Endocrine effects of GnRH analogue with low-dose hormone replacement therapy in women with endometriosis.

Objective: GnRH analogues are being used increasingly for a number of oestrogen dependent conditions in women. The resultant profound hypo-oestrogenism is a disadvantage, however, but the preservation of pituitary sensitivity to negative feedback by oestradiol is not well defined. We have determined the effect on gonadotrophins and inhibin of GnRH analogue plus low-dose continuous combined hormone replacement therapy in comparison with GnRH analogue therapy alone.
Design: Randomized controlled trial.
Patients: Fifty premenopausal women with endometriosis randomized to treatment with goserelin alone (Group 1) or goserelin plus 17 beta-oestradiol and medroxyprogesterone acetate (Group 2).
Measurements: FSH, LH, oestradiol, oestrone, inhibin before and during treatment.
Results: Oestradiol and oestrone were suppressed in both groups, but Group 2 had significantly higher oestradiol during the hormone replacement therapy period. LH was suppressed in both groups. In Group 1, FSH levels recovered during treatment but, in contrast, in Group 2, FSH levels remained suppressed throughout treatment. Inhibin was significantly lower in Group 2, but not in Group 1, during treatment compared to pretreatment.
Conclusions: Pituitary secretion of FSH appears to remain responsive to feedback control by oestradiol during GnRH analogue therapy and is incompletely suppressed, unlike LH which remains completely suppressed. The possible mechanisms for this are discussed.