The change in the clinical presentation of Graves' disease: a 30 years retrospective survey in an academic Brazilian tertiary center.

OBJECTIVE: Graves' disease (GD) is the main cause of hyperthyroidism among adults. It is an autoimmune condition classically marked by the Merserburg Triad (goiter, thyrotoxicosis, and orbitopathy), but the change in presentation of GD over time has rarely been studied. To determine changes in the clinical presentation of patients with GD in the last 30 years. METHODS: The study evaluated 475 patients diagnosed with GD between 1986 and 2016 in a single center. Patients were evaluated regarding epidemiological aspects, thyroid function, inflammatory activity of the eyes evaluated by the Clinical Activity Score; CAS, severity evaluated by NOSPECS classification and thyroid volume estimated by ultrasonography. RESULTS: Patients assessment identified an increase in the mean age of diagnosis of GD (p < 0.02), a reduction in thyroid volume (p < 0.001) and less intense orbital involvement from 2007-2016 compared to 1986-2006 (p = 0.04). The number of smoking patients was smaller from 2007 to 2016 (28.7%) than 1986 to 2006 (42.8% p = 0.001). The TSH and TRAb values did not had significant changes. CONCLUSION: GD presentation appears to be changed in the last years compared to the typical initial presentation. There is a less frequent inflammatory involvement of orbital tissue, smaller goiters, a lower number of smokers and diagnosis at older age.

The polymorphic inheritance of DIO2 rs225014 may predict body weight variation after Graves' disease treatment.

OBJECTIVE: We aimed to investigate the role of DIO2 polymorphisms rs225014 and rs12885300 in Graves' disease patients, mainly for controlling body weight following treatment. METHODS: We genotyped 280 GD patients by the time of diagnosis and 297 healthy control individuals using a TaqMan SNP Genotyping technique. We followed up 141 patients for 18.94 ± 6.59 months after treatment. RESULTS: There was no relationship between the investigated polymorphisms with susceptibility to GD and gain or loss of weight after GD treatment. However, the polymorphic inheritance (CC+CT genotype) of DIO2 rs225014 was associated with a lower body weight variation after GD treatment (4.26 ± 6.25 kg) when compared to wild type TT genotype (6.34 ± 7.26 kg; p = 0.0456 adjusted for the follow-up time). This data was confirmed by a multivariate analysis (p = 0.0138) along with a longer follow-up period (p = 0.0228), older age (p = 0.0306), treatment with radioiodine (p-value = 0.0080) and polymorphic inheritance of DIO2 rs12885300 (p = 0.0306). CONCLUSION: We suggest that DIO2 rs225014 genotyping may have an auxiliary role in predicting the post-treatment weight behavior of GD patients.

The change in the clinical presentation of Graves disease: a 30 years retrospective survey in an academic Brazilian tertiary center

ABSTRACT Objective Graves' disease (GD) is the main cause of hyperthyroidism among adults. It is an autoimmune condition classically marked by the Merserburg Triad (goiter, thyrotoxicosis, and orbitopathy), but the change in presentation of GD over time has rarely been studied. To determine changes in the clinical presentation of patients with GD in the last 30 years. Subjects and methods The study evaluated 475 patients diagnosed with GD between 1986 and 2016 in a single center. Patients were evaluated regarding epidemiological aspects, thyroid function, inflammatory activity of the eyes evaluated by the Clinical Activity Score; CAS, severity evaluated by NOSPECS classification and thyroid volume estimated by ultrasonography. Results Patients assessment identified an increase in the mean age of diagnosis of GD (p < 0.02), a reduction in thyroid volume (p < 0.001) and less intense orbital involvement from 2007-2016 compared to 1986-2006 (p = 0.04). The number of smoking patients was smaller from 2007 to 2016 (28.7%) than 1986 to 2006 (42.8% p = 0.001). The TSH and TRAb values did not had significant changes. Conclusion GD presentation appears to be changed in the last years compared to the typical initial presentation. There is a less frequent inflammatory involvement of orbital tissue, smaller goiters, a lower number of smokers and diagnosis at older age.

Association of serum thyrotropin levels with coronary artery disease documented by quantitative coronary angiography: a transversal study.

