Oestradiol stimulates prolactin secretion in women through oestrogen receptors

To examine the effects of clomiphene and raloxifene on basal and GnRH-induced prolactin (PRL) secretion in postmenopausal women.

Postmenopausal women participated in two experimental procedures a month apart. In one experiment they received raloxifene (180 mg/day) (R-Exp) and in the other clomiphene (150 mg/day) (Cl-Exp). In Group 1, the women (n = 8) received raloxifene or clomiphene for 30 days plus oestradiol via skin patches (100 microg/24 h) for the last 10 days. In Group 2, the women (n = 8) received oestradiol for 30 days plus raloxifene (R-Exp) or clomiphene (Cl-Exp) for the last 10 days. The pituitary response to GnRH (100 microg i.v.) was investigated in all women on days 0, 10, 20 and 30 of each experiment.

The study included 16 healthy postmenopausal volunteer women aged 56-60 years.

Basal levels of PRL and the area under the curve (AUC) of DeltaPRL response to GnRH were calculated.

In Group 1, basal levels of PRL and the area under the curve (AUC) of PRL response to GnRH did not change significantly in both experiments. In Group 2, during both experiments basal levels of PRL and the AUC of PRL increased significantly on days 10 (P < 0.05) and 20 (P < 0.05) as compared to day 0 and then they decreased significantly on day 30 as compared to day 20 (P < 0.05).

Our study demonstrates for the first time that raloxifene and clomiphene affect the secretion of PRL in postmenopausal women in a similar manner. It is suggested that oestradiol stimulates the secretion of PRL in women by acting through oestrogen receptors.