Endocrinology Flashcards
what does the adrenal cortex produce, and what do they do?
steroids.
Salt - Sugar - Sex (it gets sweeter as you go deeper)
mineralocorticoids (e.g. aldosterone) - control sodium and potassium balance.
glucocorticoids (e.g. cortisol) - affect carbohydrate, lipid and protein metabolism.
androgens - sex hormones.
how is the adrenal cortex stimulated to produce cortisol/androgens?
corticotrophin-releasing factor (CRF) from hypothalamus stimulates ACTH secretion from pituitary - stimulates cortisol and androgen production.
what is the main cause of acromegaly?
pituitary adenoma - secretes excess GH
give 4 symptoms of acromegaly
persistent numbness and tingling in hands and feet
headache
amenorrhoea
sweating
arthralgia
increase in weight
low libido, backache
“my rings and shoes don’t fit anymore”
give 4 signs of acromegaly
growth of hands, feet and jaw
coarsening face, wide nose
macroglossia
darkened skin
obstructive sleep apnoea
goitre
carpal tunnel syndrome
puffy lips
laryngeal dyspnoea
what cardiac disease can acromegaly cause?
hypertrophic cardiomyopathy
what would you find on blood tests in acromegaly?
raised IGF-1, GH and prolactin - secreted by adenoma
what specific test would you do to confirm a diagnosis of acromegaly? what else can be helpful when trying to diagnose acromegaly?
oral glucose tolerance test - diagnostic if GH is not suppressed by the glucose.
old photos of the patient.
what is the 1st line treatment of acromegaly?
if that is CI, what would you try?
transphenoidal surgery.
if CI - somatostatin analogues (GH is inhibited by somatostatin) - lanreotide, ocreotide.
GH antagonist - pegvisomant.
what are the metabolic actions of GH?
stimulates IGF-1 to be produced and secreted by the liver.
increases collagen and protein synthesis, opposing the action of insulin (same as glucagon).
promotes retention of calcium and nitrogen.
mainly secreted nocturnally.
explain the renin-angiotensin-aldosterone system
renin is secreted by the kidneys in response to hypoperfusion of the kidneys, which then cleaves angiotensinogen into angiotensin I, which is an inactive form.
angiotensinogen is made in the liver, and circulates in the plasma.
angiotensin I is converted by ACE (produced in lungs) into angiotensin II in the lung and vascular endothelium.
angiotensin II causes vasoconstriction and stimulates the zona glomerulosa to increase its production of aldosterone - raises blood pressure and sodium retention - increasing blood volume.
what is diabetes insipidus?
passage of large volumes (>3L/day) of dilute urine due to impaired water resorption by kidney
what is the difference between cranial and nephrogenic DI?
cranial is due to reduced ADH secretion from posterior pituitary.
nephrogenic is due to impaired response of the kidney to ADH.
give 3 causes of cranial DI
idiopathic, congenital, tumour (craniopharyngioma, metastases, pituitary tumour), trauma, hypophysectomy, autoimmune hypophysitis, infiltration (histiocytosis, sarcoidosis), haemorrhage, infection (meningoencephalitis).
give 3 causes of nephrogenic DI
inherited.
metabolic - low potassium, high calcium.
drugs - lithium, demeclocycline.
chronic renal disease.
post-obstructive uropathy.
give 3 symptoms of diabetes insipidus
polyuria, nocturia, polydipsia, hypernatraemia
give 3 signs of diabetes insipidus
dehydration, enlarged and palpable bladder, no weight loss
what specific test can you do to confirm a diagnosis of diabetes insipidus, and what result would you expect?
fluid deprivation test - failure of urine concentration despite fluid restriction.
can give desmopressin - cranial DI will show an increase in urine osmolality.
how would you treat cranial diabetes insipidus?
desmopressin - synthetic ADH analogue.
MRI head to find cause.
why would treatment for cranial DI not work for nephrogenic and what would you use instead?
nephrogenic DI is a defect in channels rendering the kidneys insensitive to vasopressin - so desmopressin will have no effect.
treat cause.
if persists - bendroflumethiazide, and NSAIDs to lower the urine volume and plasma sodium.
explain the effect of vasopressin on the body
vasopressin is synthesised in the hypothalamus and migrates to the posterior pituitary where it is released into the circulation.
stimulates V2 receptors in kidney, making the collecting ducts more permeable to water via aquaporin 2 channels - decreasing diuresis and promoting water retention.
what types of malignancy can cause the syndrome of inappropriate ADH secretion?
small cell lung cancer, pancreas, prostate, thymus, lymphoma
list some causes of the syndrome of inappropriate ADH secretion
malignancies.
neuro - stroke, SAH, Guillain-Barre, SLE, vasculitis, meningoencephalitis.
resp - TB, pneumonia, abscess.
endocrine - hypothyroidism.
drugs - opiates, psychotropics, SSRIs, cytotoxics.
what is the main metabolic abnormality in the syndrome of inappropriate ADH secretion?
hyponatraemia