OBJECTIVE: The association between coronary artery disease (CAD) and thyroid function remains controversial. We evaluated the thyroid function and graduated well-defined CAD as confirmed by quantitative coronary angiography (CA). SUBJECTS AND METHODS: We evaluated the serum TSH, free thyroxine, free triiodothyronine and thyroid antibody levels in 300 consecutive patients (age 61.6 ± 9.9 years and 54% were male) undergoing CAD diagnosis as confirmed by CA. Plaques with ≥ 50% stenosis being indicative of obstructive CAD, and patients were divided into groups according to main epicardial coronary arteries with plaques (0, 1, 2, 3). Lipid profiles and a homeostasis model assessment (HOMA-IR) were determined. RESULTS: Serum median (25% and 75% percentile) TSH levels in patients with group 2 and 3 (2.25; 1.66-3.12 mU/L and 4.99; 4.38-23.60 mU/L, respectively) had significantly higher TSH concentrations (p < 0.0001) than the group 0 (1.82; 1.35-2.51 mU/L). Furthermore, patients of group 3 had higher TSH concentration (p < 0.0001) than those of group 1 (1.60; 0.89-2.68 mU/L). Group 3 were older (64 ± 8.5 vs. 59 ± 9.5, p = 0.001), had more patients with dyslipidemia (84% versus 58%, p < 0.001), male (54% versus 44%, p = 0.01), hypertension (100% versus 86%, p < 0.001), and smoking (61% versus 33%, p < 0.001) than group 0. Multivariate stepwise logistic analysis showed TSH, age, HbA1c, and HOMA-IR were the CAD associated variables. CONCLUSIONS: In this cohort, elevated TSH levels in the high normal range or above are associated with the presence and severity of CAD besides may represent a weak CAD risk factor.

Association of serum thyrotropin levels with coronary artery disease documented by quantitative coronary angiography: a transversal study

ABSTRACT Objective: The association between coronary artery disease (CAD) and thyroid function remains controversial. We evaluated the thyroid function and graduated well-defined CAD as confirmed by quantitative coronary angiography (CA). Subjects and methods: We evaluated the serum TSH, free thyroxine, free triiodothyronine and thyroid antibody levels in 300 consecutive patients (age 61.6 ± 9.9 years and 54% were male) undergoing CAD diagnosis as confirmed by CA. Plaques with ≥ 50% stenosis being indicative of obstructive CAD, and patients were divided into groups according to main epicardial coronary arteries with plaques (0, 1, 2, 3). Lipid profiles and a homeostasis model assessment (HOMA-IR) were determined. Results: Serum median (25% and 75% percentile) TSH levels in patients with group 2 and 3 (2.25; 1.66-3.12 mU/L and 4.99; 4.38-23.60 mU/L, respectively) had significantly higher TSH concentrations (p < 0.0001) than the group 0 (1.82; 1.35-2.51 mU/L). Furthermore, patients of group 3 had higher TSH concentration (p < 0.0001) than those of group 1 (1.60; 0.89-2.68 mU/L). Group 3 were older (64 ± 8.5 vs. 59 ± 9.5, p = 0.001), had more patients with dyslipidemia (84% versus 58%, p < 0.001), male (54% versus 44%, p = 0.01), hypertension (100% versus 86%, p < 0.001), and smoking (61% versus 33%, p < 0.001) than group 0. Multivariate stepwise logistic analysis showed TSH, age, HbA1c, and HOMA-IR were the CAD associated variables. Conclusions: In this cohort, elevated TSH levels in the high normal range or above are associated with the presence and severity of CAD besides may represent a weak CAD risk factor.

Outcomes in Relapsed Graves' Disease Patients Following Radioiodine or Prolonged Low Dose of Methimazole Treatment.

BACKGROUND: Low doses of antithyroid drugs (ATD) for extended periods may be an alternative for Graves' disease (GD) patients who relapse after a course of ATD. METHODS: Patients with GD relapse (n = 238) after discontinuation of ATD therapy for 12-24 months were retrospectively analyzed in a nonrandomized study. Radioiodine (RAI) treatment and L-thyroxine replacement was used in 114 patients, and a low dose of methimazole (MMI; 2.5-7 mg/daily) was used in 124 patients. Thyroid dysfunction, Graves' ophthalmopathy (GO) evolution, quality of life (QoL), and body weight were evaluated during the follow-up. RESULTS: The mean follow-up was 80.8 ± 35.3 months for the RAI group, and 71.3 ± 40.3 months for the low-dose MMI group. No notable side effects were observed in either group. Thyroid dysfunction was predominant in the RAI group (p < 0.001), and euthyroidism was more common in the MMI group (p < 0.001). GO deterioration was mainly evaluated by clinical activity score (CAS)--it was higher in the RAI group (p < 0.0005) over all periods of follow-up. Multivariate logistic analysis showed that RAI treatment was associated with no improvement in CAS during follow-up (24 months: OR = 3.51 [CI 1.02-12.03], p < 0.05; 36 months: OR = 8.46 [CI 1.47-48.58], p < 0.05; 48 months: OR = 19.52 [CI 1.70-223.10], p < 0.05; 60 months: OR = 21.1 [CI 1.5-298], p < 0.05). Kaplan-Meier survival analysis confirmed this finding (p < 0.0003). Assessment of QoL using the Short Form Health Survey's 36 parameters in stable euthyroid patients (at least six months) was similar in both groups. The RAI group patients gained more weight (p < 0.005), particularly after 24 months of follow-up. CONCLUSIONS: The use of low doses of MMI is efficient and safe, and offers better outcomes for GO than RAI treatment. Prolonged low doses of MMI may be an alternative choice for relapsed GD patients, particularly for GO patients or for patients who refuse a definitive treatment.

