Fertility

In order to understand the causes of infertility and the role modern infertility treatment plays in assisting conception, it is useful to look at the natural process - a woman's ovulatory cycle and the production of sperm in the male - and the hormones that play a major role in those processes.

The gonadotropins are hormones that primarily affect the ovaries and the testes. They regulate the development and hormone-secreting functions of these organs and contribute to the production of sperm in the male and to the development and maturation of eggs (oocytes) in the female.

Three gonadotropins are essential to reproduction: human follicle stimulating hormone (hFSH), human luteinizing hormone (hLH) and human chorionic gonadotropin (hCG). FSH and LH are secreted by the pituitary gland situated beneath the brain. Their secretion is controlled by another hormone, the gonadotropin- releasing hormone (GnRH) produced by the hypothalamus. hCG is primarily produced by the placenta following successful implantation, and plays a role in maintaining pregnancy.

Androgen is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates by binding to androgen receptors. This includes the activity of the accessory male sex organs and development of male secondary sex characteristics. Androgens, which were first discovered in 1936, are also called androgenic hormones or testoids. Androgens are also the original anabolic steroids.

They are the precursors of all estrogens, the female sex hormones. The primary and most well-known androgen is testosterone. A subset of androgens, adrenal androgens, includes any of the 19-carbon steroids synthesized by the adrenal cortex, the outer portion of the adrenal gland (zonula reticularis - innermost region of the adrenal cortex), that function as weak steroids or steroid precursors, including dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEA-S), and androstenedione.