| Popis: |
In this presentation we discuss how male reproductive hormones are influenced by various normal and abnormal situations. Puberty is characterized by a progressive increase in serum gonadotropins (FSH and LH) and testosterone. Hormonal profiles in aging men and rats differ significantly, suggesting qualitatively different age-related changes in both species. Gonadal disorders in humans may exhibit similar symptoms (such as delayed or precocious virilization) but may be due to different defects within the hypothalamo-pituitary-testicular axis and, hence, may exhibit different reproductive hormone profiles. Reproductive hormone measurements reveal that toxic agents, such as ketoconazole, alcohol, or opiates, can impair reproductive function at the gonad and/or the hypothalamo-pituitary level. Glucocorticoids released during stress have been shown to have a direct inhibitory effect on testosterone release from the testes, which may be of relevance to toxicology studies. Reproductive hormonal measurements have also revealed that LH levels in the blood fluctuate in a pronounced episodic fashion and that this pattern is due to the pulsatile delivery of GnRH to the anterior pituitary gland. Administration of GnRH in a pulsatile fashion to patients with hypogonadotropic hypogonadism restores gonadal function. Nonpulsatile GnRH delivery to the anterior pituitary suppresses LH and testosterone release, and, consequently, long-acting superanalogs of GnRH appear to be effective in the treatment of prostatic cancer and true precocious puberty. The examples presented in this article illustrate how hormonal measurements have increased our knowledge and understanding of male reproduction. |