A randomized controlled trial to evaluate the effectiveness of 2 regimens of fixed iodine (¹³¹I) doses for Graves disease treatment.

AIM: To investigate the effectiveness of 2 fixed iodine (¹³¹I) doses for the treatment for Graves hyperthyroidism and their impact on eye disease. METHODS: We prospectively examined 76 patients who received a fixed dose of 370 MBq (group 1) and 52 patients who received 555 MBq ¹³¹I (group 2). Patients were followed up for 12 months and considered in remission when they were in a stable euthyroid or hypothyroid state in the absence of antithyroid drugs 12 months after ¹³¹I administration. Eight patients with active eye disease received a daily dose of 0.5 mg/kg prednisone per kilogram of body weight at the time of radioiodine therapy for 1 month. RESULTS: The remission rate obtained was similar in groups 1 (73.7%) and 2 (80.8%; P = 0.35). Hypothyroidism was diagnosed in 56.5% of the 370-MBq group and 71.1% of the 555-MBq group patients (P = 0.13). There was no correlation among clinical features, thyroid uptake, antibody levels, serum hormones levels, and outcome. However, logistic regression analysis demonstrated that patients with large thyroid glands had 2.4 times less chance to go into remission (odds ratio; 95% confidence interval = 1.18-4.96). None of the patients developed eye disease during any fixed-dose treatment regimen or worsened their previously diagnosed ophthalmopathy. CONCLUSIONS: Fixed doses of 370 MBq and 555 MBq ¹³¹I provided similar remission rates; however, outcome was influenced by the thyroid size. We propose that 370 MBq ¹³¹I should be the routine treatment dose for all Graves disease patients, reserving a dose of 555 MBq ¹³¹I to palpable large goiters, without any additional concern to eye disease.

Ultrasonography compared to magnetic resonance imaging in thyroid-associated Graves' ophthalmopathy.

OBJECTIVE: To compare ultrasonography (US) to magnetic resonance imaging (MRI) and the clinical activity score (CAS) in Graves' ophthalmopathy. SUBJECTS AND METHODS: Nineteen patients underwent extraocular muscle thickness measurements by US and MRI, reflectivity by US and signal-intensity ratio by MRI. There were also twelve US control subjects. RESULTS: US median thicknesses were greater than in controls. Correlation was found between US and MRI in the median thickness of the left eye rectus medial muscle as well as between signal-intensity ratio (SIR) and thickness by US. An inverse correlation was found between reflectivity and SIR in the inferior and lateral rectus. On associating the tests for detecting activity the best results were obtained with CAS plus MRI (sensitivity 75%), and US and MRI (positive predictive value 77% and specificity 80%). CONCLUSION: CAS and US results showed poor correlation with MRI results suggesting that they cannot replace each other but when combined these methods can improve the evaluation of thyroid-associated ophthalmopathy.

Ultrasonography compared to magnetic resonance imaging in thyroid-associated Graves' ophthalmopathy / Comparação de ultrassonografia à ressonância magnética nuclear na oftalmopatia de Graves associada à tiroide

OBJECTIVE: To compare ultrasonography (US) to magnetic resonance imaging (MRI) and the clinical activity score (CAS) in Graves' ophthalmopathy. SUBJECTS AND METHODS: Nineteen patients underwent extraocular muscle thickness measurements by US and MRI, reflectivity by US and signal-intensity ratio by MRI. There were also twelve US control subjects. RESULTS: US median thicknesses were greater than in controls. Correlation was found between US and MRI in the median thickness of the left eye rectus medial muscle as well as between signal-intensity ratio (SIR) and thickness by US. An inverse correlation was found between reflectivity and SIR in the inferior and lateral rectus. On associating the tests for detecting activity the best results were obtained with CAS plus MRI (sensitivity 75 percent), and US and MRI (positive predictive value 77 percent and specificity 80 percent). CONCLUSION: CAS and US results showed poor correlation with MRI results suggesting that they cannot replace each other but when combined these methods can improve the evaluation of thyroid-associated ophthalmopathy.

