The Adrenal Glands & Disorders Flashcards
Where are the adrenal glands located?
Pyramidal structure, on top of the kidneys
Describe the anatomical division of the adrenal gland in terms of the different layers of the cortex
Capsule: surrounds gland
Cortex: (GFR) zona glomerulosa (aldosterone) zona fasiculata (cortisol) zona reticularia (androgens) SALT, SUGAR, SEX
Medulla: chromaffin cells (NA, A)
Name the hormones produced by the different layers of the adrenal cortex
Glomerulosa: mineralocorticoids (aldosterone SALT)
Fasiculata: glucocorticoids (SUGAR)
Feticularis: androgens (SEX)
Describe in general terms the structure and functions of the steroid hormones
Synthesised from cholesterol in AG, lipid soluble (can diffuse PM), bind nuclear receptors to modulate gene transcription
What hormones do the class ‘steroid’ include?
Glucocorticoids (cortisol)
Mineralocorticoids (aldosterone)
Androgens
Oestrogen
Progestins
What are the 3 endogenous causes of cushings?
Pit
Ectopic
Tumour
What type of receptors do steroid hormones bind?
Nuclear
What is the role of 21-hydroxylase?
cytochrome P450 enzyme that is involved with the biosynthesis of the steroid hormones - in the adrenal cortex.
Def = low glucocorticoids/mineralocorticoids, high = androgens
Explain how the steroid hormones affect their target tissues
Nuclear receptor = modulate gene transcription. Diffuse PM, bind receptor, dissociation of chaperone protein, receptor ligand to nucleus, dimerisation, receptor binds GREs or transcription factors = reg gene transcription
Explain how cortisol secretion is controlled by ACTH and CRH
HPA axis: CRH by hypo to AP, ACTH by AP to AG, AG prod cortisol
-ve feedback of cortisol and ATCH
Explain how ACTH can lead to increased pigmentation in certain areas of the body
Adrenal insufficiency
Decreased cortisol
-ve feedback on AP reduced
More POMC required to synthesise ACTH
High ACTH = raised melanocyte stim hormone MSH = affects melanocytes
What are the signs of chronic high cortisol?
Re-distribution of fat (abdo, buffalo hump, moon face)
Acute weight gain
Purple striae
Hyperglycaemia
Hypertension
What are the causes of cushings syndrome?
External = prescribed glucocorticoids (MOST COMMON)
Endogenous = benign pit adenoma secreting ACTH, excess cortisol from adrenal tumour, not pit/adrenal tumours prod ACTH/CRH
What is cushings disease?
benign pit adenoma secreting ACTH
What are purple striae indicative of and why are they formed?
Cushings = proteolysis of skin
What is cushings SYNDROME?
Chronic excessive exposure to cortisol
What is the most abundant corticosteroid?
cortisol
Describe the main actions of cortisol.
Increased protein breakdown
Increase gluconeogenesis and glycogen storage
Increased lipolysis
Anti-inflam
Immune depression
What signals to the hypothalamus stim CRH release?
Pain, fever, hypoglycaemia, low BP
How does cortisol fluctuate?
Highest in morning/lowest at night
What is the function of aldosterone?
Reg gene transcription
Reg plasma Na, K+, arterial blood pressure
Promotes Na+/K+ pump expression = promotes reabsorption of Na and excretion of K+
Central role on RAAS
What is hyperaldosteronism?
High aldosterone
Primary = defect in adrenal cortex: bilateral idiopathic adrenal hyperplasia (high aldosterone:renin ratio)
Secondary = over activity of RAAS: tumour, renal artery stenosis (low aldosterone:renin ratio)
What are the signs of hyperalsosteronism?
High BP, hypernatriaemia, hypokalaemia
What protein transports cortisol and aldosterone?
transcortin
What is the treatment for hyperaldosteronism?
Spironolactone = mineralocorticoid receptor antagonist
What is Addisons disease?
Chronic adrenal insufficiency
Cause = autoimmune atrophy
Increased skin pigmentation
What is an addisonian crisis?
Symptom of severe adrenal insufficiency = hypotension, vascular collapse, pyrexia
Treat = fluids, cortisol
Describe in general terms the structure and functions of adrenaline
Made from tyrosine
Flight and flight = heart B1 increased HR/contractility, lungs B2 bronchodilation, blood vessels A1 con + B2 dil
Explain how adrenaline exerts its effects on target cells
GPCR: alpha 1 + 2, beta 1 + 2
Describe the components and overall function of the renin angiotensin aldosterone system
Slide picture
What are the inputs and outputs of RAAS?
In = hypotension, hypovolaemia.
Out = increased blood pressure, increased blood vol
Outline pheochromocytoma
Chromaffin cell tumour
Rare NA secreting tumour = severe hypertension
Describe tests of adrenal cortical function
CT, MRI, functional PET
Suspect Def = aldosterone def (low Na+, high K), ACTH def (low Na+, K+ norm, if no glucocorticoids taken = adrenal tumour, if taken = exogenous cushings), SynACTHen test (cort low)
Suspect Exc = aldosterone (low K+), cortisol (midnight, 24hr urine = high), dex supress: Low dose (low cortisol/ATCH), high dose (ACTH high in ectopic, low in pit adenoma)
Explain how cortisol can have weak mineralocorticoid and androgen effects
Aldosterone and cortisol (a glucosteroid) have similar affinity for the mineralocorticoid receptor; however, glucocorticoids circulate at roughly 100 times the level of mineralocorticoids. An enzyme exists in mineralocorticoid target tissues to prevent overstimulation by glucocorticoids.
