Elevated FSH concentrations in imminent ovarian failure are associated with higher FSH and LH pulse amplitude and response to GnRH

Imminent ovarian failure (IOF) in women is characterized by regular menstru al cycles and elevated early follicular phase FSH, This study explored unde rlying neuroendocrine causes of elevated FSH concentrations on day 3 of the menstrual cycle. The characteristics of episodic secretion of FSH and LH, the pituitary response to gonadotrophin-releasing hormone (GnRH), plasma oe stradiol, and dimeric inhibin A and inhibin B on day 3 mere compared in 13 women with elevated FSH concentrations (>10 IU/l) and 16 controls, FSH ampl itudes were higher in the IOF group than in the controls (P < 0.0001). The FSH pulse frequency did not differ between groups. The FSH response to GnRH was higher in the IOF patients than in the controls (P < 0.0001). Mean LH, LH amplitude and LH response to GnRH were higher in the IOF group, but LH pulse frequency did not differ between the groups. Concentrations of inhibi n A and inhibin B were lower in the IOF group, while oestradiol showed no d ifferences. We concluded that in women with IOF, the pituitary is more sens itive to GnRH. This leads to higher FSH and LH pulse amplitudes which under lie the elevated FSH concentrations in the early follicular phase.