18. Disorders of the Adrenal Cortex Flashcards
What are the three layers of the adrenal cortex?
Glomerulosa (salt), fasciculata (sugar), reticularis (sex hormones).
What levels do mineralocorticoids control?
Na and water in, K out.
How do steroid hormones work?
They act on the intracellular receptors and enter the nucleus to alter DNA transcription.
What happens in a deficiency of mineralocorticoid?
Low sodium, dehydration and high potassium.
What happens in an excess of mineralocorticoid?
High sodium, hypertension, low potassium.
What is the action of glucocorticoid?
Increased glucose production, breakdown of protein and redistribution of fat,
What can a deficiency of glucocorticoid cause?
Low glucose, weight loss, nausea and hypotension.
What can an excess of glucocorticoid cause?
High glucose, weight gain, increased appetite, hypertension and cushingoid.
What us congenital enzyme deficiency?
A rare paediatric condition which lowers Na and raises K levels. It’s a medical emergency.
What are the three steps in the hypothalamus-pituitary-adrenal axis?
Hypothalamus, pituitary and the end organ - adrenal.
What is the precursor to ACTH that’s secreted?
POMC.
How is POMC converted to ACTH?
POMC is cleaved into ACTH and MSH (melanocytes stimulating hormone).
What could cause a sudden, unexplained pigmentation?
Excess ACTH.
What can primary adrenal failure cause?
Addison’s disease.
What happens in primary adrenal failure?
There is high ACTH levels, but a lack of negative feedback. This means there are increased precursors to ACTH produced and MSH causes pigmentation.
How can an excess of ACTH affect the hypothalamo-pituitary-adrenal axis?
Causes more cortisol to be produced and released from the adrenal gland. This causes ACTH-dependent Cushing’s.
What causes ACTH independent Cushing’s?
A cortisol secreting adrenal tumour.
How can an adrenal tumour affect ACTH levels?
It lowers them.
What could the cause of corticosteroid excess be?
Cushing’s disease, ectopic ACTH, primary adrenal tumour or exogenous steroids.
When should cortisol levels be checked with suspected Addison’s disease?
In the morning where cortisol will be at its maximum.
When should cortisol levels be measured for suspected Cushing’s disease?
At midnight, where cortisol will be at its minimum.
What can the synacthen test be used for?
Primary adrenal failure, disease of the adrenal cortex, cortisol response to synthetic ACTH.
What is involved in the ACTH-stimulation test?
Inducing stress, namely hypoglycaemic stress caused in the insulin stress test.
How can corticosteroid deficiency be tested for?
Morning cortisol, stimulating HPA axis, synacthen test primary adrenal failure or insulin tolerance test pituitary ACTH deficiency.
