Flashcards in MEH - Adrenal Glands Deck (42):
What are the three general areas of the kidney called?
Capsule, cortex, medulla (innermost)
What are the three parts of the cortex called?
Zona glomerulosa, zona fasiculata, zona reticularis
What is found in the medulla of the kidney?
Chromaffin cells, which secrete adrenaline and noradrenaline
What does the zona glomerulosa secrete?
Mineralocorticoids, eg aldosterone
What does the zona fasiculata secrete?
Glucocorticoids such as cortisol
What does the zona reticularis secrete?
What are steroid hormones synthesised from?
Cholesterol, in the adrenal glands and gonads
Steroid hormones are lipid soluble, true or false?
How do steroids interact with cells?
They bind to nuclear receptors to modulate gene transcription
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
What class of steroid is aldosterone?
It is the most abundant mineralocorticoid
Where is aldosterone made?
Synthesised and released by the zona glomerulosa of the adrenal cortex
Which proteins are used to transport aldosterone?
Serum albumin and transcortin
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
What triggers aldosterone release from the kidneys?
What is hyperaldosteronism?
Too much aldosterone produced by the body
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
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?
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
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
- weight loss
- increased skin pigmentation
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