Effect of Triiodothyronine Treatment on Prolactin Secretion in Patients with Amenorrhea-Galactorrhea

Abstract

In order to determine the role of thyroid hormone in prolactin (PRL) secretion in patients with amenorrhea-galactorrhae, PRL response to 500 mug of iv thyrotropin-releasing hormone (TRH) was studied before and after the administration of triiodothyronine (T3) in 10 patients with amenorrhea-galactorrhea. Seven of these patients were euthyroid and the other 3 had hypothyroidism. The patients in the euthyroid group received 50 mug of T3 daily for 7 days and 75 mug q.d. for the ensuing 14 days. The hypothyroid patients received T3 at progressively increasing doses from 10 mug q.d. to 75 mug q.d. during 34 to 68 days. In the initial test, the elevated basal levels of PRL, 61.9 +/- 9.8 ng/ml (Mean +/- SE) exhibited a slight but insignificant net increase (7.7 +/- 2.1 ng/ml) after TRH injection in the euthyroid group. However, a marked response to TRH with a net increase of 147.2 +/- 26.3 ng/ml from the basal level of 47.3 +/- 11.2 ng/ml was observed in the hypothyroid patients. After treatment with T3, both the basal level (56.9 +/- 8.3 ng/ml) and the net increase (9.9 +/- 3.6 ng/ml) of PRL following TRH stimulation remained virtually unchanged in the euthyroid group. The hypothyroid group, in contrast, displayed a significant depression of both the basal level (26.1 +/- 13.0 ng/ml) and the net increase (33.8 +/- 6.5 ng/ml) of PRL to TRH stimulation. The diminution of the basal levels and responses of thyroid-stimulating hormone (TSH) to TRH stimulation was observed in all cases of both groups. These results suggest that the level of thyroid hormone has little pathogenic role in PRL secretion in euthyroid patients with amenorrhea-galactorrhea, in contrast to its marked effect in hypothyroid patients with amenorrhea-galactorrhea.