Adrenal Gland Anatomy, Hormones, and Disorders, Slides of General Surgery

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The Adrenal

Adrenal Anatomy

• Composed of a cortex and medulla, which have separate embryology.

Adrenal Anatomy

• The adrenal medulla is derived from cells of the neural crest that also form the sympathetic nervous system and the sympathetic ganglia.Some of these neural crest cells migrate into the adrenal cortex to form the adrenal medulla, but chromaffin tissue may also develop in extraadrenal sites.
• The most common site of extraadrenal chromaffin tissue is the organ of Zuckerkandl, located adjacent to the aorta near IMA.

Adrenal Anatomy

• The glands weigh about 4g each, located in the retroperitoneum along the superior- medial aspect of the kidneys.
• Yellow appearance because of their high lipid content.
• 3-5 cm in length, 4-6mm in thickness

Adrenal Anatomy

• The adrenal cortex is composed of three zones histologically.
• Outer zona glomerulosa , site for aldosterone synthesis.
• Central zona fasciculata and inner zona reticularis produce both cortisol and androgens.

Adrenal Anatomy

• Most of the blood supply to the medulla comes from venous blood draining through the cortex. This provides the adrenal chromaffin cells with high concentration of the enzyme phenyethanolamine N- methyltransferase (PNMT) required for conversion of norepinephrine to epinephrine.

The Cortex

• Zona glomerulosa is the exclusive site of production of aldosterone because it lacks the enzyme 17 alpha hydroxylase necessary for production of 17 a- progesterone and 17 a- pregnalone, which are the precursors to cortisol and androgens.

The Cortex

• Zona fasciculata and reticularis function as a unit to produce cortisol, androgens, and small amounts of estrogen, but it lacks the enzymes necessary to convert 18- hydroxycorticosterone to aldosterone.

Steroidogenesis

Cholesterol

Pregnenolone

Progesterone

11-Deoxycorticosterone

Corticosterone

Aldosterone

17-Hydroxypregnenolone

17-Hydroxyprogesterone

11-Deoxycortisol

Cortisol

DHEA

Androstenedione

Testosterone

Estradiol

3 β hydroxysteroid dehydrogenase

21β-hydroxylase

11 β-hydroxylase

Aldosterone synthase

Cholesterol desmolase 17 α-hydroxylase 17,20 lyase

Glucocorticoids

• Regulated by hypothalamus and pituitary via secretion of CRH and ACTH.

Glucocorticoids

• Normal daily production of cortisol is 10- 30mg.
• The liver is the main site of metabolism. Two major metabolites are 17- hydroxycorticosteroids and 17-ketosteroids, excreted in the urine.

Glucocorticoids

• Metabolic effects are stimulation of hepatic gluconeogenesis, inhibition of protein synthesis, increased protein catabolism, and lipolysis of adipose tissue.

Glucocorticoids

• Loss of collagen, impair wound healing by inhibition of fibroblasts.
• Inhibit bone formation, reduce calcium absorption by gut (steroid induced osteoporosis).

Glucocorticoids

• Numerous antiinflammatory actions, which include inhibition of leukocyte mobilization and function, decreased migration of inflammatory cells to sites of injury, decreased production of inflammatory mediators (IL-1, leukotrienes, and bradykinins).
• Also essential for cardiovascular stability, as evidenced by the collapse that occurs in patients with adrenal insufficiency.