IGCSE Biology / Chemical coordination
Testosterone, oestrogen and puberty revision notes
Edexcel International GCSE Biology (4BI1), chapter 7: Chemical coordination, specification point 2.94, 3.13. Free lesson.
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Testosterone and oestrogen are sex hormones that cause changes during puberty. Knowing where they are made, what they do and how their release is triggered helps you explain the development of secondary sexual characteristics.
Where the sex hormones are made
The testes make testosterone, while the ovaries make oestrogen. These hormones cause different changes during puberty. Testosterone is made in the testes. Oestrogen is made in the ovaries.
What testosterone and oestrogen do
Both hormones cause pubic and underarm hair to grow. Other changes differ. Testosterone causes changes such as a deeper voice, while oestrogen causes breasts to develop and hips to widen. Testosterone causes facial and body hair to grow. It makes the larynx, or voice box, grow, so the voice deepens. It also increases muscle development and broadens the shoulders. Oestrogen causes breasts to develop and hips to widen. Testosterone starts sperm production. Oestrogen starts the menstrual cycle and ovulation.
Primary and secondary characteristics
The changes caused by sex hormones at puberty are called secondary sexual characteristics. They develop over several years. In contrast, primary sexual characteristics are the reproductive organs, which are present from birth. Primary characteristics: reproductive organs present from birth. Secondary characteristics: changes that develop at puberty.
How puberty is triggered
The brain starts it; the gonads carry it out. The hypothalamus signals the pituitary gland, which releases hormones into the blood. These act on the testes or ovaries, prompting them to make the sex hormones that cause secondary characteristics to develop.
Why puberty changes take time
Hormone levels rise gradually rather than jumping suddenly. The changes involve tissue growth, which takes time. Hormonal effects are slow and long-lasting by their nature, unlike nervous responses.