Adrenal Cortex: Layers, Hormones & Disorders

The adrenal cortex, the largest and most visible part, is responsible for hormone production, which is vital for life. The cortex and medulla, part of the adrenal gland, produce separate hormones. 

• The adrenal cortex, the largest part of the adrenal gland, comprises three zones: zona glomerulosa, zona fasciculata, and zona reticularis
• Each produces specific hormones and serves as a secondary location for androgen production. 
• Adrenal glands, located above each kidney, regulate vital processes like the immune system, blood pressure, and stress response. 

Key terms: Adrenal gland, adrenal cortex, medulla, kidney, disorders, hormones, blood pressure, testosterone, cortisol. 

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Adrenal Cortex

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The biggest and most visible portion of the adrenal gland is the adrenal cortex. 

• It is linked to the creation of hormones, which are vital for life. 
• The adrenal medulla, situated in the adrenal cortex, produces stress hormones like adrenaline,
• It is enclosed in an adipose capsule, which forms a protective layer around the adrenal gland.

Adrenal Cortex

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Layers of Adrenal Cortex 

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The three primary zones or layers that make up the adrenal cortex are each controlled by a different hormone.

1. Zona glomerulosa: The zona glomerulosa is the main site for aldosterone production, regulated by the renin-angiotensin-aldosterone system.

• It affects kidney function, causing increased sodium reabsorption and excretion. 
• The cells are non-excitable, and they cannot synthesize cortisol or androgens.
• The expression of neuron-specific proteins in zona glomerulosa cells may reflect neuroendocrine differentiation.

2. Zona fasciculata: The zona fasciculata, located between the glomerulosa and reticularis, produces glucocorticoids, adrenal androgens, and estrogens.

• Its 3β-hydroxysteroid dehydrogenase activity increases its production, with ACTH stimulating cortisol secretion in humans. 
• Steroidogenic capacity increases during infant illness.

3. Zona reticularis: The zona reticularis, the innermost cortical layer

• It produces adrenal androgens, estrogens, and glucocorticoids due to its higher cofactors 
• Required for 17α-hydroxylase activity than zona fasciculata.

Read More: Nephron

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Hormones of Adrenal Cortex

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The many layers of the adrenal cortex create various hormones and serve various purposes. The adrenal cortex releases the following hormones:

1. Mineralocorticoids: Aldosterone, a mineralocorticoid, regulates blood pressure, increases sodium reabsorption and excretion, and is produced in the adrenocortical zona glomerulosa through aldosterone synthase.
2. Glucocorticoids: Glucocorticoids, primarily produced in the zona fasciculata, are regulated by the hormone ACTH from the anterior pituitary and are primarily released by the adrenal gland in humans and animals.
3. Androgens: Androgens, primarily produced in the zona reticularis, include - 

• Males' major sex hormone, testosterone, is in charge of forming secondary sex traits. 
• A strong form of testosterone that binds to androgen receptors is dihydrotestosterone. 
• For the production of testosterone and estrone, androstenedione is a less potent androgen precursor. 
• Dehydroepiandrosterone (DHEA) is an endogenous steroid that is widely distributed in the human circulatory system 
• It is used by both males and females to produce sex hormones.

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Disorders of the Adrenal Cortex

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There are several disorders that can impair adrenal gland function. Just above each kidney, tiny, triangular-shaped adrenal glands may be found. They are sometimes referred to as suprarenal glands. The overproduction or underproduction of certain hormones by the glands leads to adrenal diseases. 

• The adrenal glands generate the hormones aldosterone, adrenaline, and hydrocortisone, also known as cortisol.
• Addison's Disease: Addison's disease is a chronic condition where the adrenal glands fail to produce cortisol and aldosterone
• Essential hormones for stress response, blood pressure, heart function, immune system, and blood glucose levels.

• Cushing Syndrome: Cushing syndrome is a rare condition characterized by excessive cortisol levels, a stress hormone that regulates heart rate
• Congenital Adrenal Hyperplasia: Congenital adrenal hyperplasia (CAH) is a genetic disorder affecting the adrenal glands

1. Which produce essential hormones like cortisol, aldosterone, and androgen. 
2. CAH occurs when the adrenal glands lack a specific enzyme that produces these hormones, leading to insufficient production of cortisol

• Adrenal gland suppression: Adrenal gland suppression is a condition characterized by an imbalance in the production of cortisol or synthetic hormones like prednisone or dexamethasone.
• Hyperaldosteronism: Hyperaldosteronism is a condition where one or both adrenal glands produce too much aldosterone

1. A hormone that regulates blood pressure by controlling potassium and sodium levels.
2. There are two main types: primary hyperaldosteronism (Conn's syndrome) and secondary hyperaldosteronism
3. Both are caused by issues in the adrenal glands.

• Virilization: This condition occurs when the body produces excessive male sex hormones, primarily affecting females or boys before puberty.

Read More: Circulatory System

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What is Adrenal Insufficiency?

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Adrenal insufficiency occurs when the adrenal glands don't produce enough cortisol and aldosterone due to factors such as autoimmune diseases, tumours, tuberculosis, and infections. 

• Primary adrenal insufficiency occurs when the adrenal cortex is destroyed
• While secondary adrenal insufficiency is more common due to insufficient adrenocorticotropin (ACTH) production by the pituitary gland. 
• This can occur due to prolonged use of glucocorticoids, tumours in the pituitary glands, or surgery or radiation.

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Things to Remember 

• Adrenal glands regulate the immune system, blood pressure, and stress response, with cortex-producing hormones and medulla-producing hormones.
• The adrenal cortex, the largest part of the adrenal gland, is responsible for producing essential hormones
• While the adrenal medulla also contributes to these processes.
• The adrenal cortex produces various hormones, including mineralocorticoids, glucocorticoids, and androgens. 
• Mineralocorticoids regulate blood pressure and metabolism, while glucocorticoids stimulate fat breakdown and gluconeogenesis.
• Androgens, produced in zona reticularis, include testosterone, dihydrotestosterone, and dehydroepiandrosterone.
• Addison's Disease, Cushing's Syndrome, Congenital Adrenal Hyperplasia, Steroid Gland Suppression, Hyperaldosteronism, and Virginization are adrenal disorders.
• Adrenal insufficiency occurs when adrenal glands fail to produce cortisol and aldosterone due to autoimmune diseases.

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Previous Year Questions

1. Nascent hydrogen consists of..
2. In which of the following reactions the hydrogen peroxide acts as a reducing agent?..[JEE MAIN 2023]
3. Major product of the following reaction is..[JEE MAIN 2023]
4. The total current supplied to the circuit by the battery is...[AIEEE 2004]
5. The reading of voltmeter in the circuit shown is….[Rajasthan PMT 2023]
6. The oxidation of toluene to benzaldehyde by chromyl chloride is called...[NEET UG 1996]
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8. The order of stability of the following carbocations..[JEE MAIN 2013]
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10. Which one among the following metals is the weakest reducing agent?..[JEE MAIN 2023]