Endocrine glands are ductless glands of the endocrine system that secrete their products, hormones directly into the blood. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands.

The pituitary gland is a tiny organ, the size of a pea, found at the base of the brain. As the “master gland” of the body, it produces many hormones that travel throughout the body, directing certain processes or stimulating other glands to produce other hormones.

ANF (atrial natriuretic factor) is secreted by the atrial walls of the heart. It is responsible for a decrease in blood pressure. When the blood pressure is increased, ANF which is secreted dilates the blood vessels causing a decrease in blood pressure.

Thomas Addison was the first person who showed the relation between the secretion of the adrenal gland and Addison’s disease named after him.

• Erythropoietin is a  peptide hormone produced primarily by juxtaglomerular cells of the kidney.
• Erythropoietin stimulates the bone marrow to produce more red blood cells.
• The resulting rise in red cells increases the oxygen-carrying capacity of the blood.
• As the prime regulator of red cell production, erythropoietin's major functions are to promote the development of red blood cells.
• Hence, Juxtaglomerular cells of kidney produce a peptide hormone called Erythropoietin.