NEUROHYPOPHYSEAL HORMONE-SECRETION IN HYPERPROLACTINEMIC WOMEN

Prolactin (PRL) has been reported to promote antidiuresis and increase intestinal water-electrolyte absorption, whereas osmolar changes have been shown to influence PRL secretion. However, the mechanisms of act ion of PRL on the salt-water balance remain unclarified. The present c linical study targeted the effects of hyperprolactinaemia on the secre tion of arginine-8-vasopressin (AVP), oxytocin (OXT) and cortisol. Pla sma AVP and OXT were measured by radioimmunoassay, and cortisol by flu orimetry. In healthy women (21-39 y, n=6), an oral water load (OWL, 20 ml/bw) significantly suppressed the plasma levels of AVP, OXT and cor tisol, and the PRL level too tended to decrease. In hyperprolactinaemi c females (22-41 y, n=6, three with pituitary adenomas), water retenti on was registered following an OWL, together with paradoxical AVP and OXT level increases, whereas the cortisol response remained normal, an d the PRL level did not change at all. Histamine (0.5 mg sc) stimulate d the release of AVP, OXT and cortisol in the control and hyperprolact inaemic groups alike. These data suggest that alterations in AVP and O XT hypersecretion may contribute to the water retention in hyperprolac tinaemia.