Describe different hormones of adrenal cortex and their physiological functions.

Adrenal Cortex: Structure and Zones

The adrenal cortex is divided into three distinct zones, each primarily responsible for synthesizing different corticosteroids:

• Zona Glomerulosa: Primarily produces mineralocorticoids (mainly aldosterone).
• Zona Fasciculata: Mainly produces glucocorticoids (mainly cortisol).
• Zona Reticularis: Primarily produces androgens (dehydroepiandrosterone – DHEA, and androstenedione).

Hormones of the Adrenal Cortex

1. Cortisol (Glucocorticoid)

Cortisol, often referred to as the “stress hormone,” is the principal glucocorticoid in humans.

• Synthesis & Regulation: Synthesized from cholesterol in the zona fasciculata. Its release is regulated by the hypothalamic-pituitary-adrenal (HPA) axis. CRH (corticotropin-releasing hormone) from the hypothalamus stimulates ACTH (adrenocorticotropic hormone) release from the pituitary gland, which in turn stimulates cortisol release. Cortisol exerts negative feedback on both CRH and ACTH.
• Physiological Functions:
  • Metabolic: Increases blood glucose levels (gluconeogenesis), promotes protein breakdown, and inhibits insulin sensitivity.
  • Anti-inflammatory: Suppresses the immune system and reduces inflammation.
  • Stress Response: Mobilizes energy stores to cope with stress.
  • Cardiovascular: Increases blood pressure.
• Clinical Significance: Cushing's syndrome (excess cortisol) and Addison's disease (cortisol deficiency) are major disorders.

2. Aldosterone (Mineralocorticoid)

Aldosterone is the primary mineralocorticoid responsible for regulating electrolyte and water balance.

• Synthesis & Regulation: Synthesized in the zona glomerulosa. Its release is primarily regulated by the renin-angiotensin-aldosterone system (RAAS). Decreased blood pressure or sodium levels trigger renin release, leading to angiotensin II formation, which stimulates aldosterone synthesis and release.
• Physiological Functions:
  • Sodium Reabsorption: Increases sodium reabsorption in the kidneys, leading to water retention.
  • Potassium Excretion: Promotes potassium excretion in the urine.
  • Blood Pressure Regulation: Increases blood volume and blood pressure.
• Clinical Significance: Hyperaldosteronism (excess aldosterone) can lead to hypertension and hypokalemia. Addison's disease also affects aldosterone production.

3. Androgens (Adrenal Androgens)

The adrenal cortex produces small amounts of androgens, primarily DHEA and androstenedione, in the zona reticularis.

• Synthesis & Regulation: Synthesis is stimulated by ACTH, but is less tightly regulated than cortisol.
• Physiological Functions:
  • Precursors: Serve as precursors for testosterone and estrogen.
  • Development: Contribute to pubic and axillary hair growth, especially in women.
  • Libido: Play a role in libido in both males and females.
• Clinical Significance: Congenital adrenal hyperplasia (CAH) can lead to excessive androgen production, particularly in females, causing virilization.

Hormone	Primary Zone of Synthesis	Main Function	Regulation
Cortisol	Zona Fasciculata	Metabolism, Inflammation, Stress Response	HPA axis (CRH, ACTH)
Aldosterone	Zona Glomerulosa	Electrolyte & Water Balance, Blood Pressure	RAAS (Renin-Angiotensin-Aldosterone System)
Androgens (DHEA, Androstenedione)	Zona Reticularis	Precursors to sex hormones, secondary sexual characteristics	ACTH

Recent Advances & Emerging Research

Research is increasingly focusing on the interplay between the adrenal cortex and the gut microbiome. Dysbiosis (imbalance in the gut microbiome) can influence adrenal hormone production and contribute to stress-related disorders. Furthermore, studies are exploring the role of epigenetic modifications in adrenal hormone regulation.

definition HPA Axis The Hypothalamic-Pituitary-Adrenal axis is a complex neuroendocrine system that controls the body's response to stress. It involves the hypothalamus, pituitary gland, and adrenal glands. statistic Individuals with Cushing's syndrome have a mortality rate 2-5 times higher than the general population, primarily due to cardiovascular complications. (Source: National Institute of Diabetes and Digestive and Kidney Diseases) NIDDK example CAH is a genetic disorder where the adrenal glands produce excess androgens, leading to premature puberty and virilization in females. It often requires lifelong hormone replacement therapy. faq What is the difference between cortisol and aldosterone? Cortisol is a glucocorticoid primarily involved in metabolism and inflammation, regulated by the HPA axis. Aldosterone is a mineralocorticoid primarily involved in electrolyte and water balance, regulated by the RAAS. scheme National Iodine Deficiency Control Programme While not directly related to adrenal hormones, this program highlights the importance of hormonal balance. Iodine deficiency impacts thyroid hormone production, demonstrating the interconnectedness of endocrine systems. 1993 case-study In the 1980s, Colombia attempted to reduce salt consumption through a heavy salt tax. This inadvertently led to a significant increase in hypertension, highlighting the importance of aldosterone and sodium regulation in public health. The tax was eventually repealed due to its unintended consequences. definition RAAS The Renin-Angiotensin-Aldosterone System is a hormonal pathway that regulates blood pressure and electrolyte balance. It involves the release of renin, angiotensin II, and ultimately aldosterone. statistic Approximately 1 in 2500 births are affected by congenital adrenal hyperplasia (CAH). (Source: NIH) NIH In conclusion, the adrenal cortex hormones—cortisol, aldosterone, and adrenal androgens—play pivotal roles in regulating numerous physiological functions, from metabolism and inflammation to electrolyte balance and sexual development. Understanding their synthesis, regulation, and clinical significance is crucial for maintaining overall health. Emerging research on the interplay between the adrenal cortex and the microbiome underscores the complexity of endocrine regulation and opens avenues for novel therapeutic interventions. Continued research into the intricacies of adrenal hormone function is essential for addressing endocrine disorders and improving public health.