The gonads (testes in males and ovaries in females) are responsible for the production of gonadal/steroid hormones. The gonads, also called sex glands, are activated during puberty by the hormones secreted by the pituitary gland. After this, they begin to produce sex hormones and sex cells.

The most important steroid hormone secreted by the ovaries is estrogen, which controls the development of female secondary sexual characteristics. Similarly, in boys, testosterone produced by the testes controls the development of male secondary sexual characteristics, including muscle growth. This is the reason why artificial male hormones are used as doping agents. However, both sexes secrete both hormones, and the relative amount of both hormones in relation to each other is important.

In addition to sexual development, sex hormones affect the individual's height. There are also major changes in the frontal lobe of the brain, affecting a person's mental development.

Gonadal hormones

Endocrine gland	Hormone	Effects
ovaries	estrogen	Development of secondary sexual characteristics of a woman. Menstrual cycle, maintenance of uterine and mammary gland function.
ovaries	progesterone	Menstrual cycle and maintenance of pregnancy
testes	testosterone	Development of secondary sexual characteristics of a man. Sperm formation. Accelerates metabolism (anabolism). (Testosterone is also produced in the adrenal glands and in the ovaries).