Testosterone, oestrogen and puberty

Reproduction · Sex hormones in humans · note 1 of 2

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Testosterone, oestrogen and pubertySpec 16.5.1

In short

Puberty is the stage when the body changes and becomes able to reproduce, controlled by sex hormones. Testosterone, made in the testes, and oestrogen, made in the ovaries, cause the development of secondary sexual characteristics. In boys these include facial hair and a deeper voice; in girls, breast development, wider hips and the start of the menstrual cycle.

At puberty, the body changes and becomes able to reproduce. These changes are controlled by sex hormones. Testosterone is made in the testes. Oestrogen is made in the ovaries.

The hormones cause the development of secondary sexual characteristics. They also regulate them once they have developed.

Secondary sexual characteristics at puberty
Hormone	Secondary sexual characteristics
Testosterone (boys)	Growth of facial hair, pubic hair and underarm hair; voice deepens; muscles develop; testes and penis grow; sperm production begins
Oestrogen (girls)	Breasts develop; pubic hair and underarm hair grow; hips widen; the menstrual cycle begins and eggs are released from the ovaries

Exam tip:

Name the hormone and the organ that makes it: testosterone from the testes, oestrogen from the ovaries. Do not say 'male hormone' on its own.

Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026

Frequently asked questions

What does FSH do in the menstrual cycle?

Supplement FSH causes an egg cell to mature in the ovary and stimulates the ovary to make oestrogen. It is made in the pituitary gland. As oestrogen rises, it inhibits FSH and stimulates the release of LH, which causes ovulation around day 14. Progesterone also inhibits FSH later in the cycle.

What happens on day 14 of the menstrual cycle?

Around day 14 of the menstrual cycle, ovulation happens: an egg cell is released from an ovary into the oviduct. Before this, the egg matures in the ovary while the uterus lining is repaired and thickens. Afterwards the lining stays thick, ready for an embryo, until it breaks down if there is no pregnancy.

What does progesterone do in pregnancy?

Supplement In pregnancy, progesterone made by the placenta keeps the uterus lining in place, so there is no menstruation. High progesterone also inhibits FSH and LH, so no more egg cells mature or are released during pregnancy. If there is no pregnancy, progesterone falls and the uterus lining breaks down.

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