4.5.3.4 - Hormones in Human Reproduction

Puberty and reproductive hormones

At puberty, reproductive hormones cause secondary sex characteristics to develop. Secondary sex characteristics are features that develop during puberty but are not the reproductive organs themselves, such as changes in body hair, voice, breasts, hips and body shape.

Oestrogen is the main female reproductive hormone in this specification point. It is produced in the ovaries. Testosterone is the main male reproductive hormone in this specification point. It is produced by the testes and stimulates sperm production.

The words main female and main male do not mean that only one sex ever has that hormone. They are GCSE boundary phrases about the main reproductive role you must know for AQA.

Ovulation and the menstrual cycle

At puberty, eggs begin to mature in the ovaries. Approximately every 28 days, one egg is released from an ovary. This release of an egg is called ovulation.

The menstrual cycle is a repeating cycle of changes involving the ovaries and the uterus lining. A 28-day cycle is the usual GCSE model and an average; real cycles can be shorter or longer. For AQA answers, approximately every 28 days is safer than exactly every 28 days.

The uterus lining matters because it must be maintained during the cycle. Oestrogen and progesterone are the named hormones in this lesson that are involved in maintaining the uterus lining.

Hormone roles in the menstrual cycle

Several hormones are involved in the menstrual cycle. For all students, the safest first step is to know the direct role of each hormone.

Notice the difference between maturation and release. FSH causes the egg to mature in the ovary. LH stimulates the release of the egg from the ovary. Mixing those two roles is a common way to lose a simple mark.

The abbreviations are also worth learning exactly. FSH stands for follicle stimulating hormone. LH stands for luteinising hormone.

Hormone interactions

This section is Higher Tier only. Higher Tier students must explain how FSH, oestrogen, LH and progesterone interact to control the menstrual cycle. That means writing a sequence of cause-and-effect links, not just listing four hormone definitions.

Early in the cycle, FSH causes an egg to mature in the ovary. As the egg matures, oestrogen levels rise. Oestrogen helps maintain and rebuild the uterus lining. Rising oestrogen also affects the pituitary gland: it stimulates the release of LH and inhibits further release of FSH.

The rise in LH is important because LH stimulates ovulation, the release of the egg. After ovulation, progesterone levels rise. Progesterone maintains the uterus lining and inhibits the release of FSH and LH. If progesterone later falls, the uterus lining is no longer maintained and the cycle can begin again.

You can write the Higher Tier sequence like this: