Ovulation and hormones
>About one-third of female infertility is caused by failure to release an egg (ovulate). This is usually due to hormonal problems, but occasionally a woman's ovaries are damaged or, more rarely, have run out of eggs.
Failure to ovulate
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In a woman with a normal ovarian cycle the hormones produced by the pituitary gland and the ovary are responsible for the healthy growth and maintenance of an egg. In many cases of infertility, too little of one or too much of the other hormone may be present. For example, at mid-cycle the hypothalamus should stimulate the pituitary gland to release massive amounts of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to bring about ovulation, but in 20 per cent of cases it fails to do so. Although there may be some LH and FSH, there's not enough for ovulation.
Alternatively, the pituitary gland may be damaged or malfunctioning, and either produce too little LH and FSH or none at all. Or, as a result of too much LH stimulation and not enough FSH, the ovaries may become polycystic and have difficulties producing mature eggs.
Problems caused by abnormal levels of hormones are often treated by fertility drugs. For 90 per cent of women whose infertility is caused by hormonal problems, modern drug therapy can bring about regular ovulation. Unfortunately, for reasons unknown, only about 65 per cent of these women will actually get pregnant.
Hormonal imbalance
Hormones may interfere with conception in other ways than influencing ovulation. For example, a fertilized egg needs progesterone in order to survive. If too little progesterone is produced or it's produced for too short a time, the egg may not survive. Known as inadequate luteal phase, this condition can be treated with drugs.
Hyperprolactinaemia
In this quite common condition the pituitary gland produces too much of the hormone responsible for milk production. Often, there's no apparent reason why this happens. The condition can sometimes be caused by a small benign tumour developing on the pituitary gland, called a prolactinoma. This leads to low levels of LH and FSH, which causes infrequent or absent periods in women and lowered sperm production in men.
Posted 16.11.2010
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