Alteration of the hypothalamus-pituitary-testis axis in oligozoospermic men with normal gonadotropin levels.

BACKGROUND: Serum basal hormone levels such as lutenizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone, which is important to regulate testicular function, do not necessarily indicate the normal integrity of the hypothalamic-pituitary-testicular axis and the static measurement is not enough to detect the endocrine disorder. The dynamic measurement of gonadal hormone by GnRH test is considered to be more helpful to understanding the endocrine regulation of spermatogenesis. In this study, we performed GnRH test in oligozoospermic patients with normal levels of LH and FSH to examine the subtle alteration of hypothalamic-pituitary-testis axis.

METHODS: GnRH test was performed in 41 patients with oligozoospermia and normal gonadal hormone levels.

RESULTS: The responses of LH and/or FSH were excessive in most patients in spite of their normal gonadotropin levels. The patients with sperm concentration < 10 x 10(6)/ml had significantly higher peak levels of both LH and FSH than did those with sperm concentration > 10 x 10(6)/ml. In the patients with normal peak levels of both LH and FSH, sperm concentration was significantly higher than those with exceeded peak levels of FSH and/or LH after GnRH test. No significant differences were observed in estradiol, testosterone, free testosterone, or prolactin (PRL) levels between patients with normal responses and abnormal responses of LH and/or FSH.

CONCLUSIONS: The feedback control of gonadotropin release from testis was worse in more severely oligozoospermic patients, although the precise mechanism of feed back still remains unknown.