QUANTITATIVE AND QUALITATIVE CHANGES IN LH SECRETION FOLLOWING PULSATILE GnRH THERAPY IN A MAN WITH IDIOPATHIC HYPOGONADOTROPHIC HYPOGONADISM

Abstract

The pattern of bioactive and immunoreactive LH secretion before and during pulsatile GnRH therapy (18 micrograms/90 min) in a hypogonadotrophic hypogonadal male has been studied. Before treatment the patient was azoospermic and had low testosterone (1.2 nmol/l) with low and apulsatile immunoreactive LH (1.9 +/- 0.2 IU/l) and FSH (1.4 +/- 1.9 IU/l) levels. There was no detectable LH bioactivity. During the first 24 h of GnRH therapy there was a small increase in immunoreactive (5.4 +/- 0.8 IU/l) and bioactive (6.7 +/- 1.3 IU/l) LH, with an irregular pattern and little effect on testosterone production (2.2 nmol/l). Within 1 week of treatment both bioactive (30.5 +/- 6.8 IU/l) and immunoreactive (13.6 +/- 1.5 IU/l) LH levels were above the normal range and the pattern of secretion was pulsatile. The bioactive to immunoreactive (B:I) LH ratios within the pulses (2.6 +/- 0.3) were higher (P less than 0.01) than between pulses (1.97 +/- 0.1) and the testosterone concentration (17.8 +/- 2.1 nmol/l) was now normal. At one month LH secretion was similar and testosterone pulses of high amplitude were evident corresponding to high-amplitude bioactive LH pulses. By 3 months mature spermatozoa (1.3 x 10(6)/ml) were seen in the patient's semen. The pattern of LH secretion was pulsatile but the levels of bioactive (13.1 +/- 3.6 IU/l) and immunoreactive (9.5 +/- 1.3 IU/l) LH decreased towards the normal range reflecting maturation of the testicular feedback control at the pituitary level. This effect was more pronounced on bioactive rather than immunoreactive LH secretion (57% vs 32% relative decrease). At 6 months LH levels were similar and the sperm count was normal (34 x 10(6)/ml).