MLAB 2401: Clinical Chemistry Keri Brophy-Martinez Adrenal Gland: Overview

Introduction Adrenal Gland: An Overview Produces steroid hormones & neuropeptides essential for life Conditions affect blood pressure & electrolyte balance. Hypofunction is treated with exogenous hormone replacement, hyperfunction with pharmacologic suppression or surgery.

Adrenals Composed of outer adrenal cortex & inner adrenal medulla Pyramid-shaped, located just above & medial to kidneys Glands are about the size of a grape Arterial supply is symmetric; axons reach medulla through cortex.

Anatomy Zona Glomerulosa Zona Fasciculata Zona Reticularis G-Zone Cells outer 10% Synthesize mineralocorticoids Zona Fasciculata F-Zone Cells middle 75% Synthesize glucocorticoids Zona Reticularis R-Zone Cells inner 10% Secrete sex steroids (androgens)

Classes of Adrenal Cortex hormones Mineralocorticoids Regulate electrolytes Critical for sodium retention, potassium, & acid–base homeostasis Aldosterone Controlled by the renin-angiotension system Promotes potassium secretion Increases plasma sodium

Classes of Adrenal Cortex Hormones Glucocorticoids Involved with metabolism of protein, carbohydrate and mineral metabolism Critical to blood glucose homeostasis & blood pressure Plays a role in suppression of inflammatory and allergic reactions

Glucocorticoids Cortisol- principle member Functions Acts be penetrating cell nucleus, binding DNA, and altering the transcription of RNA Insulin antagonist 95% circulates bound to protein Breaks down muscle proteins with enzymes Mobilizes fat for energy purposes Lessens immune response by inhibiting antibody formation

Cortisol Regulation Hypothalamus secretes CRH (Corticotropin- releasing hormone) CRH activates adrenocorticotropic hormone (ACTH)in the anterior pituitary ACTH controls cortisol production Low levels of cortisol, promote ACTH release Elevated levels of cortisol, inhibit ACTH release

Cortisol/Cortisone Conjugated and excreted in the urine as 17- hydroxycorticosteroids (17-OHCS)

Classes of Adrenal Cortex Hormones Sex steroids Androgens Testosterone is the principal androgen Very little testosterone is secreted by the adrenal cortex

Adrenal Medulla Hormones Characteristics Produced in small amounts and extremely potent, rapidly inactivated Amine-type of hormone Produced from tyrosine, activate c-AMP Mobilize energy stores and prepares body for muscular activity Increased amounts secreted during stress

Catecholamine Members Norepinephrine/ Noradrenaline Epinephrine/Adrenaline Increases blood glucose via breakdown of glycogen Increases heart rate and blood pressure Causes sweating and dilation of the eyes

Excretion of Catecholamines Metabolism of catecholamines occurs by various pathways to form Vanillylmandelic acid (VMA) Metanephrine Normetanephrine Homovanillic acid