Puberty and secondary sexual characteristicsSpec 3.13
In short
Secondary sexual characteristics are features that develop at puberty but are not directly part of the reproductive organs. In girls, oestrogen from the ovaries causes breasts to develop, hips to widen and the menstrual cycle to begin. In boys, testosterone from the testes causes facial hair, a deeper voice, muscle development and sperm production.
At puberty, the sex hormones cause the body to develop secondary sexual characteristics. These are the features that develop at puberty, which are not directly part of the reproductive organs. In girls, the hormone is oestrogen, made by the ovaries. In boys, it is testosterone, made by the testes.
| Hormone | Made by | Effects at puberty |
|---|---|---|
| Oestrogen | Ovaries | Breasts develop. Hips widen. Pubic and underarm hair grow. The menstrual cycle begins |
| Testosterone | Testes | Facial hair grows. The voice deepens. Muscles develop and shoulders broaden. Pubic and underarm hair grow. Sperm production begins |
Name the hormone and the gland that makes it, then give the effect. For example: ‘testosterone from the testes makes the voice deepen’.
Quick check
Where are sperm made?
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In the testes.
What does oestrogen do in the menstrual cycle?
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It repairs and builds up the lining of the uterus.
What does progesterone do in the menstrual cycle?
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It maintains the lining of the uterus.
Biology only Which hormone causes ovulation?
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LH.
How does amniotic fluid protect the embryo?
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It absorbs shocks and cushions the embryo against knocks.
Written and checked against the Edexcel IGCSE Biology (4BI1) specification · Updated October 2026