THE DIAGNOSTIC VALUE OF PHARMACODYNAMIC TESTS IN THE HYPERPROLACTINAEMIC SYNDROME

Abstract

Patterns of prolactin (PRL) secretion were studied in a group of 18 hyperprolactinemic patients with galactorrhoea and menstrual disorders and in a control group of 32 women in the early puerperium (24 h after a normal delivery) following provocative (TRH [thyroliberin] and chlorpromazine) and suppressive (L-dopa and bromocriptine) stimuli. Out of the 18 hyperprolactinemic patients tested, 5 had radiological evidence of a pituitary tumor, and 2 were treated surgically. The early puerperium patients with elevated basal PRL levels (100-700 ng/ml) demonstrated a significant PRL response to the various treatments. In the hyperprolactinemic group, an impaired PRL response to TRH, chlorpromazine and L-dopa was noted in patients with basal PRL levels higher than 30 ng/ml, whereas bromocriptine suppressed effectively PRL levels in all the hyperprolactinemic patients tested irrespective of their basal PRL concentrations. The ratio between the fall in PRL concentrations (as percent of the baseline) after L-dopa administration (.DELTA.%L) vs. the PRL decrement after bromocriptine treatment (.DELTA.%B) was calculated. In the early puerperium group with normal pituitary prolactin secreting cells this ratio was equal to 0.8. In the hyperprolactinemic group, the 5 patients with radiological evidence of a pituitary tumor had significantly lower ratios ranging from 0.2-0.57. In terms of prolactin release, prolactin producing tumor cells are apparently intrinsically refractory to hypothalamic dopaminergic signals. The calculation of individual .DELTA.%L/.DELTA.%B ratios may serve, therefore, as a valuable indicator for early detection of autonomous pituitary prolactin secreting cells and for evaluation of the extent of the pituitary lesion.