The endocrine system consists of a group of organs (sometimes referred to as endocrine glands) whose main function is the production and secretion of hormones directly into the bloodstream. Hormones serve as messengers to coordinate the activities of different parts of the body.
Hormones secreted from the endocrine glands (endocrine glands) are transmitted directly through the blood or lymph to the target tissues. Once the hormone is recognized by the tissue a biological action occurs. The action of some hormones may begin immediately within a few seconds (epinephrine, glucagon), and the action of others may begin after a few hours or days (growth hormone, aldosterone).
The most important organs of the endocrine system are the hypothalamus, pituitary gland, thyroid gland, parathyroid glands, islets of the pancreas, adrenal glands, testes and ovaries (ovaries). During pregnancy as an endocrine gland, it acts in addition to its other functions and the placenta.