Male Infertility - Overview

Approximately 15% of couples attempting their first pregnancy meet with failure. Important issues related to the evaluation of the male factor include the most appropriate time for the male evaluation, the most efficient format for a comprehensive male exam, and definition of rationale and effective medical and surgical regimens in the treatment of these disorders. Unduly prolonged unprotected intercourse should not be advocated before a workup of the man is instituted. Initial screening of the man should be considered whenever the patient presents with the chief complaint of infertility. This initial evaluation should be rapid, non-invasive and cost effective.

MALE REPRODUCTIVE PHYSIOLOGY

The Hypothalamic-Pituitary-Gonadal Axis

The hypothalamus releases GnRH in a pulsatile nature which appears to be essential for stimulating the production and release of both luteinizing hormone (LH) and follicle stimulating hormone (FSH). Testosterone, the major secretory product of the testes, is a primary inhibitor of LH secretion in males. The mechanism of feedback control of FSH is regulated by a Sertoli cell product called inhibin. Prolactin also has a complex inter-relationship with the gonadotropins, LH and FSH. In males with hyperprolactinemia, the prolactin tends to inhibit the production of GnRH. Besides inhibiting LH secretion and testosterone production, elevated prolactin levels may have a direct effect on the central nervous system.

Testis

In the intact testis, LH receptors decrease or down-regulate after exogenous LH administration. Estrogen inhibits some enzymes in the testosterone synthetic pathway and therefore directly effects testosterone production. 44% is bound to testosterone-estradiol-binding globulin or TeBG, also called sex hormone-binding globulin. 54% of testosterone is bound to albumin and other proteins. These steroid-binding proteins modulate androgen action. The biological actions of androgens are exerted on target organs that contain specific androgen receptor proteins.

The germinal cells. The seminiferous tubules contain all the germ cells at various stages of maturation and their supporting Sertoli cells. Sertoli cells are a fixed-population of non-dividing support cells. Sertoli cells appear to be involved with the nourishment of developing germ cells as well as the phagocytosis of damaged cells.

Spermatogenesis is a complex process whereby primitive stem cells or spermatogonia, either divide to reproduce themselves for stem cell renewal or they divide to produce daughter cells that will later become spermatocytes. The spermatids then undergo a transformation into a spermatozoa. Groups of germ cells tend to develop and pass through spermatogenesis together. This sequence of developing germ cells is called a generation. There are six stages of seminiferous epithelium development. LH effects spermatogenesis indirectly in that it stimulates androgenous testosterone production. FSH targets Sertoli cells. Androgen-binding protein which is a Sertoli cell product carries testosterone intracellularly and may serve as a testosterone reservoir within the seminiferous tubules in addition to transporting testosterone from the testis into the epididymal tubule.

Transport-Maturation-Storage of Sperm Although the testis is responsible for sperm production, the epididymis is intimately involved with the maturation, storage and transport of spermatozoa. Spermatozoa gain progressive motility and fertilizing ability after passing through the epididymis. The coiled seminiferous tubules terminate within the rete testis, which in turn coalesces to form the ductuli efferentes. These ductuli efferentes conduct testicular fluid and spermatozoa into the head of the epididymis. The epididymis consists of a fragile single convoluted tubule that is 5-6 meters in length. The epididymis is divided into the head, body, and tail. The epididymis also serves as a reservoir or storage area for sperm. Prior to ejaculation peristalsis of the vas deferens and bladder neck occur under sympathetic nervous control. The major volume of the seminal fluid comes from the seminal vesicles and secondarily the prostate. The first portion of the ejaculate characteristically contains most of the spermatozoa and most of the prostatic secretions, while the second portion is composed primarily of seminal vesicle secretions and fewer spermatozoa.

Check Out My Other Info On About Pregnancy , IVF Info and In Vitro Fertilization