Approximately 15% of all couples have difficulty achieving a pregnancy during their reproductive years. In about 50% of these couples, a male factor is involved, either alone or with a coinciding female factor. The spectrum of causes of male infertility is quite variable, as are the possible treatments. Fortunately, significant progress has been made in the past decade in both the diagnosis and treatment of these infertile couples. These advances have allowed for the successful correction of problems and the ultimate ability to establish a pregnancy for men who just a few years ago had little chance of having a biologic child of their own.
The testes are paired organs located within the scrotum, which is a multi-layered muscular regulation. The tests have two very important functions, and each of them is essential for normal male fertility:
- Production of testosterone
- Production of sperm
The testes are normally 4 to 5cm long, and they are each encased by a firm, fibrous capsule called the tunicaal buginea. Within this capsule, the seminification tubules are found. These tubules are very small structures containing Sertoli cells (support and nurturing cells for the sperm) and the germinal epithelium, the precursor cells that mature into spermatozoa. Along the course of normal seminiferous tubules , one finds sperm present at various stages of development, from the immature spermatogonium to the mature spermatozoon. Surrounding the seminiferous tubules are interstitial cells, which include the Leydig cells is to produce testosterone, which is essential for spermatogenesis.
The rete testis and efferent ductules are tubes that lead from the testis to the epididymis. it is through these tubes that sperm pass from the seminiferous tubules to their next destination, the epididymis. The epidiymis is a long, narrow duct, approximately 6 meters in length, which is coiled and housed beneath a fibrous sheath. The epididymis sits on the back of the testis, and it is divided into head, body and tail regions. Sperm undergo their final stages of maturation here and then proceed into the vas deferens. The vas deferens is a long tubular structure that arises from the tail of the epididymis and proceeds superiorly in the scrotum with the spermatic cord. The vas travels up the inguinal canal within the spermatic cord, diverges from the cord behind the abdominal wall, where it then proceeds to the pelvis, to an area behind the prostate. Near the prostate the vas merges with a lateral pouch like structure called the seminal vesicle. There are two seminal vesicles, each seminal vesicle is about 4 cm in length and contributes fructose to the seminal fluid. The seminal vesicle and vas deferens fuse to form the ejaculatory duct, which courses through the prostate to terminate in the urethra. During ejaculation, the seminal fluid, a combination of sperm, prostatic secretions, and seminal vesicle secretions, is expelled out the urethra.
The production of sperm that are capable of a pregnancy is a very complicated process. The purpose of sperm production is simple to create a mechanism by which the male's chromosomal material may be combined with that of a female partner to proceed an embryo. This process of active spermatogenesis begins at puberty and lasts, in healthy males, until death.
Sperm production in the testicle is under hormonal control, which is regulated but he hypothalamus and the pituitary gland in the brain. These hormonal actions are known as the hypothalamic-pituitary-gonadal (HPG) axis. The hypothalamus regulates the hormonal activity of the anterior pituitary gland by secreting gonadotropin-releasing hormone (GnRH), which in turn, controls the secretion of follicle stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. Under the influence of LH, the Leydig cells within the testes make testosterone, an essential cofactor in spermatogenesis. Under the influence of FSH, Sertoli cells within the testes facilitate the production of sperm by secreting various growth factors. From beginning to end, sperm production takes about 72 days. The first 50 days are spent in the testis and the last 22-24 days in the epididymis. In the epididymis, sperm both mature and gain motility. During sexual activity, motile sperm are ejaculated into the female reproductive tract and thus begin their journey to the fallopian tubes, the site of fertilization.
In the past, couples were instructed to initiate fertility workups only after at least one year of unsuccessful attempts. Often, the evaluation was limited to the female partner alone. This view has subsequently changed and couples are now encouraged to proceed with an evaluation when they first suspect a problem with their reproductive function. Issues such as patient anxiety and advanced material age are among the factors that have led to this new approach.
For the male patient, the work up should generally begin when the female partner evaluation is initiated. The important point, as mentioned earlier, is that a male factor is involved as many as 50% of fertile couples. Thus a delay in evaluation and diagnosis may ultimately impair the couples chance for achieving pregnancy.