Adrenal glands, also called suprarenal glands, are small, triangular glands located on top of each kidney (one on each side) and measuring about one-half inch in height and 3 inches in length. The adrenal gland consists of two parts: the outer region called the adrenal cortex and the inner region called the adrenal medulla.
Function of the adrenal glands
The two parts of the adrenal glands, i.e. the adrenal cortex and the adrenal medulla perform separate functions. The adrenal cortex produces glucocorticoids (i.e., cortisol), mineralocorticoids (i.e. aldosterone) and androgens (DHEA and androstendione). Cortisol, a hormone essential for life has important effects on heart, blood pressure, immunity, metabolism, bone and nervous system. Both cortisol deficiency and overproduction will cause significant problems. Aldosterone is necessary for fluid and electrolyte (salt) balance and its excess may have clinical consequences. The adrenal androgen hormones cause problems mainly when overproduction occurs in women. The medulla is responsible for producing epinephrine and norepinephrine (adrenaline) with effects on blood pressure, heart and metabolism. Excess of medulla function will cause problems.
Regulation of the adrenal gland hormones
Cortisol is secreted by the adrenal glands in response to circadian and stress-induced stimulation by adrenocorticotropic hormone (ACTH) secreted by the pituitary gland. The pituitary gland is the "master" gland of the endocrine system, situated at the base of the brain. Aldosterone secretion is regulated by a system called renin-angiotensin and by potassium concentration, whereas pituitary gland is only a minor modulator.
In summary, the adrenal glands disorders consist of: adrenal insufficiency (deficiency in secretion, especially cortisol), adrenal hormone overproduction mainly caused by adrenal tumors (pheochromocytoma, aldosteronoma, androgen-producing tumors) and other adrenal tumors without hormone overproduction.