OBJETIVO: Comparar a ultrassonografia (US) à ressonância magnética nuclear (RMN) e o índice de atividade clínica (IAC) na oftalmopatia de Graves. SUJEITOS E MÉTODOS: Dezenove pacientes submetidos à medida da espessura dos músculos extraoculares por US e RMN, refletividade ao US e razão da intensidade de sinal (RIS) à RMN. Grupo controle para US de 12 indivíduos. RESULTADOS: Espessura mediana ao US foi maior que dos controles. Houve correlação entre US e RMN na espessura mediana dos músculos retos mediais dos olhos esquerdos e entre a RIS e a espessura ao US e correlação inversa entre refletividade e SIR nos retos inferior e lateral. Detectando atividade, os melhores resultados foram associando IAC e RMN (sensitividade de 75 por cento) e US e RMN (valor preditivo positivo de 77 por cento e especificidade de 80 por cento). CONCLUSÃO: Resultados do IAC e US mostraram pouca correlação com a RMN, sugerindo que não podem ser substituídos, mas, quando combinados, esses métodos podem melhorar a avaliação da oftalmopatia associada à tiroide.

Changes of serum cytokines in hyperthyroid Graves' disease patients at diagnosis and during methimazole treatment.

OBJECTIVE: Cytokines are involved in the pathogenesis of Graves' disease (GD), but ambiguous serum cytokine results have been described. METHODS: We studied the changes in serum interleukin (IL)-1ß, soluble IL-2 receptor (sIL-2R), IL-5, IL-6 and tumor necrosis factor (TNF)-α concentrations in 29 untreated GD patients before and after restoration of euthyroidism with methimazole (MMI) treatment compared to 25 control subjects. Eleven out of 29 GD patients had active Graves' ophthalmopathy (GO). RESULTS: Compared to controls, untreated GD patients had significantly higher median levels of serum IL-1ß (18.7 vs. 34.0 pg/ml), sIL-2R (292.5 vs. 1,585.0 pg/ml), IL-5 (1.0 vs. 9.0 pg/ml), IL-6 (3.0 vs. 5.0 pg/ml) and TNF-α (8.1 vs. 16.0 pg/ml). In euthyroidism following MMI treatment, concentrations of IL-1ß (25.0 pg/ml), sIL-2R (362.0 pg/ml), IL-5 (3.0 pg/ml), IL-6 (3.0 pg/ml) and TNF-α (5.0 pg/ml) declined significantly and were similar to controls. The greatest reductions were noted in sIL-2R (76.9%), TNF-α (68.8%) and IL-5 (66.6%) levels. Serum sIL-2R, IL-5 and TNF-α levels in active GO patients were significantly elevated, but no significant differences were observed in GD patients without GO. Using a multiple linear regression analysis, serum IL-1ß was significantly associated with free thyroxine, sIL-2R with triiodothyronine and serum thyrotropin receptor antibody (TRAb) and TNF-α with TRAb. CONCLUSION: These results support the notion that serum cytokines could be used as a marker of GD activity, and the decrease in cytokine levels might be related to the achievement of euthyroidism and the immunomodulatory effects of MMI treatment.

Genetic polymorphisms associated with cigarette smoking and the risk of Graves' disease.

OBJECTIVE: Cigarette smoking is a well-recognized risk factor of Graves' disease and, particularly, Graves' ophthalmopathy. Hence, germline polymorphisms of detoxification genes and genes belonging to the major DNA repair-apoptosis pathways might have an important role in disease susceptibility. In addition, as some of these genes are regulated by thyroid hormones, they may affect the patients' outcomes. We aimed to assess the influence of the GST, CYP and TP53 gene polymorphisms in the risk of Graves' disease and its outcome. DESIGN: Prospective case-control study. PATIENTS: A PCR-based strategy was used for GSTT1, GSTM1, GSTP1, CYP1A1 and TP53 codon 72 genotypes in a group of 400 Graves' disease patients, and to compare them to 574 control individuals with similar environmental exposure features. RESULTS: GSTM1 and GSTT1 genotypes were equally distributed in cases and controls, respectively. However, GSTP1 (P < 0.0001), CYP1A1 (P < 0.0033) and Pro/ProTP53 (P < 0.0035) variants appeared more frequently in Graves' disease patients than in controls. A multivariate analysis indicated that cigarette smoking and inheritance of GSTP1, CYP1A1 and Pro/ProTP53 variants were important risk factors for Graves' disease, but only smoking appeared as an independent risk factor for Graves' ophthalmopathy. There was no association between clinical features, including ophthalmopathy or treatment outcome, and the studied genotypes. CONCLUSION: We concluded that GSTP1, CYP1A1 and TP53, but not GSTT1 and GSTM1 germline polymorphisms, may be associated with smoking-related Graves' disease susceptibility and configure a risk profile for the disease. However, these polymorphisms do not influence the patients' response to treatment.

