Topic 16.5A · Core
Sex Hormones in Humans
Testosterone and oestrogen each drive their own set of physical changes at puberty, but pairing them the wrong way round is an easy, avoidable error — hold the pairing exactly, and this section is straightforward.
What secondary sexual characteristics are
Secondary sexual characteristics are the physical changes associated with sexual maturity that develop at puberty — they are not the reproductive organs themselves, but the visible bodily changes that appear alongside sexual development.
Testosterone
Testosterone is produced mainly by the testes. During puberty it drives the development of male secondary sexual characteristics, including a deeper voice, increased facial and body hair, and increased muscle development.
Oestrogen
Oestrogen is produced mainly by the ovaries. During puberty it drives the development of female secondary sexual characteristics, including breast development and a widening of the hips.
Some puberty changes, such as body and pubic hair, develop under the influence of both hormones rather than belonging exclusively to one — so it’s worth resisting the temptation to treat every single puberty change as controlled by only testosterone or only oestrogen.
Where this leads next
In females, oestrogen’s role doesn’t stop at puberty — it goes on to become one of four interacting hormones that control a repeating monthly cycle of changes in the ovary and the uterus, covered in full on the menstrual cycle and its hormones.