d-fenfluramine/prolactin response throughout the menstrual cycle: evidence for an oestrogen-induced alteration

The prolactin (PRL) response to fenfluramine (FEN), a serotonin (5-HT) releasing agent, is used as an index of 5-HT sensitivity in studying disorders associated with central 5-HT abnormality. Plasma oestrogen levels are known to augment PRL responses to a variety of stimuli. In order to examine the effect that ovarian steroids have on this response nine, healthy women were tested twice at three time points in the menstrual cycle: early follicular, mid-cycle and late luteal phase with either d-FEN, a more specific 5-HT agent than the racemic mixture, or placebo. Responses to d-FEN were maximal at mid-cycle, lowest during the early follicular phase, with responses premenstrually being intermediate between the two. Responses to placebo did not vary. Plasma oestradiol levels fluctuated in parallel with neuroendocrine responses to d-FEN. The possible mechanisms are discussed, including an effect that oestradiol may exert at central serotonin sites.