[Subclinical hyperthyroidism: not necessarily a thyroid disorder].

Three women, aged 16, 70 and 72 years, were seen in our outpatients' clinics with a decreased TSH value. In two of them, thyroid dysfunction was not the cause of the low TSH activity. In patient A, the cause was diminished food intake and in patient B, who was also known with nodular thyroid disease, the cause was the use of glucocorticoids. Only patient C had subclinical hyperthyroidism due to goitre with concomitant atrial fibrillation. She was recommended for treatment with 131I. Patients A and B recovered spontaneously. Subclinical hyperthyroidism is being increasingly encountered due to the availability of sensitive assays for measuring TSH activity and the increased frequency with which general practitioners test thyroid function. However, in about 55% of cases suppressed TSH values normalise spontaneously. This means that it is important to establish if thyroid disease is truly present. The treatment of subclinical hyperthyroidism should be initiated on the basis of individual data.