Physiological Effects of Adrenal Hormones and Catecholamines

Physiological Effects of Glucocorticoids

Glucocorticoids exert significant effects on various tissues and organs:

• Anti-inflammatory and immunosuppressive action: They inhibit inflammatory and allergic reactions at four levels: capillary, lymphatic cells, and organs.
• Action on the kidney and gastrointestinal tract: The elimination of corticosteroids restores glomerular plasma flow and favors the excretion of water and uric acid. High amounts of glucocorticoids can lead to gastric ulcers.
• Action on the cardiovascular system: Cortisol increases the effect of norepinephrine to stimulate smooth muscle and increases the strength of heart contractions.
• Action on growth: Cortisol demonstrates anti-growth effects by acting at digestive, bone, and muscle levels.

Sex Hormones and Mineralocorticoids

Sex Hormones: These have virilizing functions and are known as androgens. In women, 60% of testosterone is derived from adrenal androgens and the ovaries. While the physiological effects of adrenal cortical hormones are often negligible, they are significant in children and women.

Mineralocorticoids: These hormones alter the transport of Na, K, and Mg in the kidneys, sweat glands, and salivary glands. Aldosterone increases permeability and stimulates sodium reabsorption, which is coupled with the removal of potassium. This hormone also influences the acid-base balance.

Adrenal Medullary Hormones

The adrenal medulla synthesizes, stores, and releases catecholamines through two primary mechanisms:

• Internal control of synthesis: The synthesis of catecholamines is regulated by the enzyme tyrosine hydroxylase.
• External control of synthesis: The stimulus for secretion is the release of acetylcholine. The sympathetic-adrenal axis is activated during emergency situations.

Physiological Effects of Catecholamines

The effects of adrenal medulla stimulation and the sympathetic system are similar:

• Alpha receptors: Sensitive to adrenaline and noradrenaline; associated with excitatory body functions.
• Beta receptors: Sensitive to adrenaline and noradrenaline; associated with inhibitory body functions and myocardial excitation.
• Metabolic effects: Adrenaline stimulates hepatic gluconeogenesis and glycogenolysis. The overall effect of adrenaline on carbohydrate metabolism is to increase blood glucose concentration.