A hormone is a substance produced by an endocrine gland in the body and secreted into the bloodstream, from where it is transported to other parts of the body to perform its function in different organs and tissues.
Specifically, the function of hormones is to regulate physiological processes, for example, by activating or inhibiting different metabolic pathways.
There are many types of hormones and one of the most important is the sex hormones that regulate the functioning of the reproductive system. Sex hormones can be secreted by the gonads (eggs and testicles), the adrenal glands and the placenta in case of pregnancy. Its functions include controlling the menstrual cycle of the woman, controlling the spermatogenesis of the man, maintaining active secondary sexual characteristics, etc..