Subclinical hypothyroidism increases the risk for depression in the elderly.

In order to determine if subclinical hypothyroidism is a risk factor for depression in the elderly, a total of 323 individuals over 60 years old were interviewed using the Structured Clinical Interview for Diagnosis and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) for mood disturbances. Patients were divided into Group I: 252 patients (184 females, 68 males; median age: 67 years, range: 60-89 years) with elevated serum thyrotropin (TSH) levels and Group II: 71 patients (45 females, 26 males; median age: 67 years, range: 60-92 years) with diagnosis of depression. Serum TSH and free thyroxine (fT4) were measured by sensitive assays. Thyroid antibodies were determined by IRMA. Depression was observed in 24 (9.5%) Group I patients and was frequent in subclinical hypothyroidism patients (14/24 = 58.3%). On the other hand, elevated TSH levels were found in 22 (30.9%) Group II patients. Depression was observed more frequently among individuals with subclinical (74/149 = 49.7%) hypothyroidism than among individuals with overt hypothyroidism (21/125 = 16.8%) (p < 0.001). Indeed, subclinical hypothyroidism increased the risk for a patient to present depression more than four times (OR = 4.886; 95% confidence interval = 2.768-8.627). Our results demonstrate that subclinical hypothyroidism increases the risk for depression and emphasize the importance of thyroid screening tests in the elderly.

Spontaneous hypothyroidism in the follow up of Graves hyperthyroid patients treated with antithyroid drugs.

AIM: Spontaneous hypothyroidism may follow the natural course of Graves disease (GD) after treatment with antithyroid drugs (ATD). METHODS: We studied retrospectively 139 remitted Graves hyperthyroid patients treated with ATD, with a follow-up period of 17.5 years (range 6 to 25 years). Elevated serum concentration of thyroid-stimulating hormone and low serum thyroxine concentrations confirmed the diagnosis. RESULTS: Thirteen patients (median age, 41 years; 26 to 48 years) developed spontaneous hypothyroidism, 4 to 144 months (median, 48 months ) following withdrawal of ATD. The prevalence of hypothyroidism was 9.3% and the incidence was 2.3% per year (13/ 563.6 patients/year of observation). There was no association with types of drugs used or the regimens. Spontaneous hypothyroid patients showed elevated titers (P = 0.02) of serum antithyroid peroxidase antibody (TPOAb) at the end of treatment with ATD, compared with the titers found at the beginning. These patients also had higher titers of TPOAb (P = 0.01) in relation to euthyroid patients. In contrast, the changes in serum antithyroglobulin antibody titers were not significant. CONCLUSIONS: Because of the shift from euthyroidism to spontaneous hypothyroidism, GD patients demanded a strict follow up after ATD therapy. It seems that there is an effect of TPOAb on thyroid destruction.

Propylthiouracil reduces the effectiveness of radioiodine treatment in hyperthyroid patients with Graves' disease.

In order to assess the effect of propylthiouracil (PTU) or methimazole (MMI) pretreatment on patient outcome after radioiodine therapy, we examined 100 patients with Graves' disease 3, 6, 9, and 12 months after administration of a 10-mCi standard single dose of 131I. They were assigned to one of three groups: no drug (ND) treatment (30 cases); MMI (45 cases); and PTU (25 cases). Antithyroid drugs (ATD) were withdrawn 15 days before radioiodine administration. The groups were similar concerning age, gender, ATD pretreatment duration, goiter size, and initial serum triiodothyronine (T3), thyroxine (T4), free thyroxine (FT4), antithyroid autoantibody levels, 24-hour radioiodine uptake and 131I dose administered per gram of thyroid tissue. ND and MMI groups presented a similar rate of cure of 73.3% and 77.8% respectively (p = NS). In contrast, the PTU group showed a rate of cure of only 32% (p < 0.05). Logistic regression analysis indicated that PTU administration (p = 0.003) and thyroid size (p = 0.02) were the variables related to radioiodine therapy failure. Our data demonstrate that the chance of 131I treatment failure is higher in individuals using PTU than in patients using MMI or not using any ATD before radioiodine (odds ratio [OR] 5.84; 95% confidence interval [CI] 1.82-18.76) suggesting that PTU should be avoided in the treatment of patients with Graves' disease.

