Growth hormone (GH) substitution in hypogonadotropic, GH-deficient women decreases the follicle-stimulating hormone threshold for monofollicular growth

The FSH threshold concept for monofollicular growth (which means that at the time the largest follicle reaches 18 mm there are no other follicles with a diameter of 13-18 mm also present) was used during ovulation induction in hypogonadotropic women, who appeared to be GH deficient. This concept was used to investigate whether 1) GH influences the FSH threshold for monofollicular growth and 2) whether such an influence would depend upon the endogenous GH/insulin-like growth factor I (IGF-I)/IGF-binding protein-3 (IGFBP-3) levels. In six hypogonadotropic women the GH response after an insulin challenge did not exceed 6 mu g/L. Patients underwent ovulation induction according to a low dose step-up protocol by hMG during two consecutive cycles. GH substitution was provided only during the second cycle. Except for one GH treated cycle, all cycles were ovulatory. IGF-I levels as well as IGFBP-3 levels significantly increased (P < 0.01) during GH substitution. Monofollicular growth was not achieved in the first cycles. In five of six GH-substituted cycles, monofollicular growth was obtained. FSH threshold levels decreased in all patients during GH substitution. The FSH area under the curve was negatively correlated to IGF-I (r = -0.6; P < 0.05) and IGFBP-3 (r = -0.6; P < 0.05). The results of this study indicate that GH may play a role in the physiological growth of the follicle; most likely this occurs by influencing the IGF-I or IGFBP-3 levels. GH appears to selectively increase the sensitivity of the dominant follicle to FSH, facilitating monofollicular growth.