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 made from cholesterol.
The adrenal cortex produces three hormones:
Adrenocorticotropic hormone (ACTH), secreted by the anterior pituitary gland, primarily affects release of glucocorticoids and adrenal androgens by the adrenal gland and, to a much 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.
Commonly, overproduction of aldosterone can occur, which causes a condition known as primary 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. Some studies have suggested that hyperaldosteronism may account for up to 5% of all people with high blood pressure and an even higher proportion of those who have treatment-resistant hypertension.
In rare cases, the adrenal glands can become either overactive or underactive. The two main glucocorticoid-related disorders resulting from these are Cushing's syndrome and Addison's disease, respectively.
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. 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.
Overproduction of androgens is also very 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 2018