Endocrinology Flashcards
(40 cards)
What is primary adrenal insufficiency?
Adrenal glands are damaged
Reduction in secretion of cortisol and aldosterone
Commonest cause: autoimmune
Also called Addison’s
What is secondary adrenal insufficiency?
Inadequate ACTH
Low cortisol release
Loss or damage to pituitary
Fun fact: Sheehan’s syndrome is where massive blood loss during childbirth leads to pituitary gland necrosis
What is tertiary adrenal insufficiency?
Inadequate CRH release by the hypothalamus
Cause: long term oral steroids -> hypothalamus suppression. Long term steroids need to be tapered slowly for the adrenal axis to regain normal function
What are the symptoms of adrenal insufficiency?
Fatigue
Nausea
Cramps
Abdo pain
Reduced libido
What are the signs of adrenal insufficiency?
Bronze hyperpigmentation (ACTH stimulates melanocytes to produce melanin), particularly in skin creases
Hypotension (particularly postural hypotension)
What do investigations show in adrenal insufficiency?
Hyponatraemia
Hyperkalaemia
Early morning cortisol
Short synacthen test
ACTH
Adrenal cortex antibodies and 21-hydroxylase antibodies
Consider:
CT/MRI adrenals
MRI pituitary
What is the short synacthen test?
Give synacthen (synthetic ACTH)
Blood cortisol is measured at baseline, 30 and 60 minutes after administration. Cortisol should normally at least double - if not = primary adrenal insufficiency
What are the replacement steroids for adrenal insufficiency?
Hydrocortisone for cortisol
Fludocrotissone for aldosterone
What are the symptoms of an Addisonian crisis?
Reduced consciousness
Hypotension
Hypoglycaemia
Hyponatraemia
Hyperkalaemia
What is the management of an Addisonian Crisis?
IV hydrocortisone 100mg stat and then 100mg every 6 hrs.
IV fluid resus
Correct hypoglycaemia
Monitor electrolytes and fluid balance
Where in the adrenal cortex is aldosterone made?
Zona glomerulosa
What does aldosterone do?
Regulates BP
Regulates blood volume
Increases Na+ reabsorption by kidneys
What causes an increase in secretion of aldosterone?
Low BP
High levels of angiotensin II or K+ in the blood or ECF
What causes a decrease in the secretion of aldosterone?
High Na+ in blood or ECF
How does aldosterone work?
Increases no. of Na+/K+ pumps on the principle renal tubule cells and ENaC channels.
Increases the reabsorption of sodium and increases excretion of potassium
This increases the fluid volume and blood pressure in the capillaries.
Also increases H+ secretion
What are the symptoms of Conn’s syndrome (primary aldosteronism)
Benign tumour in the zona glomerulosa cells
Hypokalaemia
Mild metabolic alkalosis
Increase in blood volume -> increased BP
Decreased plasma renin levels
Muscle weakness due to low levels of ECF K+
What are the management options for hyperaldosteronism?
Tumour removal
Spironolactone: aldosterone antagonist
What does ADH do?
Stimulates water reabsorption from eh collecting ducts in the kidneys
What can cause SIADH?
Posterior pituitary secreting too much
Small cell lung cancer secreting ADH
Also:
Post-op
Infection such as atypical pneumonia and lung abscesses
Head injury
Medications: (thiazide diuretics, carbamazepine, vincristine, cyclophosphamide, antipsychotics, SSRIs, NSAIDs)
Malignancy
Meningitis
What does SIADH cause?
Dilution of sodium in the blood: euvoleumic hyponatraemia
More concentrated urine with him urine sodium
What are the symptoms of SIADH?
Non-specific
Headache
Fatigue
Muscle aches and cramps
Confusion
Severe hyponatraemia: seizures and reduced consciousness
How do you diagnose SIADH?
Exclusion of other causes of euvolaemic hyponatraemia (synacthen test, no diuretics, no D&V, no excessive water intake, no CKD or AKI)
How do you manage SIADH?
Establish and treat the cause
Why is important to correct sodium slowly?
To prevent central pontine myelinolysis (a change in sodium of less than 10 mmol/L per 24 hrs
You correct sodium by:
Fluid restriction
Tolvaptan (ADH receptor blockers) - but this can cause a rapid increase so only specialist use
