7.8 - Fertility treatment

7.8 - Higher: hormones in fertility treatment

Higher-only (7.8). Assisted Reproductive Technology (ART) uses medical treatment to increase the chance of pregnancy. Clomifene therapy and in vitro fertilisation (IVF) both use the hormone-control system, but they do so in different ways.

Recall that FSH stimulates an ovarian follicle and its egg to mature, while an LH surge triggers ovulation. Oestrogen and progesterone also help control the uterus lining. These normal hormone responses are the starting point for fertility treatment.

Clomifene therapy

Clomifene is a fertility drug, not one of the four menstrual-cycle hormones. It reduces the effect of oestrogen feedback on the brain. The pituitary responds by releasing more FSH and LH: more FSH increases the chance that a follicle and egg mature, while more LH increases the chance of ovulation. Clomifene can therefore help when ovulation is irregular or absent; fertilisation, if it occurs, still happens inside the reproductive system. NHS: clomifene and hormone release.

7.8 - Hormones through an IVF cycle

Higher only.

In vitro means outside the body. In IVF, fertilisation is attempted in a laboratory before an embryo is transferred to the uterus. In contrast, clomifene supports ovulation and leaves fertilisation to occur inside the reproductive system. The choice depends on the cause of infertility: stimulating ovulation alone cannot bypass blocked oviducts.

A stimulated IVF cycle follows this route:

1. FSH is given to stimulate several follicles and eggs to mature rather than just one. Medicines can also control the natural cycle to prevent premature ovulation. This provides several eggs that could be collected and fertilised.
2. A timed hormone trigger, commonly hCG with an LH-like action, completes egg maturation. The eggs are then collected from the ovaries before they are released naturally.
3. The eggs are mixed with sperm in a laboratory, where fertilisation may occur.
4. A fertilised egg divides to form an embryo.
5. Progesterone can be supplied to support the uterus lining. An embryo is transferred to the uterus, where it may implant. Transfer and implantation are different events: placing an embryo in the uterus does not guarantee that it will attach or develop.