Each adrenal gland is composed of two distinct parts: the outer part called the adrenal cortex and the inner adrenal medulla. The adrenal glands secrete different hormones which act as 'chemical messengers'. These hormones travel in the bloodstream and act on various body tissues to enable them to function correctly. All adrenocortical hormones are steroid compounds derived from cholesterol.
The adrenal cortex produces three hormones:
Adrenocorticotropic hormone (ACTH) secreted by the anterior pituitary primarily affects release of glucocorticoids and adrenal androgens by the adrenal and to a lesser extent, also stimulates aldosterone release.
The adrenal medulla produces catecholamines:
Catecholamines include adrenaline, noradrenaline and small amounts of dopamine – these hormones are responsible for all the physiological characteristics of the stress response, the so called 'fight or flight' response.
Cushing's syndrome is due to overactive adrenal glands from excessive production of cortisol. The clinical findings include thinning and bruising of the skin, obesity, diabetes, psychiatric disturbances, high blood pressure, muscle weakness, osteoporosis, excessive facial hair and irregular periods in women. It can result in growth failure in children. Patients with cortisol excess also have impaired wound healing and an increased susceptibility to infection.
Addison's disease or adrenal insufficiency is due to underactive adrenal glands associated with lack of hormones. Adrenal insufficiency may be acute or chronic. Acute adrenal insufficiency results when an acute stress is superimposed on chronic adrenal insufficiency of any type. Symptoms of chronic adrenal insufficiency include low blood pressure, fatigue, weight loss, anorexia, nausea, vomiting, abdominal pain, salt craving and low blood sugar. Skin and mucous membranes may show increased pigmentation. The loss of secondary sex characteristics is seen only in women with the disease. Acute adrenal insufficiency is a medical emergency and must be identified and promptly treated. The hallmarks of acute adrenal insufficiency are circulatory collapse with abdominal pain and low blood sugar.
Rarely, overproduction of aldosterone can occur, which causes a condition known as hyperaldosteronism. This causes high blood pressure, which is resistant to conventional blood pressure control tablets, and salt disturbances. High blood pressure may cause headaches and visual problems.
Overproduction of androgens is also rare but may result in excessive hair growth and menstrual period disturbances.
Tumours of the adrenal gland are mostly benign and do not result in over or underproduction of adrenal hormones. Most tumours are discovered incidentally when people undergo scans for various other reasons. Adrenal cancer is very rare. Adrenal tumours may require surgery if they are large or overproduce hormones.
The treatment of each disorder varies according to the specific cause. Patients with any concerns about these conditions should seek advice from their doctor.
Last reviewed: Jan 2015