Adrenal Cortex - Functions & Details

What is the Adrenal Cortex?

The adrenal glands are small organs that present at the top of each kidney. They play a crucial role in the body's response to stress and homeostasis. These glands are divided into two portions: the adrenal medulla and the adrenal cortex. The adrenal cortex is the outer region, comprising 80-90% of the gland. It secretes a variety of steroid hormones controlling metabolism, immune response, blood pressure, and many others related to the essential activities of living. Complete loss of adrenocortical hormones can lead to death due to dehydration and electrolyte imbalances in a few days to a week, unless hormone replacement therapy begins promptly.

Anatomy of The Adrenal Cortex

The paired adrenal glands, one which lies superior to each kidney, have a flattened pyramidal shape. In an adult, each adrenal gland is 3–5 cm in height, 2–3 cm in width, and less than 1 cm thick. The adrenal glands are anatomically located and structured for their essential functions:

• The position, sitting on top of each kidney, allows for the glands to secrete hormones directly into the bloodstream.

• Each adrenal gland has an outer cortex and an inner medulla.

• The cortex itself can be divided into three layers, each producing different hormones.

The adrenal cortex includes three distinct layers:

Zona glomerulosa

• The outermost layer of the adrenal cortex.

• Mainly responsible for the production of the mineralocorticoids, such as aldosterone.

• Maintains the balance between the levels of sodium and potassium, important in maintaining blood pressure and fluid balance.

Zona fasciculata

• The middle layer of the adrenal cortex.

• Producing glucocorticoids, primarily cortisol.

• Managing the responses to stress, metabolism, and immune system function.

Zona reticularis

• The innermost layer of the adrenal cortex.

• Producing androgens, including dehydroepiandrosterone (DHEA).

• Contributing to the development of secondary sexual characteristics and overall energy levels.

Functions of the Adrenal Cortex

Each layer of the adrenal cortex produces certain hormones crucial in different bodily functions:

Zona glomerulosa

• Hormone Produced: Mineralocorticoids (Aldosterone)

• It regulates homeostasis of two mineral ions, sodium ions (Na+) and potassium ions (K+)

• Helps to adjust blood pressure and blood volume.

• Promotes excretion of H+ in the urine, this removal of acids from the body can help prevent acidosis.

Zona fasciculata

• Hormone Produced: Glucocorticoids (Cortisol)

• Inside this layer, metabolism is regulated by the turning of lipids, proteins and carbohydrates into energy.

• Glucocorticoids are concerned with the regulation of the response to stressful and inflammatory stimuli.

• Inhibit white blood cells that participate in inflammatory responses and unfortunately, glucocorticoids also retard tissue repair, causing slow wound healing.

Zona reticularis

• Hormone Produced: Androgens (DHEA)

• In both males and females, the adrenal cortex secretes small amounts of weak androgens.

• After puberty in males, androgen is also released in much greater quantity by the testes. Thus, the amount of androgens secreted by the adrenal gland in males is usually so low that their effects are insignificant.

• In females, adrenal androgens play important roles. They promote libido and are converted into estrogens.

Hormonal Regulation & Feedback Mechanisms

The production and regulation of hormones produced by the adrenal cortex involve complex feedback mechanisms

Role of ACTH

• Produced by the pituitary gland.

• Stimulates the adrenal cortex to produce cortisol.

• ACTH levels are regulated by the hypothalamus through the release of corticotropin-releasing hormone.

Negative Feedback Mechanism

• High levels of cortisol first inhibit the release of CRH and later of ACTH, hence decreasing the production of cortisol.

• Maintains the balance of the hormones and prevents excess production of cortisol.

Disorders of The Adrenal Cortex

The disorders of the adrenal cortex result from an over or underproduction of hormones. This includes:

Hyperfunction

• Cushing's syndrome: This is caused by excessive production of cortisol and causes the patients to gain weight, hypertension, and skin changes.

• Hyperaldosteronism: Excessive production of aldosterone results in the patient complaining about high blood pressure and low potassium levels.

• Adrenogenital syndrome: This is caused by excessive androgen production.

Hypofunction

• Addison's disease: This occurs when there is insufficient production of cortisol and aldosterone.

• The symptoms include fatigue, weight loss, and reduced blood pressure.

Diagnostic Techniques

The following diagnostic tests are used to diagnose and monitor the condition of patients with disorders in the adrenal cortex:

Hormone Level Blood Tests

• Measure the levels of cortisol, aldosterone, and androgens to determine any imbalance.

• ACTH stimulation test, 24-hour urinary free cortisol test.

Imaging Studies

• CT (Computed Tomography) scans and MRI (Magnetic Resonance Imaging).

• Visualise the adrenal glands to identify any anatomical abnormalities like tumours.

Stimulation and Suppression Tests

• Stimulation Tests: Monitor the response of the adrenal gland to synthetic ACTH.

• Suppression Tests: Calculate the amount of cortisol produced by the adrenal gland by administering dexamethasone and then measuring the level of cortisol produced subsequently.

Mnemonics for Easy Revision

It takes effort to remember everything in a single go. We made the entire problem easy. Some of the tricks regarding Adrenal Cortex are given below which you can use to memorise the important points.

