Puberty is the stage in life when a child's body develops into an adult's body. The changes take place gradually, usually between the ages of 10 and 16.

Changes occur at puberty because of hormones:

  • testosterone - produced by the testes - controls the development of male secondary sexual characteristics
  • oestrogen - produced by the ovaries - controls the development of female secondary sexual characteristics

Changes during puberty

Boys onlyBoys and girlsGirls only
Voice breaksPubic hair growsVoice deepens gradually
Hair grows on face and bodyUnderarm hair growsHips get wider
Body becomes more muscularSexual organs grow and developBreasts develop
Testes start to produce sperm cellsOvaries start to release egg cells - menstruation starts
X axis: age 0-18 (years). Y axis: height (cm) up to 190 cm. Height of boys and girls similar until aged 10 when girls become taller. At age 14 boys start to become taller than girls. Boys and girls grow at different rates

The menstrual cycle

The menstrual cycle is a recurring process which takes around 28 days. During the process, the lining of the uterus is prepared for pregnancy. If pregnancy does not happen, the lining is then shed. This is known as menstruation.

Hormones in the menstrual cycle

Several hormones control this cycle – for example, they are involved in controlling the release of an egg each month from an ovary, and changing the thickness of the uterus lining.

FSH (follicle stimulating hormone)Pituitary glandCauses an egg to mature in an ovary. Stimulates the ovaries to release oestrogen
OestrogenOvariesStops FSH being produced (so that only one egg matures in a cycle). Repairs and thickens the uterus lining. Stimulates the pituitary gland to release LH.
LH (luteinising hormone)Pituitary glandTriggers ovulation (the release of a mature egg)
ProgesteroneOvariesMaintains the lining of the uterus during the middle part of the menstrual cycle and during pregnancy.
Hormone levels over the menstrual cycle.  Levels rise between day seven and ten, as they begin to fall the egg is released at day 14. They then stabilise for the rest of the menstrual cycle. Hormone levels during the menstrual cycle

If a woman becomes pregnant, the placenta produces progesterone. This maintains the lining of the uterus during pregnancy and means that menstruation does not happen.