14. Hormones of adrenal cortex – glucocorticoids. Physiological effects and control of secretion. Pharmacological effects of glucocorticoids. Mineralocorticoids and adrenal sex hormones – physiological effects and control secretion.

Hormones of the Adrenal Cortex

The adrenal cortex is the outer region of the adrenal gland and consists of three histological zones, each responsible for producing a different group of steroid hormones:

1. Zona Glomerulosa – produces mineralocorticoids (mainly aldosterone).

2. Zona Fasciculata – produces glucocorticoids (mainly cortisol).

3. Zona Reticularis – produces adrenal sex hormones (mainly androgens like testosterone).

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Glucocorticoids

Physiological Effects

Control of Secretion

Physiological Effects

Cortisol, the main glucocorticoid, plays a critical role in metabolism and stress responses:

• Stimulates lipolysis: Breakdown of fat in adipose tissue, releasing fatty acids as an energy source.

• Stimulates gluconeogenesis: Promotes glucose production in the liver from non-carbohydrate sources.

• Increases protein catabolism: Enhances breakdown of proteins to release amino acids for gluconeogenesis.

• Enhances glucagon secretion: Supports further glucose release from the liver.

Control of Secretion

• Hypothalamus releases Corticotropin-Releasing Hormone (CRH) →

• Stimulates Anterior Pituitary to secrete Adrenocorticotropic Hormone (ACTH) →

• ACTH stimulates Zona Fasciculata to produce cortisol.

• Negative feedback: High cortisol levels inhibit CRH and ACTH secretion.

Pharmacological Effects of Glucocorticoids

Used clinically due to their powerful anti-inflammatory and immunosuppressive properties:

• Anti-inflammatory: Inhibits synthesis of inflammatory mediators (e.g., prostaglandins, cytokines).

• Immunosuppressive: Reduces lymphocyte and eosinophil counts, decreasing immune response.

• Used in treating autoimmune diseases, allergies, asthma, and organ transplantation.

Mineralocorticoids Physiological Effects

Control of Secretion

Physiological Effects

• Main mineralocorticoid: Aldosterone

• Regulates electrolyte and fluid balance by acting on the kidneys:

  • Increases sodium and water reabsorption

  • Enhances potassium excretion

  • Maintains blood pressure and blood volume

Control of Secretion

• Increased blood potassium (K⁺) stimulates aldosterone secretion.

• Renin-Angiotensin-Aldosterone System (RAAS):

  • Low blood volume/pressure → Renin release → Angiotensin II → Aldosterone secretion.

• Hyponatremia (low sodium) also stimulates aldosterone release.

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Adrenal Sex Hormones

Types and Effects

• Androgens (mainly from zona reticularis):

  • Testosterone: Male reproductive tissue development.

  • Androstenedione: Precursor to testosterone; contributes to early puberty changes like pubic and underarm hair.

  • Dihydrotestosterone (DHT): Crucial for male genital differentiation.

• Estrogens (in smaller amounts): Support female secondary sexual characteristics and menstrual cycle.

Control of Secretion

• Stimulated by ACTH from anterior pituitary (indirectly via CRH from hypothalamus).

• No strong negative feedback mechanism for adrenal androgens—secretion remains relatively constant.

Abnormalities of Adrenocortical Secretion

Abnormalities of Adrenocortical Secretion

1. Hypercortisolism (Cushing’s Syndrome)

   • Excess cortisol production

   • Symptoms: Muscle wasting, central obesity, hypertension, hyperglycemia, cardiac hypertrophy

2. Adrenal Insufficiency (Addison’s Disease)

   • Deficiency of cortisol (and often aldosterone)

   • Symptoms: Fatigue, hypotension, weight loss, hypoglycemia

3. Hyperaldosteronism (Conn’s Syndrome)

   • Excess aldosterone

   • Symptoms: Hypertension, hypokalemia, muscle weakness

4. Hypoaldosteronism

   • Low aldosterone production

   • Symptoms: Hypotension, hyponatremia, hyperkalemia