Transition block Flashcards
Causes of pseudohyponatraemia include..
Hyperlipidaemia (increase in serum volume) or a taking blood from a drip arm
Hyponatraemia may be caused by..
Water excess or sodium depletion
Lethargy, weakness, anorexia, nausea & vomiting, weight loss, ‘salt-craving’
Hyperpigmentation
Addison’s disease
Ix for addison’s disease
ACTH stimulation test (short Synacthen test)
Plasma cortisol is measured before and 30 minutes after giving Synacthen 250ug IM
In addison’s disease, if an ACTH stimulation test is not readily available (e.g. in primary care) then..
9am serum cortisol
<100 nmol/l
Hyperkalaemia
Hyponatraemia
Hypoglycaemia
Metabolic acidosis
Addison’s disease
Mx of addisonian crises
Hydrocortisone or IV normal saline infused over 30-60 mins or with dextrose if hypoglycaemic
Continue hydrocortisone 6 hourly until the patient is stable
Oral replacement may begin after 24 hours and be reduced to maintenance over 3-4 days
Mx of addison’s disease
Hydrocortisone - first half of the day
Fludrocortisone
Mx of intercurrent illness in addison’s disease
Glucocorticoid dose should be doubled, with the Fludrocortisone dose staying the same
ABG in Cushing’s disease
Hypokalaemic metabolic alkalosis
In cushing’s disease, ectopic ACTH secretion (e.g. secondary to ___________) is characteristically associated with very low potassium levels
Small cell lung cancer
Tests to confirm Cushing’s syndrome
Overnight (low-dose) dexamethasone suppression test
24 hr urinary free cortisol
Bedtime salivary cortisol
Cortisol not suppressed
ACTH suppressed
Cushing’s syndrome due to other causes (e.g. adrenal adenomas)
Cortisol suppressed
ACTH suppressed
Cushing’s disease (i.e. pituitary adenoma → ACTH secretion)
Cortisol not suppressed
ACTH not suppressed
Ectopic ACTH syndrome
An _________ test is used to differentiate between true Cushing’s and pseudo-Cushing’s.
Insulin stress
__________ sampling of ACTH may be needed to differentiate between pituitary and ectopic ACTH secretion
Petrosal sinus
Mx of Cushing’s disease
First-line = trans-sphenoidal removal of pituitary tumour (hypophysectomy)
Second-line = repeat trans-sphenoidal surgery, pituitary radiotherapy
Third-line = bilateral adrenalectomy
Source of prolactin
Anterior pituitary
Function of prolactin
Stimulates breast development (both initially and further hyperplasia during pregnancy)
Stimulates milk production
Prolactin secretion is under constant inhibition by…
Dopamine
What decreases prolactin secretion
Dopamine
Dopaminergic agonists
What increases prolactin secretion
Thyrotropin releasing hormone
Pregnancy
Oestrogen
Breastfeeding
Sleep
Stress
Drugs e.g. metoclopramide, antipsychotics
The syndrome of inappropriate ADH secretion (SIADH) is characterised by..
Hyponatraemia secondary to the dilutional effects of excessive water retention