Dose-response relationships for the effects of growth hormone-releasing factor-(1-44)-NH2 in young adult men and women.

Human GRF-(1-44)-NH2 (GRF-44) was administered iv in graded doses of 0.01-10 micrograms/kg to 35 normal young adult men and 38 women. GRF-44 stimulated the release of GH in a dose-dependent fashion, although the individual responses varied widely. The ED50 values for this effect were 0.4 micrograms/kg in men and 0.2 micrograms/kg in women in the midfollicular phase of the menstrual cycle. Maximal responses in men and women were not significantly different, and a dose of 1 micrograms/kg was sufficient to produce a maximal response. There was, likewise, no difference between responses of women tested in the midfollicular and midluteal phases of the cycle. There were no changes in PRL, LH, FSH, TSH, ACTH, beta-endorphin, or cortisol at doses up to 1 microgram/kg; at 10 micrograms/kg, PRL increased by an average of 7.6 ng/ml in the women. Side effects occurred in approximately 20% of both men and women at 1 microgram/kg and in nearly all subjects given 10 micrograms/kg; these consisted primarily of flushing and a sense of warmth. Thus, a dose of 1 microgram/kg GRF-44 is safe and effective, and would appear to be a reasonable choice for use in studying GH responses in normal subjects of other ages and in patients with disorders of GH secretion.