Function: Puberty

Puberty is a period of rapid growth and physical change, during which adolescents become sexually mature. The age at which puberty begins and the rate of growth are influenced by genetics, general health, and weight. Puberty begins when the pituitary gland, located at the base of the brain, secretes hormones that stimulate the production of sex hormones. Within about 2 years of the start of puberty, sexual reproduction is possible, but it takes longer for adolescents to become mature enough emotionally for adult relationships.

Changes in girls during puberty

In girls, puberty begins between the ages of 10 and 14, when luteinizing hormone (LH) and follicle-stimulating hormone (FSH) stimulate the ovaries to secrete the sex hormones oestrogen and progesterone. These hormones prompt physical changes and, later, stimulate ovulation and menstruation.

The rise in oestrogen at puberty

The oestrogen level rises sharply between about 11 and 14. After this period, it levels out until the menopause, when it decreases.

Magnified breast tissue

At puberty, the breasts start to enlarge as they develop the milk glands and ducts that supply milk after a baby is born.


Late in puberty, ovulation begins; every month an egg is released from the ovary (as shown here) and travels to the uterus.

Changes in boys during puberty

In boys, puberty usually begins between the ages of about 12and 15, when the pituitary gland starts to secrete the hormones LH and FSH. These hormones stimulate the testes to secrete the male sex hormone testosterone, which prompts physical changes and, later, sperm production and increased sex drive.

The rise in testosterone at puberty

The testosterone level rises sharply between about 13 and 16. After this period, it levels out until old age, when it gradually decreases.

Facial hair

Hair on the face is part of the typical male pattern of hair growth triggered by increasing levels of testosterone.

Cross section of testis tissue

In each testis, there are about 1,000 tubules. During puberty, these tubules begin to produce sperm cells.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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