Adrenal glands

Clinic

• Also known as suprarenal glands
• They are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol.
• Each gland has an outer cortex + an inner medulla.
• Outer cortex itself is divided into three main zones:
  1. Zona glomerulosa: Produces Aldosterone, helping in regulation of blood pressure and electrolyte balance.
  2. Zona fasciculata: Produces glucocorticoids (cortisol and cortisone)
  3. Zona reticularis: Produces androgens that are converted to fully functional sex hormones in the gonads and other target organs. The production of steroid hormones is called steroidogenesis, and involves a number of reactions and processes that take place in cortical cells.
• Inner medulla produces catecholamines, which function to produce a rapid response throughout the body in stress situations.

Clinical significance

Corticosteroid overproduction

• Cushing's syndrome: Obesity + Diabetes + Increased blood pressure + Hirsutism + Osteoporosis + Depression + Stretch marks in the skin (Progressive thinning)

• Primary aldosteronism: Caused by bilateral hyperplasia or Aldosterone-producing adenomas (Conn's syndrome).

Adrenal insufficiency

Deficiency of glucocorticoids. Diseases classified as

• Primary adrenal insufficiency (including Addison's disease and genetic causes) directly affect the adrenal cortex
• Secondary adrenal insufficiency. If a problem that affects the hypothalamic-pituitary-adrenal axis arises outside the gland.

Addison's disease

Its characteristic feature is skin hyperpigmentation Addison's disease refers to primary hypoadrenalism, which is a deficiency in glucocorticoid and mineralocorticoid production by the adrenal gland. In the Western world, Addison's disease is most commonly an autoimmune condition, in which the body produces antibodies against cells of the adrenal cortex. Worldwide, the disease is more frequently caused by infection, especially from tuberculosis. A distinctive feature of Addison's disease is hyperpigmentation of the skin, which presents with other nonspecific symptoms such as fatigue.

A complication seen in untreated Addison's disease and other types of primary adrenal insufficiency is the adrenal crisis, a medical emergency in which low glucocorticoid and mineralocorticoid levels result in hypovolemic shock and symptoms such as vomiting and fever. An adrenal crisis can progressively lead to stupor and coma. The management of adrenal crises includes the application of hydrocortisone injections.

Secondary adrenal insufficiency[edit]

In secondary adrenal insufficiency, a dysfunction of the hypothalamic-pituitary-adrenal axis leads to decreased stimulation of the adrenal cortex. Apart from suppression of the axis by glucocorticoid therapy, the most common cause of secondary adrenal insufficiency are tumors that affect the production of adrenocorticotropic hormone (ACTH) by the pituitary gland. This type of adrenal insufficiency usually does not affect the production of mineralocorticoids, which are under regulation of the renin–angiotensin system instead.

Congenital adrenal hyperplasia[edit]

Congenital adrenal hyperplasia is a congenital disease in which mutations of enzymes that produce steroid hormones result in a glucocorticoid deficiency and malfunction of the negative feedback loop of the HPA axis. In the HPA axis, cortisol (a glucocorticoid) inhibits the release of CRH and ACTH, hormones that in turn stimulate corticosteroid synthesis. As cortisol cannot be synthesized, these hormones are released in high quantities and stimulate production of other adrenal steroids instead. The most common form of congenital adrenal hyperplasia is due to 21-hydroxylase deficiency. 21-hydroxylase is necessary for production of both mineralocorticoids and glucocorticoids, but not androgens. Therefore, ACTH stimulation of the adrenal cortex induces the release of excessive amounts of adrenal androgens, which can lead to the development of ambiguous genitalia and secondary sex characteristics.

Adrenal tumors[edit]

Incidences and prognoses of adrenal tumors. Main article: Adrenal tumor

Adrenal tumors are commonly found as incidentalomas, unexpected asymptomatic tumors found during medical imaging. They are seen in around 3.4% of CT scans, and in most cases they are benign adenomas. Adrenal carcinomas are very rare, with an incidence of 1 case per million per year.

Pheochromocytomas are tumors of the adrenal medulla that arise from chromaffin cells. They can produce a variety of nonspecific symptoms, which include headaches, sweating, anxiety and palpitations. Common signs include hypertension and tachycardia. Surgery, especially adrenal laparoscopy, is the most common treatment for small pheochromocytomas.