GONADOTROPIN REQUIREMENTS OF THE DEVELOPING FOLLICLE

Objective: To evaluate follicular FSH and LH requirements during suppr ession of endogenous gonadotropins with the GnRH antagonist Nal-Glu an d whether LH-like activity could be supplied by administering subcutan eous hCG. Design: Randomized clinical trial. Participants: Thirty-two normally cycling females in the late follicular phase (dominant follic le mean diameter greater than or equal to 14 mm). Intervention: Twelve normal women were randomized to receive 150 IU IM FSH with or without 75 IU SC hCG; 11 subjects were randomized to receive 225 IU FSH with or without 50 IU SC hCG; 9 women received 150 or 225 IU IM hMG. Subjec ts returned the next day for repeat blood sample and ultrasound. Resul ts: Continued follicular maturation, as evidenced by rising E(2) level s, correlated with serum immunoactive and bioactive FSH levels and was unrelated to bioactive LH-hCG. Two hundred twenty-five international units of exogenous FSH consistently supported follicular maturation. T here was a similar increase in mean follicular diameter in women with an E(2) rise versus those with a plateau or fall. In subjects receivin g SC mini-dose hCG, serum bioactive LH-hCG levels were increased signi ficantly and were similar to levels before Nal-Glu.Conclusions: During administration of a GnRH-a, the maturing follicle appears to require only FSH support. In markedly hypogonadotropic women, mini-dose hCG ma y be a more practical alternative to recombinant LH to promote normal follicle maturation.