Drugs that are used to treat couples who are unable to conceive
Human chorionic gonadotrophin
Drugs can be used to help a woman to become pregnant when a couple’s inability to conceive is caused by a hormonal imbalance in either the male or the female (see Infertility). For conception to occur, all the following steps must take place: ovulation (the release of a mature egg by an ovary), fertilization of the egg by a sperm, transport of the fertilized egg along the fallopian tube to the uterus, and implantation of the egg in the uterus lining.
Fertility is influenced by hormones produced in the brain by the hypothalamus and the pituitary gland. The hypothalamus secretes gonadotrophin-releasing hormone, which regulates the release of gonadotrophin hormones from the pituitary gland. The main gonadotrophin hormones are known as follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These hormones control fertility. In females, FSH stimulates the ripening of eggs, and LH triggers ovulation (release of the egg). In males, FSH and LH regulate sperm production. An imbalance or deficiency of these hormones may lead to infertility. In such cases, drugs may be used to stimulate the ovaries to produce eggs, or less commonly, to stimulate a man to produce more sperm.
In women, drugs may also be used to stimulate the ovaries to produce more eggs than normal as part of techniques called assisted conception, such as in-vitro fertilization (IVF), gamete intrafallopian transfer (GIFT), and zygote intrafallopian transfer (ZIFT). These techniques are infertility treatments that involve mixing eggs and sperm outside the body.
Women who are having treatment with fertility drugs are monitored using blood tests and ultrasound scanning because there is a small risk that the ovaries may become over-stimulated, which can be a life-threatening condition. Symptoms of overstimulation can include nausea, vomiting, and abdominal pain and swelling. Infertility treatment also increases the likelihood of multiple pregnancy.
Treatments for infertility may not be effective immediately. These treatments often need to be continued for several months to increase the likelihood of conception.
What are the types?
In females, low levels of FSH and LH can be boosted by using an anti-oestrogen (also known as an oestrogen antagonist). Synthetic gonadotrophin hormones may also be given to influence fertility directly in both males and females. A gonadorelin analogue may sometimes be given in conjunction with gonadotrophin drugs in the treatment of female infertility.
The naturally occurring hormone oestrogen suppresses the production of FSH and LH. Treatment with an oral anti-oestrogen, such as clomifene or tamoxifen, blocks this effect and stimulates the pituitary gland to produce more FSH and LH, thereby encouraging ovulation.
Clomifene may cause side effects such as visual disturbances, headache, nausea, hot flushes, breast tenderness, and abdominal pain. Ovarian cysts occasionally develop, but may shrink when the dose is reduced. If you take the drug for longer than 6 months, there may be an increased risk of developing cancer of the ovary. The drug may also cause multiple pregnancies.
Tamoxifen may cause side effects such as menstrual irregularities, and may increase the risk of thromboembolism and uterine cancer (see Sex hormones and related drugs).
Men and women who produce very low levels of FSH or LH may be given injections of synthetic FSH, such as follitropin, or human chorionic gonadotrophin (HCG), a hormone that mimics the action of LH. Gonadotrophins may also be used if treatment with the anti-oestrogen drug clomifene is unsuccessful. These synthetic hormones can be used to stimulate the production of several eggs in women undergoing assisted conception. In men, they can be used to increase sperm production. Several monthly courses may be needed. Possible side effects include headaches, tiredness, and mood changes. In men, the breasts may enlarge.
These drugs are sometimes given to women undergoing assisted conception who are also being given synthetic gonadotrophins. When given intermittently, gonadorelin analogues stimulate the release of FSH and LH. However, when taken continuously, they block the effects of natural gonadotrophin-releasing hormone, thus reducing the production of FSH and LH. Blocking the production of natural gonadotrophins makes it easier for doctors to control the action of synthetic gonadotrophins. Gonadorelin analogues are given by injection or as a nasal spray. Side effects include hot flushes, itching, loss of libido, nausea, and vomiting.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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