Measurement of integrated concentration of GH by means of continuous withdrawal sampling is a method of evaluating physiological hormonal secretion. Integrated concentration of GH was evaluated in 5 subjects with idiopathic hypogonadal hypogonadism (range 19\p=n-\27 years) and in a 17-year-old male with idiopathic delay of puberty (5 males, 1 female) before and 30\p=n-\240 days after the start of pulsatile GnRH administration. Gonadotropins and testosterone or 17\g=b\-estradiol were restored, whereas 24-h integrated concentration of GH (before therapy 5.4 \ m=+-\ 1.3 IU/l; during GnRH 8.1 \ m=+-\ 2.0 IU/l; P< 0.05) was increased by GnRH therapy. However, no correlation was found between GH levels and sex steroid concentrations during GnRH pulsatile administration. These data further confirm that a physiological increase in gonadotropins and sex steroids can modulate GH synthesis and/or release.