Endocrinology Flashcards
Hyponatremia
Hypo-osmolarity
Urine Na > 100
Euvolemic
SIADH
First exclude (Hypocortisolism, Hypothyroidism)
Causes
- small cell lung cancer, pancreas, prostate
- stroke, SAH, SDH, meningitis/encephalitis/abscess
- TB, pneumonia
- sulfonylureas, SSRIs, tricyclics, carbamazepine, vincristine, cyclophosphamide
- positive end-expiratory pressure (PEEP), porphyrias
Investigations
- Urine osmolality: Urine osmolality is inappropriately high (>100 mOsm/kg) in relation to serum osmolality, as the kidneys should normally dilute urine in the setting of low serum osmolality.
- Urine sodium concentration: Urine sodium concentration is typically high (>40 mmol/L) due to the action of ADH on the renal tubules.
Management
correction must be done slowly to avoid precipitating central pontine myelinolysis
- Ffluid restriction
- Demeclocycline: reduces the responsiveness of the collecting tubule cells to ADH
- ADH (vasopressin) receptor antagonists have been developed
DM has ECG changes and Hyperglycemia not controlled
To remember the causes of DKA, think 3 āIās which are insulin (missed), infection or infarction (i.e. MI)
Prolactinoma
Size (a microadenoma is <1cm and a macroadenoma is >1cm)
Prolactinomas are the most common type and they produce an excess of prolactin.
Management
Symptomatic: Dopamine agonists (e.g. cabergoline, bromocriptine) which inhibit the release of prolactin from the pituitary gland
Surgery in patients who cannot tolerate or fail to respond to medical therapy.
A trans-sphenoidal preferred unless there is a significant extra-pituitary extension
Amiodarone induced thyrotoxicosis:
How to differentiate between AIT1 and AIT2
Colour flow doppler ultrasonography needs to be performed by an experienced operator, but is thought to distinguish between the two causes of amiodarone induced thyrotoxicosis around 80% of the time.
In patients where the diagnosis is uncertain, radioiodine uptake, (which is low in type 2 disease) my further help differentiating between the two