Hormones of the Adrenal Cortex

"AMC: Aldosterone, Mineralocorticoids, Cortisol"

• A: Aldosterone

• M: Mineralocorticoids

• C: Cortisol

Functions of Cortisol

"SMIB: Stress, Metabolism, Immune, Blood sugar"

• S: Stress response

• M: Metabolism regulation

• I: Immune suppression

• B: Blood sugar control

Aldosterone Regulation

"RAA: Renin-Angiotensin-Aldosterone"

• R: Renin

• A: Angiotensin

• A: Aldosterone

Disorders of the Adrenal Cortex

"ACC: Addison’s, Cushing’s, Conn’s"

• A: Addison’s disease

• C: Cushing’s syndrome

• C: Conn’s syndrome

Layers of the Adrenal Cortex

"GFR: Glomerulosa, Fasciculata, Reticularis"

• G: Zona Glomerulosa

• F: Zona fasciculata

• R: Zona Reticularis

Exam Relevance (NEET, CBSE, Paramedical)

During the preparation of the exam, there are different types of questions asked about Adrenal Cortex in different forms. The table given below contains the different patterns of questions asked in different exams.

Adrenal Cortex NEET MCQs

Q1. If 'X' is a hormone which controls the carbohydrate metabolism in the body and 'Y' is a hormone which controls the secretion of 'X', then 'X' and 'Y' are

1. Insulin and somatotropin

2. Aldosterone and growth hormone

3. Glucocorticoid and ACTH

4. Glucocorticoid and GHRH

Correct answer: 3) Glucocorticoid and ACTH

Explanation:

Role of Glucocorticoids:

They regulate glucose metabolism, but they also affect the metabolism of proteins and fats. Glucocorticoids include three primary hormones: cortisol (= hydrocortisone), corticosterone, and cortisoneGlucocorticoids stimulate gluconeogenesis, lipolysis, and proteolysis and inhibit cellular uptake and utilization of amino acids. Glucocorticoids, particularly cortisol, produce anti-inflammatory reactions and suppress the immune response

Hence, the correct answer is option (3) Glucocorticoid and ACTH.

Q2. Cortisol is secreted from

1. Pancreas

2. Thyroid

3. Adrenal

4. Thymus

Correct answer: 3) Adrenal

Explanation:

As we have learned

Adrenal Gland secretes Glucocorticoids. Glucocorticoids include three main hormones: cortisol (= hydrocortisone), corticosterone, and cortisone. Cortisol is the most abundant (about 95%). It stimulates the liver to synthesize carbohydrates from non-carbohydrates such as amino acids and glycerol.

Hence, the correct answer is option (3) Adrenal.

Q3. Glucocorticoids are produced by

1. Zona reticularis

2. Adrenal medulla

3. Zona fasciculata

4. Zona glomerulosa

Correct answer: 3) Zona fasciculata

Explanation:

As we have learned

The adrenal cortex secretes a group of hormones collectively known as corticoids. Among these, glucocorticoids play a crucial role in carbohydrate metabolism, helping to regulate glucose levels in the blood. These hormones, such as cortisol, also influence protein and fat metabolism and have anti-inflammatory effects, making them essential for maintaining homeostasis.

Hence, the correct answer is option (3) Zona fasciculata.

Also Read:

• MCQs on Adrenal Cortex

• Hormones of Heart, Kidney and Gastrointestinal Tract

• Thyroid Gland

FAQs on Adrenal Cortex

What is the adrenal cortex and where is it located?

The adrenal cortex is the outer layer of the adrenal gland, which is a pair of small glands situated on top of each kidney. It forms the major part of the adrenal gland and plays an essential role in survival. The adrenal cortex secretes hormones that regulate metabolism, immune system, blood pressure, and stress response. In absence of these hormones, many vital functions of the body cannot be maintained. Hence, the hormones secreted by adrenal cortex are considered important for survival.

What are the three layers of the adrenal cortex and their functions?

Each layer of the adrenal cortex has a distinct hormone and function, making it highly specialized. The three concentric layers are:

1. Zona glomerulosa – secretes mineralocorticoids (mainly aldosterone) that control sodium, potassium balance, and blood pressure.

2. Zona fasciculata – secretes glucocorticoids (mainly cortisol) that regulate stress response, metabolism of fats, proteins, and carbohydrates, and also suppress inflammation.

3. Zona reticularis – secretes androgens (like DHEA) that influence secondary sexual characteristics, muscle strength, and energy.

How is hormone secretion from the adrenal cortex regulated?

The adrenal cortex is under the control of the hypothalamus-pituitary-adrenal (HPA) axis. The hypothalamus secretes CRH (corticotropin-releasing hormone) which stimulates the pituitary gland to release ACTH (adrenocorticotropic hormone). ACTH then stimulates the adrenal cortex to produce cortisol. Cortisol itself acts by negative feedback on both hypothalamus and pituitary to prevent excess secretion. Thus, the system ensures balance and stability in hormone levels according to body needs.

What are common disorders of the adrenal cortex?

The disorders of the adrenal cortex result from hypersecretion and hyposecretion of the hormones. Some of the common disorders of the adrenal cortex include:

• Cushing’s syndrome: Excess cortisol → obesity, hypertension, and skin changes.

• Conn’s syndrome: Excess aldosterone → high blood pressure, low potassium levels, muscle weakness.

• Adrenogenital syndrome: Excess androgens → abnormal sexual development.

• Addison’s disease: Deficiency of cortisol and aldosterone → fatigue, weight loss, low blood pressure.