Biology - Fertility

There are several chemical substances called hormones and they each have a different effect on us. Many processes within the human body are coordinated by hormones. They are secreted by glands and are usually transported to their target organs by the bloodstream.

Hormones regulate the functions of many organs and cells. For example, the monthly release of an egg from a woman’s ovaries and the changes in the thickness of the lining of her womb are controlled by hormones secreted by the pituitary gland and by the ovaries.

Several hormones are involved in the menstrual cycle of a woman. Hormones are involved in promoting the release of an egg:

• Follicle stimulating hormone (abbreviated to FSH) is secreted by the pituitary gland and causes eggs to mature in the ovaries.
• FSH also stimulates the ovaries to produce hormones including estrogen.
• As estrogen levels increase, it inhibits production of FSH.
• Luteinising hormone (abbreviated to LH) stimulates the release of eggs from the ovary.

Human fertility is controlled by hormones. This means that knowledge of hormones can be used to decide to increase, or reduce, the chances of fertilization and pregnancy. Some women have levels of FSH and LH that are too low to stimulate egg production. Giving them a 'fertility drug' has the effect of stimulating their eggs to mature. Oral contraceptives contain hormones (estrogen and progesterone) that inhibit the production of FSH so that no eggs mature.