The Effects of Early Antithyroid Therapy for Endogenous Subclinical Hyperthyroidism in Clinical and Heart Abnormalities

• Published in: The journal of clinical endocrinology and metabolism Vol. 88; no. 4; pp. 1672 - 1677
• Main Authors: Sgarbi, José A., Villaça, Fábio G., Garbeline, Benito, Villar, HeloÍsa E., Romaldini, João H.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Oxford University Press 01.04.2003; Copyright by The Endocrine Society; Endocrine Society
• Subjects: Adolescent; Adult; Aged; Antithyroid Agents - therapeutic use; Arrhythmias, Cardiac - etiology; Arrhythmias, Cardiac - prevention & control; Arrhythmias, Cardiac - therapy; Biological and medical sciences; Diastole; Doppler effect; Echocardiography; EKG; Electrocardiography; Endocrinopathies; Female; Flow velocity; Heart diseases; Heart Diseases - etiology; Heart Diseases - pathology; Heart Diseases - prevention & control; Heart Rate; Heart Ventricles - pathology; Hormones. Endocrine system; Humans; Hyperthyroidism; Hyperthyroidism - complications; Hyperthyroidism - drug therapy; Hyperthyroidism - physiopathology; Male; Medical sciences; Methimazole - administration & dosage; Methimazole - therapeutic use; Middle Aged; Non tumoral diseases. Target tissue resistance. Benign neoplasms; Patients; Pharmacology. Drug treatments; Systole; Thyroid Gland - physiopathology; Thyroid. Thyroid axis (diseases); Thyrotropin - blood; Thyroxine - blood; Triiodothyronine - blood; Tropical medicine; Ventricle; South America; Brazil; America; Endocrinopathy; Cardiovascular disease; Thyroid stimulating hormone; Asymptomatic; Myocardial disease; Blood plasma; Electrodiagnosis; Heart disease; Electrocardiography; Adult; Complication; Hormonal investigation; Sonography; Human; Antithyroid agent; Echocardiography; Treatment efficiency; Hyperthyroidism; Thyroid diseases; Chemotherapy; Treatment; Adenohypophyseal hormone; Adolescent; Early; Elderly
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/jc.2002-021046

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 T4 and free T3 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 T4 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 T3 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.