Sex hormones in humans
Puberty
- At puberty, sex hormones bring on secondary sexual characteristics.
- Examples: body hair, a deeper voice in boys, breasts in girls.
- Testosterone does this in boys; oestrogen does it in girls.
Practice
The hormone that causes secondary sexual characteristics in boys is:
Testosterone drives male development at puberty; oestrogen does so in girls.
The menstrual cycle
- The cycle (about 28 days) prepares the uterus for a possible pregnancy:
- the lining of the uterus thickens,
- around day 14 an ovary releases an egg (ovulation),
- if the egg is not fertilised, the lining breaks down and leaves the body (a period); the cycle restarts.
- (Supplement) Four hormones: FSH (egg matures), LH (triggers ovulation), oestrogen (thickens lining), progesterone (keeps lining thick).
Practice
Ovulation (release of an egg) happens around:
An ovary releases an egg around day 14, halfway through the ~28-day cycle.
Practice
Match each cycle hormone to its job.
FSH matures an egg, LH triggers ovulation, oestrogen repairs and thickens the lining (progesterone keeps it thick).
You've got it
Key idea
- puberty: testosterone (boys) / oestrogen (girls) → secondary sexual characteristics
- menstrual cycle ≈ 28 days: lining thickens → ovulation (day 14) → period if no fertilisation
- (Supplement) FSH, LH, oestrogen, progesterone control the cycle