Journal of Clinical Endocrinology & Metabolism, Vol 55, 897-901, Copyright © 1982 by Endocrine Society

ARTICLES

Functional characterization of hypothalamic hyperprolactinemia

C Ferrari, P Rampini, R Benco, R Caldara, C Scarduelli and PG Crosignani

PRL secretory dynamics were evaluated by several stimulation and suppression tests in nine patients with hyperprolactinemia due to organic hypothalamic disease. Basal PRL levels ranged between 20-63 ng/ml. There was a normal PRL response to TRH in eight cases (i.e. doubling of basal levels), whereas none of the seven tested subjects responded to sulpiride. The same dissociation of responses was not observed in any of the patients who were still hyperprolactinemic after surgery. Concomitant dopamine infusion resulted in sulpiride-induced PRL release in the four subjects so studied. None of 50 other hyperprolactinemic patients (11 with macroprolactinoma, 18 with microprolactinoma, and 21 with idiopathic hyperprolactinemia) showed PRL response to TRH but not to sulpiride. The TRH-induced PRL increase was significantly higher than that induced by sulpiride in hypothalamic hyperprolactinemia and significantly lower in idiopathic disease as well as in healthy controls; no differences were found in prolactinoma patients. The administration of substances resulting in stimulation of pituitary dopamine receptors, such as dopamine and L-dopa, induced a normal PRL suppression in 7 patients with hypothalamic disease so tested, whereas central nervous system-acting dopaminergic drugs, such as carbidopa plus L-dopa and nomifensine, failed to lower PRL levels in most cases (even when normoprolactinemic after surgery). These data suggest that the mild to moderate hyperprolactinemia found in many patients with hypothalamic lesions is due to dopamine deficiency at the pituitary level, that TRH and dopamine receptors at the lactotropes are intact in this condition, and that paired TRH and sulpiride tests may be of some diagnostic utility in hyperprolactinemic patients. They further suggest that subjects with so-called idiopathic hyperprolactinemia do not suffer from the type of hypothalamic derangement exhibited by patients with organic lesions of the hypothalamus.