INTRODUCTION

The adrenal glands are essential to normal physiologic functioning. Significant pathology requiring surgical intervention may result from hyperplasia, adenoma formation, or malignancy.

The right adrenal gland is pyramid-shaped (“witch’s hat”) and lies above the upper pole of the right kidney, between the liver and the diaphragm. The left adrenal gland is found between the kidney and aorta, near the tail of the pancreas and the splenic artery.

The adrenal gland is approximately one third the size of the kidney at birth. However, in the adult, the adrenal gland is only one thirtieth the size of the kidney. This change in proportional size is a reflection of renal growth as well as the involution of the fetal adrenal cortex after birth. A normal adrenal gland in an adult weighs approximately 4 to 6 grams.

FUNCTION

The adrenal glands are composed of two functionally distinct endocrine units, the adrenal cortex and medulla, contained within a single capsule. Each has distinct embryologic, anatomic, histologic, and functional characteristics.

Adrenal cortex function — The adrenal cortex is divided into three functional zones.

● The zona glomerulosa secretes mineralocorticoids (aldosterone) which regulate sodium and potassium homeostasis

● The zona fasciculata secretes glucocorticoids (most importantly, cortisol)

● The zona reticularis secretes sex steroids (primarily androgens)

Adrenal medulla function — The adrenal medulla synthesizes and secretes catecholamines, which modulate the body’s sympathetic response to stress. The synthesis of catecholamines from the amino acid tyrosine is localized in the cells of the adrenal medulla and the organ of Zuckerkandl, and is modulated by phenylethanolamine-N-methyltransferase (PNMT), an enzyme that converts L-noradrenaline to L-adrenaline. Because PNMT is limited exclusively to these cells, adrenaline-secreting tumors arise predominantly in the adrenal medulla and the organ of Zuckerkandl.