-sufficient. All patients receiving chronic amiodarone therapy should be checked for clinical scores for hyperthyroidism and laboratory evaluation should be performed, as a screening for thyroid dysfunction, especially if they are male or have positive microsomal antibodies.