Effect of dexamethasone on prolactin secretion in late pregnancy.

It is established that PRL secretion is regulated by estrogens. Glucocorticoids, on the other hand, suppress estrogen secretion during pregnancy and may also inhibit PRL by direct hypothalamopituitary action. In this study PRL and estradiol were determined with specific radioimmunoassays in 14 women during gestational weeks 28 to 34 prior to, during, and following short-term intramuscular dexamethasone administration (12, 8, and 4 mg on three consecutive days) used for prophylaxis of RDS in preterm infants. There were no significant alterations in PRL serum concentrations; estradiol showed a significant drop (P less than 0.001) during all 3 days of treatment, returning to the pretreatment level on posttreatment day 1. The PRL and TSH responses to 200 micrograms of intravenous TRH on day 2 or 3 of dexamethasone treatment in six women during late pregnancy were not inhibited. Short-term dexamethasone treatment with pharmacologic doses does not suppress the physiologic secretion and release of PRL or the release induced by TRH during late pregnancy.