Week 3- The Adrenal Gland Flashcards
Where are the adrenal glands found?
Just above the kidneys
How many adrenal arteries are there?
Lots (57)
How many adrenal veins are there?
1
Where do left adrenal veins drain?
Rénal vein
Where do right adrenal veins drain?
Inferior vena cava
What makes up the adrenal cortex?
Zona glomerulosa (outermost layer), fasciculata (middle layer) and reticularis (inner layer)
What does the adrenal cortex do?
Secretes corticosteroids
What does the adrenal medulla do?
Secretes catecholamines eg adrenaline/noradrenaline
What does the zona glomerulosa synthesize?
Aldosterone
What do the zona fasciculata and reticularis synthesize together?
Cortisol (androgens & œstogen)
What molecule do steroids come from?
Cholesterol
What are the 3 classes of corticosteroids?
Mineralocortocoids (aldosterone ) Glucocorticoids (cortisol) Sex steroids (androgens, œstrogens)
What is the essential characteristic a steroid must have?
It must come from cholesterol
Describe how aldosterone is synthesized
The side chain of cholesterol is cleaved creating pregnenolone
Pregnenolone is oxidized to progesterone via 3 beta hydroxylation steroid dehydrogenase
An OH group is added at position 21 (11 deoxy corticosterone)
An OH group is added at position 11 (corticosterone)
An OH group is added at position 18 (aldosterone)
How is aldosterone output controlled?
By regulating the enzymes that hydroxylate progesterone to produce aldosterone
What is the enzyme that converts pregnenolone to progesterone?
3 beta hydroxy steroid dehydrogenase
What is a main role of aldosterone?
Control of blood pressure
What stimulates production of renin?
A drop in blood pressure
What is the effect of angiotensin II on the adrenals?
Causes activation of 3 hydroxysteroid dehydrogenase, 21/11/18 hydroxylase and side chain cleavage enzymes so aldosterone is produced
What are the 4 main physiological effects of cortisol?
Normal stress response
Metabolic effects
Weak mineralocorticoid effects
Renal and cardiovascular effects
What hormone controls cortisol secretion and where is it produced?
ACTH, produced in pituitary gland in brain
What is the effect of ACTH on the adrenals?
Activation of 3 hydroxysteroid dehydrogenase, 21/11/18 hydroxylase and side chain cleavage enzyme
What type of rhythm does cortisol have?
Diurnal/circadian
What is Addison’s disease
Primary adrenocortical failure- Autoimmune condition where the immune system destroys the adrenal cortex.
What happens hormone wise in Adddisons disease?
Pituitary starts secreting lots of ACTH and therefore MSH
What are symptoms of Addison’s disease?
Hyperpigmentation of skin, vitiligo, low BP, weakness, weight loss, nausea, diarrhea, vomiting
Why do patients with Addison’s disease have low blood pressure?
They have no cortisol or aldosterone
How can Addision’s disease result in death?
Lack of cortisol and aldosterone causes loss of salt, reducing BP eventually causing death
What is Cushing’s syndrome?
Too much cortisol or other glucocorticoid
What are visible symptoms of Cushing’s syndrome?
Fat pads, stretch marks, moon face, poor wound healing, easy bruising, thin skin, diabetes, hypertension
What are the 4 main causes of Cushing’s syndrome?
Taking steroids by mouth
Pituitary dependant
Ectopic ACTH
Adrenal adenoma/carcinoma
What does the adrenal medulla secrete?
Catecholamines (adrenaline/epiphrine [80%] and noradrenaline/norepiphrine [20%] )
What is the adrenal medulla derived from?
The ectodermal neural crest
What is the precursor for adrenaline and noradrenaline synthesis?
Tyrosine
Where are catecholamines stored?
Cytoplasmic granules
When are chatecholamines released and from where?
Released in response to Ach from preganglionic sympathetic neurones
How do Adr and NA circulate?
Bound to albumin
What is the role of catecholamines? What physiological responses occur to achieve this role
Fight or flight response
Tachycardia, sweating, higher blood glucose, alertness, vasoconstriction
What type of enzymes degrade catecholamines?
Hepatic
What are the names of the 2 enzymes that degrade catecholamines?
Monoamine oxidase
Catechol-O-methyl transferase
How is the balance of sodium and potassium ions affected in Addison’s disease?
More sodium ions are removed than ideal leading to low sodium
Less potassium is removed than ideal leading to high potassium
What is the medical name for low sodium?
Hyponatraemia
What is the medical name for high potassium?
Hyperkalaemia
What is the action of aldosterone on sodium and potassium levels in the blood and urine?
Removes sodium from urine into blood, moves potassium from blood to urine
The loss of cortisol In Addison’s disease causes the levels of which hormone to rise?
ACTH
How does excess ACTH lead to hyperpigmentation in Addison’s?
ACTH is made from a long peptide which is broken into many segments, one of these segments is the molecule MSH that stimulates melanin production so if more ACTH is made so is more melanin leading to hyperpigmentation
Describe how cortisol is synthesised from cholesterol
Cholesterol is converted to progesterone
Progesterone is converted to 17 OH prog by adding a hydroxyl group at position 17
17 OH prog is converted to 11 deoxycortisol
11 deoxycortisol is converted to cortisol
Describe how oestrogen is synthesised from cholesterol
Cholesterol is converted to progesterone
Progesterone is converted to 17 OH prog
17 OH prog is converted to sex steroids
Sex steroids are converted to androgens and then to oestrogen
