Medical hypophysectomy: II. Variability of ovarian response to gonadotropin therapy.

In an attempt to control individual variability of ovarian response to gonadotropin therapy, ovulatory monkeys received either "pure" follicle-stimulating hormone (FSH) or human menopausal gonadotropin (hMG), with or without gonadotropin-releasing hormone (GnRH) antagonist administration. Among females that responded to gonadotropin therapy, the GnRH antagonist reduced (P less than 0.05) the variability of serum estradiol patterns. Surprisingly, after pretreatment and concurrent administration of the GnRH antagonist, FSH alone was as effective as the FSH/luteinizing hormone (LH) mixture (hMG) in stimulating follicular maturation, even when serum LH levels were at or below the limits of detection. The results indicate that in a rapidly reversible hypogonadotropic state approaching a "medical hypophysectomy," concurrent gonadotropin therapy produces a less varied ovarian response. The relative (un)importance of LH in the primate ovarian cycle seems diminished in the face of evidence that FSH alone, or in the presence of vanishingly small amounts of LH, supports follicular maturation and dynamic estrogen biosynthesis.