The Adrenal Gland Flashcards
Where are the adrenal glands?
above the left and right kidneys
Label this diagram.
Where does the left adrenal vein drain into?
Renal vein
Where does the right adrenal vein drain into?
IVC (inferior vena cava)
Draw the gross anatomy of the adrenal glands/ kindeys?
describe the microanatomy of the adrenal glands.
Adrenal cortex
Adrenal medulla
What are the zones of the adrenal cortex?
Zona glomerulosa
Zona fasciculata
Zona reticularis
What does the adrenal cortex secrete?
corticosteroids e.g., cortisol
What does the adrenal medulla secrete?
Catecholamines
Adrenaline/epinephrine (80%)
Noradrenaline/norepinephrine (20%) [Dopamine]
What makes up the adrenal medulla?
Neuroendocrine
Chromaffin cells
What does epinephrine and norepinephrine derive from?
dopamine
What are the corticosteroids secreted from the adrenal cortex?
Mineralocorticoids (Aldosterone)
Glucocorticoids (Cortisol)
Sex steroids (Androgens, oestrogens)
What does each zone of the adrenal cortex secrete?
glomerulosa= aldosterone
fasciculate and reticularis= cortisol (androgens, oestrogens)
What is the microanatomy of the adrenal cortex?
Capsule
Zona glomerulosa
Zona fasciculata
Zona reticularis
Medulla
How do you stain the adrenal medulla?
Chromaffin stain
Label this diagram.
What does the outer zona glomerulosa make?
Aldosterone
What does the middle zona fasciculata make?
cortisol
Draw the adrenal microanatomy.
What does the zona reticularis secrete.
androgens (sex hormone)
- testosterone
What does the zona fasciculata secrete?
Glucocorticosteroids= e.g., cortisol
What is the adrenal gland secretion precursor?
Cholesterol
What is a steroid?
comes from cholesterol
numbers 1-27
what is an enzyme?
Protein that catalyses a specific reaction
Various enzymes are present in cells
Specific enzymes catalyse the synthesis of particular alterations to the molecule
How do you go from cholesterol to progesterone?
Cholesterol (side chain cleavage)-> pregnenolone (3 beta hydroxysteroid dehydrogenase)-> progesterone
What is the role of aldosterone?
Blood pressure control
How do you go from cholesterol to aldosterone?
Cholesterol (side chain cleavage)-> pregnenolone (3 beta hydroxysteroid dehydrogenase)-> progesterone
Progesterone (21 hydroxylase)-> 11 deoxycorticosterone (11 hydroxylase)-> corticosterone (18 hydroxylase)-> aldosterone
21-> 11 -> 18 hydroxylases
- oxidise 3 positions
How do you get from cholesterol to cortisol?
Cholesterol (side chain cleavage)-> pregnenolone (3 beta hydroxysteroid dehydrogenase)-> progesterone
Progesterone (17 hydroxylase)-> 17 hydroxy-progesterone (21 hydroxylase)-> 11 deoxy-cortisol (11 hydroxylase)-> cortisol
17-> 21-> 11 hydroxylase
What do sex steroids become?
androgens-> oestrogen and testosterone
What is the overall reaction of cholesterol forming different hormones?
What is the major net effect of aldosterone?
Major net effect is to conserve body sodium by stimulating its reabsorption
What is the mechanism of action of aldosterone?
Stimulates Na+ reabsorption in distal convoluted tubule and cortical collecting duct in kidney (and in sweat glands, gastric glands, colon)
Stimulates K+ and H+ secretion, also in distal convoluted tubule and cortical collecting duct
Increased sodium reabsorption water reabsorption, raising blood volume
When is renin released?
When blood pressure falls
What is decreased renal perfusion associated with?
with decreased arterial BP
What happens when there is decreased renal perfusion?
Increased renal sympathetic activity
- directed to juxtaglomerular apparatus cells (JGA)
Decreased Na+ load to top of loop of Henle (macula densa cells)
Is renin an enzyme or hormone?
Enzyme
What does renin stimulate?
- Liver secretes angiotensin (a protein)
- Renin cleaves angiotensin to make angiotensin I
- ACE (angiotensin converting enzyme) cleaves angiotensin I to angiotensin II
What does angiotensin II do?
