Pituitary response to LHRH in long-term users of injectable contraceptives.

The site of gonadotrophin inhibition in long-term users of injectable contraceptives is still debatable. The pituitary response to LHRH (50 micrograms, I.V.) was assessed in 32 women. Sixteen cases were using either medroxyprogesterone acetate (DMPA; n = 8 150 mg I.M. every three months) or norethisterone enanthate (NET-EN; n = 8, 200 mg every 2 months) for at least 18 months. The remaining cases (n = 16) were normal fertile females not using any hormonal contraceptive (control group). The pituitary response to LHRH injection in both injectable subgroups was nearly identical to that in the control group. Neither the basal levels nor the net increase in gonadotrophins following LHRH injection were significantly different in the study groups from those of the control group. Long-term use of DMPA or NET-EN does not affect the pituitary responsiveness to LHRH injection and the pituitary is not a primary site for ovulation inhibition in these cases.