Pulsatility of serum LH in pathological conditions

Abstract

LH pulsatility changes throughout the normal menstrual cycle. The number of LH pulses increases during the first days after menstruation, remains unchanged thereafter until after ovulation and declines progressively during the luteal phase. LH pulse amplitude is highest during midcycle. In hypothalamic amenorrhea, gonadotropin levels are reduced. This appears to be a consequence of a reduction of hypothalamic Gn-RH secretion which is reflected by a diminished frequency and amplitude of LH pulses during the 24-hour span. Administration of an opiate antagonist, naloxone, increases LH pulse frequency in those patients, and in patients with secondary hypothalamic amenorrhea the daily oral administration of naltrexone, another specific opiate antagonist, induces ovulatory cycles. Patients suffering from hyperandrogenemia may present with eumenorrhea, oligomenorrhea or amenorrhea. There is an increase in mean LH levels and of the LH/FSH ratio with increasing severity of the ovarian disturbance. The increase in mean LH levels is a consequence of an increase in LH pulse amplitude while LH pulse frequency is not changed compared to the early follicular phase of the menstrual cycle.