LH PULSATILITY AND INVITRO BIOACTIVITY IN WOMEN WITH ANOREXIA NERVOSA-RELATED HYPOTHALAMIC AMENORRHEA

LH nocturnal pulsatility and bioactivity to immunoreactivity (B/I) rat io were determined in 16 patients with anorexia nervosa-related hypoth alamic amenorrhea and low sex steroid levels, and in 12 normal women i n the midfollicular phase. The patients were subdivided into 2 groups: IA (N = 7) without, and IB (N = 9) with documented recent weight gain . Blood samples were taken from each subject at 10-min intervals from 00.00 to 06.00 h. Immunoreactive LH data were analysed with cluster an alysis algorithm. A pool of aliquots from all the samples was used to evaluate bioactive LH, immunoreactive LH and LH B/I ratio in each subj ect. LH pulse frequency was lower in Group IA than in controls, wherea s it did not differ significantly between Group IB and controls. LH pu lse amplitude was lower in Group IA, and higher in Group IB than in co ntrols. LH B/I ratio was below the control range in 3/16 patients. In conclusion, persistent hypothalamic amenorrhea does not require a perm anent inhibition of the GnRH pulse generator; transient inhibition of pulsatility and qualitative abnormalities of gonadotropins could be in volved in the mechanism, at least in some patients.