RECIPROCAL PATTERN OF THE TSH AND PRL RESPONSES TO DOPAMINE RECEPTOR BLOCKADE IN WOMEN WITH PHYSIOLOGICAL OR PATHOLOGICAL HYPERPROLACTINAEMIA

Abstract
The TSH and PRL [prolactin] responses to administration of the 2 dopamine (DA) receptor antagonists sulpiride and domperidone, were studied in 15 normoprolactinemic subjects, 22 post-partum women and 16 subjects with presumptive evidence of (6 subjects) or surgically confirmed (10 subjects) prolactinomas. Sulpiride (100 mg i.m.) or domperidone (10 mg i.v.) elicited a slight increase in basal TSH levels in both normoprolactinemic and post-partum women, but induced a clear-cut TSH rise in subjects with a tumor. Conversely, sulpiride and domperidone strikingly stimulated PRL secretion in normoprolactinemic and post-partum women, but only slightly enhanced baseline PRL levels in women with prolactinomas. The reason for the reciprocal pattern of TSH and PRL responsiveness to DA receptor blockade of post-partum women and subjects with prolactinomas is presently obscure. Since baseline PRL levels in the 2 hyperprolactinemic states overlapped widely, it would appear that hyperprolactinemia per se is not responsible for such behavior.