Clinical and therapeutic controversies on subclinical hyperthyroidism

Subclinical hyperthyroidism is defined as low or undetectable serum thyrotropin concentration in the presence of levels of free thriiodothyronine and thyroxine within the reference range. Despite the conflicting results from many observational studies, this thyroid disorder has been associated with an increased risk of developing atrial fibrillation, left ventricular hypertrophy, increased heart rate and diastolic function impairment. In addition, a relation between subclinical hyperthyroidism, skeletal disorders and cognitive changes has been reported. Treatment of subclinical hyperthyroidism remains controversial, given the lack of prospective randomized studies showing clinical benefits with restoration of the euthyroid state. Nevertheless, this review recommends the treatment of subclinical hyperthyroidism to individuals aged over 65, postmenopausal women, patients with cardiac risk factors, heart disease, osteoporosis or hyperthyroidism symptoms, whenever TSH is persistently suppressed (,0.1mU/L). When TSH is between 0.1 – 0.5mU/L, treatment should be considered for individuals over age 65, patients with heart disease or hyperthyroidism symptoms.