Male reproductive endocrinology

Abstract

Knowledge of the endocrine mechanisms controlling male reproductive function has increased enormously in the last fifteen years. Accurate measurement of plasma levels of gonadotropins and sex steroids, identification of the hypothalamic gonadotrophin releasing hormone (GnRH) and, more recently, characterization of the interaction of these hormones with specific receptors in target organs, are a few examples of the progress which has been made. But despite these important advances, the major clinical problem in male reproduction - that of the infertile man - seems no nearer resolution. This contrasts strongly with female reproduction in which application of recent knowledge of hormonal control of the menstrual cycle has enabled us to treat successfully the majority of infertile patients with ovulatory failure. The reason for the disparity is clear; endocrine disorders manifesting as anovulation account for 20 per cent or more of women with infertility, whereas clear-cut endocrine abnormalities are uncommon in subfertile men. Nevertheless, hormone measurements do have a part to play in the management of the infertile man. It is the aim of this chapter to review briefly the physiology of male reproductive endocrinology, to describe abnormalities of testicular function and to discuss the place of endocrine investigations in the management of hypogonadism and male infertility.