Endocrinology Quiz: Adrenal Glands

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Questions and Answers

The adrenal gland is also called the ______ gland.

suprarenal

The outer region of the adrenal gland is called the adrenal ______.

cortex

Cushing's syndrome is a condition caused by prolonged exposure to ______.

cortisol

Cushing's disease refers to cases caused by a pituitary ______.

adenoma Signup and view all the answers

A diagnostic free cortisol level greater than 100 micrograms indicates ______'s syndrome.

Cushing Signup and view all the answers

Adrenal insufficiency, also known as ______'s disease, can lead to muscle weakness and fatigue.

Addison Signup and view all the answers

The adrenal medulla is located in the ______ of an adrenal gland.

center Signup and view all the answers

Symptoms of glucocorticoid excess may occur with administration of oral ______.

steroids Signup and view all the answers

The HPA axis is a major neuroendocrine system that controls reactions to ______.

stress Signup and view all the answers

Corticotropin releasing hormone (CRH) is released from the hypothalamic ______.

paraventricular nucleus Signup and view all the answers

ACTH stimulates the secretion of glucocorticoid steroid hormones and ______ from adrenal cortex cells.

androgen Signup and view all the answers

CRH binds to G protein-coupled ______ on the corticotropic cell membrane.

receptors Signup and view all the answers

Adrenocorticotropic hormone (ACTH) is transported by the blood to the adrenal ______.

cortex Signup and view all the answers

The ______ gland produces adrenaline and noradrenaline, which help control various bodily functions.

adrenal Signup and view all the answers

ACTH activates ______ cyclase to increase intracellular cAMP levels.

adenylyl Signup and view all the answers

Corticotropins are produced from the prohormone ______ in the anterior pituitary.

pro-opiomelanocortin Signup and view all the answers

Study Notes

Hypothalamus-Pituitary-Adrenal (HPA) Axis

The HPA axis is a major neuroendocrine system controlling reactions to stress.
Stress is any stimulus disrupting the body's internal balance (homeostasis).
The HPA stress response is driven primarily by corticotrophin-releasing hormone (CRH) released from the hypothalamic paraventricular nucleus (PVN).
The HPA axis mobilizes energy reserves ensuring the organism has resources to meet stress.

CRH

CRH is a 41-amino-acid peptide hormone.
CRH binds to G protein-coupled receptors on corticotropic cell membranes stimulating cAMP production.
The paraventricular nucleus of the hypothalamus synthesizes and secretes CRH.
CRH is transported to the anterior pituitary through the hypophyseal stalk's portal blood vessels.
CRH stimulates the secretion of stored ACTH from corticotrope cells.

ACTH

ACTH is a 39-amino-acid peptide hormone.
ACTH stimulates the secretion of glucocorticoid steroid hormones and androgens from adrenal cortex cells.
ACTH receptor (MC2 receptor) is a G protein-coupled receptor activating adenylyl cyclase increasing intracellular cAMP and activating protein kinase A.
ACTH stimulates cholesterol delivery by the steroidogenic acute regulatory (StAR) protein into mitochondria where the P450scc enzyme is located.
P450scc catalyzes the first step of steroidogenesis.
ACTH stimulates lipoprotein uptake into cortical cells increasing cholesterol bioavailability.
ACTH stimulates the transcription of steroidogenic enzymes, especially P450scc.

Adrenal Gland

The adrenal gland is a small gland located on top of each kidney (suprarenal gland).
It produces steroid hormones, adrenaline, and noradrenaline.
These hormones control heart rate, blood pressure, and other bodily functions.
The adrenal cortex is the outer, largest part of the gland, divided into three zones: zona glomerulosa (mineralocorticoids), zona fasciculata (glucocorticoids), zona reticularis (androgens).
The adrenal medulla is located in the center of the adrenal gland.
The adrenal gland is enveloped by a protective layer of adipose capsule.
Cholesterol is the starting material for steroid hormone biosynthesis.
Most cholesterol arrives at the adrenal cortex in the form of low-density lipoproteins.
Adrenal cortical cells take up cholesterol from blood via receptor-mediated endocytosis.

Pregnenolone

Pregnenolone is the common precursor for all steroid hormones produced by the adrenals and gonads.
Different enzymes are involved in the synthesis of steroid hormones from pregnenolone, involving different oxidation reactions.

Control of Adrenal hormones

ACTH is the only hormone known to control adrenal androgen synthesis, primarily in the zona reticularis.
Little or no androgen is produced in young children.
The reticularis develops before puberty.
Puberty is preceded by a dramatic increase in adrenal androgen production (principally DHEAS), responsible for pubic and axillary hair growth.
ACTH accelerates cholesterol delivery to the P450scc enzyme and forms pregnenolone.
With continued stimulation, ACTH stimulates transcription of P450 enzymes, LDL (low-density lipoprotein) receptors for cholesterol uptake, and the StAR protein.

