MEH - Adrenal Glands Flashcards by T K

What are the three general areas of the kidney called?

Capsule, cortex, medulla (innermost)

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What are the three parts of the cortex called?

Zona glomerulosa, zona fasiculata, zona reticularis

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What is found in the medulla of the kidney?

Chromaffin cells, which secrete adrenaline and noradrenaline

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What does the zona glomerulosa secrete?

Mineralocorticoids, eg aldosterone

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What does the zona fasiculata secrete?

Glucocorticoids such as cortisol

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What does the zona reticularis secrete?

Androgens

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What are steroid hormones synthesised from?

Cholesterol, in the adrenal glands and gonads

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Steroid hormones are lipid soluble, true or false?

True

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How do steroids interact with cells?

They bind to nuclear receptors to modulate gene transcription

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How do corticosteroids exert their actions?

diffuse across plasma membrane
bind to glucocorticoid receptors which causes dissociation of chaperone proteins
receptor ligand complex translocates to nucleus and dimerises with other receptors
receptors bind to GREs or other transcription factors

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What class of steroid is aldosterone?

It is the most abundant mineralocorticoid

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Where is aldosterone made?

Synthesised and released by the zona glomerulosa of the adrenal cortex

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Which proteins are used to transport aldosterone?

Serum albumin and transcortin

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What is aldosterone’s main action?

Promotes expression of the Na+/K+ pump in the nephron, which influences water retention and blood volume and therefore blood pressure

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What triggers aldosterone release from the kidneys?

Angiotensin II

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What is hyperaldosteronism?

Too much aldosterone produced by the body

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What are the two categories of hyperaldosteronism?

Primary - defect in adrenal cortex

Secondary - overactivity of the RAAS

What are the signs of hyperaldosteronism?

high blood pressure
left ventricular hypertrophy
stroke
hypernatraemia
hypokalaemia

How is hyperaldosteronism treated?

Aldosterone-producing adenomas can be removed by surgery, or spironolactone can be given

How does spironolactone work?

It is a mineralocorticoid receptor antagonist

What class of steroid is cortisol?

Most abundant corticosteroid

Where is cortisol synthesised?

In the zona fasiculata, in response to ACTH

What is cortisol’s carrier protein in plasma?

Transcortin

What are the actions of cortisol?

increases protein breakdown in muscle, gluconeogenesis in the liver and lipolysis in fat
in charge of resistance to stress
anti-inflammatory effects (inhibits macrophages and mast cell degranulation)
depression of immune response

Describe the sequence of events from the hypothalamus to release of cortisol from the kidneys

- hypothalamus produces corticotropin releasing hormone (CRH) - anterior pituitary releases adrenocorticotropic hormone in response to this (ACTH) - adrenal cortex releases cortisol

What are the net effects of glucocorticoids on metabolism?

- increased glucose production - breakdown of protein - redistribution of fat

What is Cushing's Syndrome?

Chronic excessive exposure to cortisol

What are the signs and symptoms of Cushing's syndrome?

- moon shaped face - buffalo hump fat pad - abdominal obesity - purple striae - acute weight gain - hyperglycaemia - hypertension

What are the external causes of Cushing's syndrome?

Prescribed glucocorticoids (most common cause)

What is the difference between Cushing's disease and Cushing's syndrome?

Cushing's disease is due to a benign pituitary adenoma secreting ACTH, while Cushing's syndrome is an umbrella term for excessive cortisol exposure

What are steroid drugs used for?

Used to treat inflammatory disorders such as asthma, IBD, RA, etc.

What is Addison's disease?

Chronic adrenal insufficiency, usually caused by autoimmune response

What are the signs/symptoms of Addison's disease?

- postural hypotension - lethargy - weight loss - anorexia - increased skin pigmentation - hypoglycaemia

Why does hyperpigmentation occur in Addison's?

- decreased cortisol means that negative feedback on the anterior pituitary is reduced - this means that more POMC (building block) is required to form ACTH - POMC makes both ACTH and MSH (which forms melanin), so to maintain ACTH levels, more MSH is made as a byproduct

What is an Addisonian crisis?

Life threatening emergency due to adrenal insufficiency caused by severe stress, infection, trauma, cold, abrupt withdrawal of steroids, salt deprivation etc

What are the symptoms of an Addisonian crisis?

Nausea, vomiting, pyrexia, hypotension, vascular collapse

What is the treatment for an Addisonian crisis?

Fluid replacement and cortisol

What are the androgens that are released from the zona reticularis?

DHEA and androstenedione

What do 20% of chromaffin cells in the adrenal medulla lack?

N-methyl transferase, meaning they secrete noradrenaline instead of adrenaline

Which GCPRs can adrenaline act on?

B1 and B2, a1 and a2

What are the effects of adrenaline on the heart, lungs and blood vessels?

Heart - increase heart rate and contractility (B1) Lungs - bronchodilation (B2) Blood vessels - vasoconstriction in skin and gut (a1) or vasodilation (B2) in skeletal muscle

What is a pheochromocytoma?

Chromaffin cell tumour which secretes noradrenaline. It may cause life-threatening hypertension. Symptoms of anxiety, weight loss, headaches etc