Thyroid autoantibodies in autoimmune diseases.

Abnormalities in the thyroid function and thyroid autoantibodies have been frequently described in patients with autoimmune diseases but seldom in antiphospholipid syndrome patients. In order to determine the prevalence of thyroid function and autoimmune abnormalities, we compared serum thyrotropin (TSH, serum free thyroxine (T4) levels, thyroid antithyroglobulin (TgAb) and antithyroperoxidase (TPOAb) levels of 25 patients with systemic sclerosis, 25 patients with rheumatoid arthritis and 13 patients with antiphospholipid syndrome to a control group of 113 healthy individuals. Evaluation included a thorough clinical examination with particular attention to thyroid disease and a serologic immune profile including rheumatoid factor, antinuclear and anticardiolipin antibody measurements. Subclinical hypothyroidism (4.2

Thyroid autoantibodies in autoimmune diseases

Anticuerpos antitiroideos en enfermedades autoinmunes. Ciertas anormalidades en la función tiroidea y anticuerpos antitiroideos han sido frecuentemente descriptos en pacientes con enfermedades autoinmunes, y más raramente en pacientes con el síndrome antifosfolipídico. Para determinar la prevalencía de anormalidades en la función tiroidea y de autoinmunidad, comparamos los niveles séricos de tirotropina (TSH) tiroxina libre en suero (T4) anticuerpos antitiroglobulina (TgAb) y antitiroperoxidasa (TPOAb) en 25 pacientes con esclerosis sistémica, 25 pacientes con artritis reumatoidea y 13 pacientes con el síndrome antifosfolipídico con un grupo control de 113 individuos aparentemente sanos. La evaluación incluyó un completo examen clínico con particular atención para las enfermedades de la tiroides y una evaluación inmunológica incluyendo dosaje del factor reumatoideo, anticuerpos antinucleares y anticardiolipina. Hipotiroidismo subclínico (4.2

The effects of early antithyroid therapy for endogenous subclinical hyperthyroidism in clinical and heart abnormalities.

Subclinical hyperthyroidism has been associated with harmful cardiac effects, but its treatment remains controversial. This study was designed to assess the cardiac effects of the normalization of serum TSH concentration in patients with endogenous subclinical hyperthyroidism. Ten patients (median age, 59 yr; range, 16-72 yr) with normal serum free T(4) and free T(3) concentration and a stable suppression of serum TSH levels were evaluated by Doppler-echocardiography, by standard and 24-h electrocardiography monitoring (Holter), and by the clinical Wayne index. Ten subjects, matched for age and sex, were used as controls. Patients were reevaluated 6 months after achieving stabilized euthyroidism by using methimazole with a median initial dose of 20 mg daily (10-30 mg daily). After reaching euthyroidism, we found a significant decrease in the heart rate (P = 0.008), the total number of beats during 24 h (P = 0.004), and the number of atrial (P = 0.002) and ventricular (P = 0.003) premature beats. Echocardiographical data resulted in a reduction of the left ventricular mass index (P = 0.009), interventricular septum thickness (P = 0.008), and left ventricular posterior wall thickness (P = 0.004) at diastole. Furthermore, the early diastolic peak flow velocity deceleration rate was significantly higher (P = 0.02) in the untreated patients compared with controls. The Wayne clinical index was higher in patients than in controls (P = 0.001) and decreased after treatment (P = 0.004). Serum TSH concentration returned to normal values after 2.5 months (range, 1.0-7.0 months) on methimazole therapy (0.05 vs. 1.42 mU/liter; P = 0.002). Serum free T(4) values were normal in patients before treatment but significantly decreased after reaching the euthyroidism (16.9 vs. 11.5 pmol/liter; P = 0.002). In contrast, serum free T(3) concentration did not differ among the groups. In conclusion, our findings support that early antithyroid therapy should be considered in patients with endogenous subclinical hyperthyroidism, where it is needed to prevent potential progression to a more advanced heart disease.