Metabolic effects of Cortisol

Cortisol promotes gluconeogenesis and glycogen storage, affecting protein, fat, and carbohydrate metabolism.
Cortisol increases protein catabolism in muscle and decreases protein synthesis, providing amino acids for gluconeogenesis.
Cortisol increases lipolysis, providing glycerol for gluconeogenesis.
Cortisol decreases glucose utilization by tissues; decreases insulin sensitivity of adipose tissue, essential for survival during fasting through gluconeogenic routes.
Hypocortisolism (e.g., Addison's disease) results in hypoglycemia.
Hypercortisolism (e.g., Cushing's syndrome) results in hyperglycemia.

Anti-inflammatory and Immune Effects of Cortisol

Cortisol induces lipocortin synthesis, inhibiting phospholipase A2.
This inhibits prostaglandins and leukotriene synthesis, resulting in anti-inflammatory effects.
Cortisol inhibits interleukin-2 (IL-2) production and T lymphocyte proliferation.
Cortisol inhibits histamine and serotonin release from mast cells and platelets.
Cortisol can suppress the immune response and prevent organ transplant rejection when administered exogenously.

More actions of cortisol

Cortisol maintains normal blood pressure, up-regulating alpha-adrenergic receptors in arterioles.
Cortisol is needed for the vasoconstrictive response of arterioles to catecholamines.
Hypocortisolism results in hypotension.
Hypercortisolism results in hypertension.
Cortisol inhibits bone formation.
Cortisol decreases REM sleep, increases slow-wave sleep, and increases wake time.

Mineralocorticoid (Aldosterone)

Aldosterone promotes Na+ reabsorption and K+ secretion in the distal convoluted tubule, regulating total body Na+ by the kidney.
Na+ regulation controls plasma volume and arterial pressure.
In the absence of aldosterone, Na+ depletion rapidly lowers plasma volume and arterial pressure to fatal levels.
Added dietary salt can prevent this in acute cases.
Elevated plasma K+ can disrupt cardiac rhythm.
Long-term maintenance of mineralocorticoid levels requires administration of mineralocorticoids.

Control of Aldosterone Secretion

Aldosterone secretion is stimulated by decreased plasma Na+, increased plasma K+, and decreased arterial pressure.
ACTH has a minor effect on aldosterone secretion.

Renin-Angiotensin-Aldosterone System (RAAS)

RAAS is a complex pathway regulating blood pressure and fluid balance.
Renin, angiotensin I, angiotensin II, aldosterone, and ADH (antidiuretic hormone) are key components.

Aldosterone Receptor

Aldosterone binds to its receptor, triggering gene transcription and translation of aldosterone-induced protein (permease).
This permease increases cell permeability to Na+, leading to Na+ influx.
This increases Na+-K+-ATPase pump activity, contributing to Na+ and fluid retention.

HPA Feedback System

The HPA feedback system is regulated by plasma cortisol levels providing negative feedback on CRH and ACTH.

Cushing's Syndrome

Cushing's syndrome is a collection of signs and symptoms prolonged exposure to excess cortisol, regardless of etiology.
Signs/symptoms include high blood pressure; abdominal obesity with thin arms and legs; reddish stretch marks; round red face; fat between shoulders; weak muscles, bones, skin, which heals poorly.
Women may have more hair and irregular menstruation.
Mood, headaches, and chronic tiredness may occur.
Cushing's syndrome is due to excessive cortisol-like medication or tumors producing cortisol from the adrenal glands.
Pituitary adenomas causing Cushing's syndrome are called Cushing's disease.
A 24-hour free cortisol level exceeding 100 micrograms is diagnostic of Cushing's syndrome.

Exogenous Steroid Administration

Symptoms of glucocorticoid excess generally occur with oral steroid administration.
Steroid injections into joints and inhalers can cause Cushing's symptoms.

Zona Glomerulosa Disorders

Aldosteronism (adrenal tumor) results in hypersecretion of aldosterone, increasing Na+ and water reabsorption.
Symptoms include hypertension and edema. Loss of K+ disrupts neural and muscle function.

Adrenogenital Syndrome (AGS)

AGS results from adrenal androgen hypersecretion.
It often accompanies Cushing's syndrome, causing external genitalia enlargement in children and early puberty onset.
Masculinizing effects on women include a deeper voice and beard growth.

Adrenal Insufficiency (Addison's Disease)

Adrenal insufficiency occurs due to adrenal gland disorders (primary) or ACTH deficiency (secondary).
Symptoms include weight loss, muscle weakness, fatigue, low blood pressure, and occasional skin darkening.
About 70% of Addison's disease cases are due to autoimmune disorders causing adrenal cortex destruction.

Pheochromocytoma

Pheochromocytoma is a chromaffin cell tumor secreting catecholamines.
Symptoms include high blood pressure, heavy sweating, headache, rapid heartbeat (tachycardia), tremors, facial paleness, and shortness of breath (dyspnea).

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Description

Test your knowledge on the adrenal glands and their functions with this quiz. Explore concepts such as Cushing's syndrome, adrenal insufficiency, and the HPA axis. Perfect for students studying endocrinology or related medical fields.