Acts on zona glomerulosa of adrenal cortex increasing aldosterone secretion
Other effects e.g., vasoconstriction
What stimulates production of aldosterone?
low sodium
high potassium
What acts on the zona glomerulosa to increase aldosterone secretion?
ACTH
Increased K+
Decreased Na+
What is the effect of angiotensin II on the adrenals?
Activation of the following enzymes…
Side Chain Cleavage
3 Hydroxysteroid dehydrogenase
21 hydroxylase
11 hydroxylase
18 hydroxylase
What is the summary of aldosterone action?
Controls blood pressure, sodium increases and lowers potassium
How is cortisol secretion regulated?
ACTH
What are the physiological effects of cortisol?
Normal stress response
Metabolic effects
- peripheral protein catabolism
- hepatic gluconeogenesis
- increased blood glucose concentration
- fat metabolism (lipolysis in adipose tissue)
- enhanced effects of glucagon and catecholamines
Weak mineralocorticoid effects (aldosterone)
Renal and cardiovascular effects
- excretion of water load
- increased vascular permeability
Describe the feeedback of adenohypophysis.
CRH= corticotropin releasing hormone
negative feedback via circulation
What is MSH?
melanocyte stimulating hormone
- group of hormones in pituitary gland
- act on melanocytes in skin
Draw the HPA axis of adrenal gland.
What is the effect of ACTH on the adrenals?
Activation of the following enzymes…
Side Chain Cleavage
3 Hydroxysteroid dehydrogenase
21 hydroxylase
11 hydroxylase
17 hydroxylase
What kind of rhythm does cortisol have?
Diurnal rhythm
- a biological rhythm that is synchronized with the day/night cycle
When does cortisol rise?
just after ACTh rise
What is addison’s disease?
Primary adrenal failure
Autoimmune disease where the immune system decides to destroy the adrenal cortex (UK)
Tuberculosis of the adrenal glands (commonest cause worldwide)
Pituitary starts secreting lots of ACTH and hence MSH
What are symptoms of addison’s disease?
Hyperpigmentation of skin
Low blood pressure
Weakness
Weight loss
Vitiligo
Adrenal crisis
What are the symptoms of an adrenal crisis?
Why is there low blood pressure in addison’s disease?
No cortisol or aldosterone
Why do patients with Addison’s disease have a good tan?
POMC is a large precursor protein that is cleaved to form a number of smaller peptides, including ACTH, MSH and endorphins
Thus people who have pathologically high levels of ACTH may become tanned
POMC= pro-opio-melanocortin
What is a summary of addison’s disease?
Cortisol deficiency
Aldosterone deficiency
Salt loss
Low blood pressure
Eventual death
What would be the urgent treatment for an addisonian crisis?
Rehydrate with normal saline (due to low salt)
Give dextrose to prevent hypoglycaemia which could be due to the glucocorticoid deficiency
Give hydrocortisone or another glucocorticoid
What is cushing’s syndrome?
Too much cortisol
What happens if you have too much cortisol?
Metabolism changes and you put on weight
What can cause too much cortisol?
A tumour of the adrenal (excess cortisol)
A tumour of the pituitary (excess ACTH)
Why does increased cortisol SLOWLY cause a patient to be more and more unwell?
Cortisol is a clock control, with tumour/ it’s no longer cyclical and it doesn’t have a pulse
What are the symptoms of cushing’s syndrome? (7)
Thin skin
Proximal myopathy
Centripetal obesity (lemon on sticks)
Diabetes, hypertension and osteoporosis
Immunosuppression (reactivation of TB)
Moon face
Striae
Why does cushing’s syndrome occur?
Due to an excess of cortisol or other glucocorticoid
What are causes of cushing’s syndrome?
Taking steroids by mouth (common)
Pituitary dependent Cushing’s disease (pituitary adenoma)
Ectopic ACTH (lung cancer)
Adrenal adenoma or carcinoma
What are catecholamines?
Medulla derived from ectodermal neural crest
Precursor for Adr & NA synthesis = tyrosine
Catecholamines stored in cytoplasmic granules & released in response to ACh from preganglionic sympathetic neurones
How does dopamine turn to epinephrine and norepinephrine?
What are the roles of catecholamines?
‘Fight or flight response’ e.g. tachycardia, sweating, increased blood glucose, alertness, vasoconstriction
NA & Adr circulate bound to albumin
Degraded by two hepatic enzymes: monoamine oxidase & catechol-O-methyl transferase
