2. Adrenal glands

Anatomy of adrenal glands and their function

Inverted Y-shaped glands. Mediate stress response by releasing cortisol and catecholamines. Secondary sex hormone synthesis and BP regulation (aldosterone).

2 distinct components: medulla derived from neural crest, cortex derived from mesothelium

Often asymmetric, with left gland thicker than the right!

Adrenal cortex histology

Peripheral portion. Composed of 3 layers that synthesize distinct hormones derived from cholesterol.

Z. glomerulosa, most spfc: aldosterone

Z. fasciculata: Gl.cortico.steroids, response to ACTH

Z. reticulari, deepest: androgens

Adrenal tumors that can be diagnosed on imaging

Adrenal hyperplasia, adenoma, cortical carcinoma.

Adrenal medulla function

Innermost portion. Cathercolamine production (NE and E, derived from tyrosine)

Adrenal medulla masses

Pheochromocytomas, neuroblastic tumors (ganglioneuroma, ganglioneuroblastoma, neuroblastoma). Neuroblastoma is the most common extracranial solid tumor of childhood.

Biochemical approach to adrenal lesions

Divided into hyper- and hypofunctioning processes. Most incidentally detected adrenal lesions are not hyperfunctioning.

Adrenal hyperfunction

1. Cushing S: excess circulating cortisol by exogenous administration or endogenous production. Endogenous production may be central/pituitary (Cushing D) or non-pituitary disease incl idiopathic adrenal hyperplasia, adrenal adenoma, ectopic/paraneoplastic ACTH eg SCLC.

2. Conn S: excess aldosterone, usually from adrenal adenoma, → HTN and hypoK. Typically small and may be difficult to detect on CT.

3. Adrenal cortical carcinoma rare malignant disease. Arises from cortex and typically results in increased production in all of its hormones and precursors.

4. Pheochromocytoma. Arises from medulla, → incr cathecolamines. Episodic headaches, incr HR, diaphoresis, uncontrolled HTN.

Adrenal hypofunction

Substantial destruction of adrenal tissue is req. to produce adrenal insufficiency.

1. Addison d is usually not an imaging diagnosis. Can be caused by autoimmune destruction of adrenal glands or by prior infection.

2. Waterhouse-Friderichsen syndrome is a post-hemorrhagic adrenal failure seconday to N. meningitidis bacteremia.

3. Idiopathic adrenal hemorrhage usually unilateral, rarely causes hypofunction.