L17 - The Adrenal Gland Anatomy Flashcards
The zones of the adrenal gland can be remembered outside to inside by the mnemonic ‘salt, sugar sex’ what are the zones called and what is produced in each zone?
Outer - zona glomerulosa - mineralocorticoids (e.g. aldosterone)
Medial - zona fasiculata - glucocorticoids (e.g. cortis
Inner - zona reticularis - androgens
All are zones of the adrenal CORTEX, the adrenal medulla is neurocrime and where the chromatin cells are located which produce adrenaline and noradrenaline
All the hormones produced in the adrenal medulla are corticosteroids (steroid hormones), these are lipid soluble and this bind to intracellular receptors, what material are they all synthesised from?
Cholesterol - note also that androgens are produced in the gonads in adult males
What part of DNA do the steroid hormones specifically bind to to control transcription?
Hormone response elements
What does aldosterone play a central role in regulating and how?
Serum sodium and potassium and arterial blood pressure. It does this by upregulation of the Na/K pump
What is the best way to distinguish between a primary and secondary hyperaldosteronism?
Renin:aldosterone ratio - low = primary, high = secondary
What is the problem in a primary hyperaldosteronism, give an example of a cause
A defect in the adrenal cortex causing elevated aldosterone
Most common cause is bilateral idiopathic adrenal hyperplasia/aldosterone secreting adrenal adenoma (conn’s syndrome)/
What is the problem in secondary hyperaldosteronism, give an example of a cause
Renal artery stenosis (reduces blood flow to kidney so activates RAAS)/renin producing tumour
What are the signs of a hyperaldosteronism?
High blood pressure/LV hypertrophy/stroke/hypernatraemia/hypokalaemia (mainly the result of increased NA/k pump but some are from angiotensin II causing elevated blood pressure)
Cortisol accounts for 95% of glucocorticoid activity, it negatively feeds back on both CRH and ACTH release, what peripheral effects does it have on the body?
- increased proteolysis
- increased gluconeogenesis in liver
- redistribution of fat (to abdomen and face)
- anti-inflammatory effects (depression of immune response also)
- increased Na and water reabsorption through its effects of mineralocorticoid receptor
How can cortisol increase blood pressure?
Cortisol, although a glucocorticoid has a limited effect on the mineralocorticoid receptor too and can increase blood pressure in this manner
What is the most common cause of Cushing’s syndrome?
Prescribed glucocorticoids (steroids) - cause an excess of cortisol increasing the listed effects leading to cushinoid symptoms
Although steroids can cause Cushing’s syndrome, there are also endogenous causes, one is Cushing’s disease - what causes this and name another endogenous cause of Cushing’s syndrome
Cushing’s disease - ACTH secreting pituitary adenoma
Other endogenous causes - cortisol secreting adrenal tumour (adrenal cushings)/ nom pituitary-adrenal ACTH/cortisol secreting tumours normally small cell lung cancer
Prednisolone and dexamethasone are the two most commonly prescribed steroids, they are used to treat inflammatory disorders. Name some and explain why steroids should be tapered off rather than stopped abruptly
Asthma/Inflammstory bowel diseases/rheumatoid arthritis/auto-immune conditions
Needs to be tapered because steroids are effectively cortisol, stopping suddenly can cause cortisol withdrawal leading to muscle pain, hypotension (mineralocorticoid effect), vomiting and collapse
In addisons syndrome cortisol is not produced effectively due to a problem with the adrenal gland thus ACTH is still produced in high levels, how does this lead to hyperpigmentation?
Increased POMC (the prohormone to ACTH) stimulates MSH release leading to increased melanin and thus hyperpigmentation (dark pigment in skin)
What are the classical signs and symptoms of Addison’s disease (low cortisol, high ACTH)?
Postural hypotension (hypotension on standing)/lethargy/weight loss or anorexia/hyperpigmentation/hypoglycaemia
