Galactorrhea in Subclinical Hypothyroidism

Abstract

Galactorrhea was found in 5 patients with subclinical hypothyroidism. The galactorrhea consisted of the discharge of a few drops of milk only under pressure. Serum T4was in the lower level of the normal range, but serum T3was normal (T4: 6.3±1.2 μg/dl, T3: 113±7ng/dl). Basal serum TSH and PRL were slightly increased only in 2 and 1 cases, respectively. The PRL responses to TRH stimulation were exaggerated in all cases, although the basal levels were normal. An enlarged pituitary gland was observed in 1 patient by means of CT scanning. All patients were treated by T4replacement. In serial TRH tests during the T4replacement therapy, the PRL response was still increased even when the TSH response was normalized. Galactorrhea disappeared when the patients were treated with an increased dose of T4(150-200μg/day). Recurrence of galactorrhea was not observed even though replacement dose of T4was later decreased to 100 μg/day in 4 cases. In patients with galactorrhea of unknown origin, subclinical hypothyroidism should not be ruled out even when their serum T4, T3, TSH and PRL are in the normal range. The TRH stimulation test is necessary to detect an exaggerated PRL response, as the cause of the galactorrhea. To differentiate this from pituitary microadenoma, observation of the effects of T4replacement therapy on galactorrhea is essential. © 1987, The Japan Endocrine Society. All rights reserved.