Reproductive hormones

A hormone is a chemical substance produced by a gland. Hormones are carried by the blood around the body but alter the activity of specific target organs only.

Different hormones affect different organs or cells.

Hormones and the glands that produce them in the human bodyThe location of the endocrine glands in the body - the main hormones involved in reproduction are released by the pituitary gland, ovaries and testes


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.

During puberty, reproductive hormones cause secondary sex characteristics to develop:

  • Testosterone - produced by the testes - is the main male reproductive hormone and it stimulates sperm production.
  • Oestrogen - produced by the ovaries - is the main female reproductive hormone. At puberty, eggs begin to mature and one is released approximately every 28 days. This is called ovulation.

Changes during puberty

A variety of changes happen to boys and girls 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