Hormones in Infertility Treatment

Why hormones can help with infertility

For a pregnancy to begin naturally, an egg must mature and be released from an ovary. Sperm must then reach and fertilise it, usually in an oviduct. The fertilised egg divides to form an embryo, which must implant in the lining of the uterus.

Infertility means difficulty conceiving naturally after a long period of trying. Treatment depends on which part of reproduction is not working. Hormones can help when the problem is insufficient stimulation of the ovaries, but they cannot remove a physical blockage in an oviduct.

Hormones are chemical messengers carried in the blood to target organs. Normally, the pituitary gland releases FSH, which stimulates ovarian follicles so that eggs mature, and LH, which triggers ovulation. A follicle is a structure in an ovary containing a developing egg. Too little FSH can mean that an egg does not mature; too little LH can mean that a mature egg is not released.

Fertility drugs support natural conception

Fertility treatment can supply hormones that the body is not producing in sufficient amounts. FSH is given to stimulate eggs to mature, and LH can be given to trigger their release from the ovaries.

If ovulation is restored and there are no other barriers to conception, fertilisation can take place inside the body after intercourse. The drugs do not fertilise the egg themselves: they help make an egg available for fertilisation.

Hormone treatment may stimulate several follicles rather than just one. If several eggs are released and fertilised, twins or triplets may develop. Multiple pregnancies carry greater risks for the mother and babies, so releasing more eggs is not simply an advantage.

IVF moves fertilisation outside the body

In vitro fertilisation, or IVF, is another way of treating infertility. It can help when natural conception is unsuccessful, including when a blocked oviduct prevents sperm and egg from meeting. IVF bypasses this meeting place by bringing eggs and sperm together in a laboratory.

The main stages are:

1. Hormone treatment: FSH and LH are used to control ovarian activity, with FSH stimulating several eggs to mature. Having several eggs available increases the opportunity to obtain embryos.
2. Egg collection: mature eggs are collected directly from the ovaries using a fine needle.
3. Fertilisation: the collected eggs are mixed with sperm in a laboratory dish.
4. Embryo development: fertilised eggs are kept under suitable conditions and allowed to divide into embryos.
5. Embryo transfer: a selected embryo, or sometimes more than one, is transferred into the uterus. If an embryo implants in the uterine lining, a pregnancy can develop.

Progesterone may also be given to maintain the uterine lining and support implantation. Its role is different from FSH and LH: it supports the lining rather than stimulating egg maturation or release.

What treatment can and cannot achieve

Both fertility drugs and IVF use hormones to influence the reproductive cycle. The key difference is where fertilisation happens: inside the body with fertility drugs alone, but outside the body with IVF.

Neither treatment guarantees a pregnancy. With IVF, eggs may not fertilise or an embryo may not implant. Hormone treatment can cause side effects, and transferring more than one embryo increases the possibility of a multiple pregnancy. IVF offers a chance of pregnancy, rather than a certain outcome.