Episodic release of prolactin in women with weight loss-related amenorrhea

Amenorrhea associated with weight loss is characterized by several neuroendocrine aberrations. The aim of the present study was to define the characteristics of episodic secretion of prolactin in women with weight loss-related amenorrhea. To evaluate whether hypoestrogenism was responsible for the changes in prolactin secretion in amenorrheic women, the pulsatile secretory pattern was also studied during hormone replacement therapy (HRT). Fifteen patients were studied by blood sampling every 10 min for 8 h. Four normally cycling women were studied as a reference group, during both the midfollicular and midluteal phases. Mean plasma prolactin levels and pulse amplitude were lower in amenorrheic patients than in controls. The prolactin pulse frequency was higher than that in controls during the follicular phase, but lower than controls during the luteal phase of the menstrual cycle. During HRT, mean plasma prolactin levels significantly increased, pulse frequency decreased and pulse amplitude significantly increased both during estradiol and estradiol plus medroxyprogesterone acetate administration. In conclusion, in amenorrhea associated with weight loss the chronobiological organization of prolactin secretion is deranged, both as a result of a neuroendocrine alteration and as a result of low plasma levels of gonadal steroids.