Sex hormones in humans — Cambridge IGCSE Biology
Testosterone and oestrogen in puberty, the menstrual cycle, and how FSH, LH, oestrogen and progesterone control the cycle and pregnancy.
Revision notes
2 short notes, in the order of the specification. Each one 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.
The menstrual cycle is a series of changes in the ovaries and the lining of the uterus that repeats about every 28 days. Menstruation happens on days 1 to 5, the lining is repaired and thickens, and ovulation occurs around day 14. FSH matures an egg, LH causes ovulation, and oestrogen and progesterone build and maintain the lining.
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Quick check questions
Which hormone is made in the testes?
Show answer
Testosterone.
Name two secondary sexual characteristics that oestrogen causes in girls.
Show answer
Any two from: breast development, pubic and underarm hair, wider hips, start of the menstrual cycle.
What happens to the uterus lining during menstruation?
Show answer
It breaks down and is lost through the vagina with blood.
Supplement Which hormone causes ovulation?
Show answer
LH.
Supplement Name the organ that makes progesterone in pregnancy.
Show answer
The placenta.
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.
What does testosterone do at puberty?
Testosterone, made in the testes, causes the development of male secondary sexual characteristics at puberty. These include growth of facial, pubic and underarm hair, a deeper voice, muscle development, growth of the testes and penis, and the start of sperm production. Testosterone also regulates these characteristics once they have developed.
Written and checked against the Cambridge IGCSE Biology (0610) specification · Updated October 2026