Sex hormones are the hormones that control the development of secondary sexual characteristics and also regulate the proper functioning of the sex organs. They are named so because they are produced in both males and females by the respective sex organs under the influence of the pituitary gland. Functions of sex hormones: 

→ Testosterone: This hormone secreted by the testes brings about secondary sex characters in boys such as the growth of a beard, the voice becoming hoarse, development of reproductive organs, etc. 

→ Oestrogen: This hormone secreted by the ovaries is responsible for the development of secondary sexual characters in females such as the enlargement of breasts, development of female reproductive organs, etc.

The changes which occur at adolescence are controlled by hormones. Hormones chemical substances.These are secretions from endocrine glands or endocrine system. The male hormone or testosterone begins to be released by the testes at the onset of puberty. For example, the growth of facial hair. Once puberty is reached in girls, ovaries begin to produce the female hormone or estrogen which makes the breasts develop. Milk secreting glands or mammary glands develop inside the breasts. The production of thes​​​​​​​e hormones is under the control of another hormones secreted from an endocrine gland called pituitary gland.