Growth hormone treatment affects plasma LH pulsatile release in women with secondary amenorrhoea

Since growth hormone (GH) is administered as a co-gonadotrophic factor in ovulation induction, this study aimed to assess the action of GH on the episodic pulsatile release of LH and FSH in amenorrhoeic patients.

Nineteen patients affected by hypothalamic amenorrhoea were enrolled for this study: group A, 9 patients with normal gonadotrophins; group B, 10 patients with low gonadotrophins. Both groups were studied during GH infusion (0.015 IU/min for 4 hours) and after 7 days of GH administration (0.1 IU/kg/day). Patients underwent a 4-hour pulsatility study, with blood sampling every 10 minutes. A standard GnRH test (10 micrograms i.v. bolus) was performed immediately after the pulsatility evaluation.

LH and FSH were assayed with an IFMA method; oestradiol and IGF-I were assayed by RIA and IRMA, respectively. PULSE DETECTION: Time series were analysed with Detect program.

All patients showed similar LH and FSH pulsatile characteristics both under baseline conditions and during GH infusion. After 7 days of GH administration, episodic FSH release showed no change in either group. On the contrary, LH pulse frequency (mean +/- SE) significantly increased in group A (4.0 +/- 0.2 peaks/4h, P < 0.05), while pulse amplitude (baseline, 3.9 +/- 0.6 IU/l; after 7 days, 2.9 +/- 0.3 IU/l, P < 0.05), and integrated LH plasma concentrations (baseline, 7.6 +/- 1.1 IU/l; after 7 days, 5 +/- 0.8 IU/l, P < 0.05) were significantly decreased. No significant changes were observed for LH pulse frequency, amplitude or integrated LH plasma concentrations in hypogonadotrophinaemic patients (group B). Plasma oestradiol levels were significantly increased only in group A (baseline, 154.18 +/- 23.8 pmol/l; after 7 days, 380.3 +/- 110.1 pmol/l, P < 0.05), while IGF-I levels were significantly increased in both groups after 7 days of GH administration (P < 0.05). No significant differences were observed in the gonadotrophin responses to GnRH test before and after GH administration.

The present study showed that the administration of GH in amenorrhoeic patients determines the significant changes in episodic LH release in those subjects with normal LH plasma levels and suggests that the action of GH may be dependent upon the ovarian-pituitary feedback action.