Sexual characteristics which develop in mature boys and girls are called secondary sexual characters. These changes are controlled by hormones.

Hormones released by the reproductive organs like testes and ovaries and involved in the development of secondary sexual characteristics are called sex hormones. The two common sex hormones are testosterone and estrogen.

Secondary sexual characteristics in males are:

(i) Hair grow on the face in the form of moustache and beard, and on the chest.

(ii) Testis grow and starts producing sperms in males.

Secondary sexual characteristics in females are:

(i) Milk secreting glands or mammary glands develop inside the breasts.

(ii) Initiation of menstruation.

(iii) Ovary enlarges and starts producing matured eggs.