mix of endo Flashcards
(33 cards)
Diabetes insipidus is due to lack of ___
ADH
classification of Dibaetes insipidus
cranial or nephrogenic
2 symptoms of diabetes insipidus
polyuria & polydipsia
type of diabetes where the collecting ducts of the kidney do not respond to ADH
Nephrogenic diabetes insipidus
type of diabetes where the hypothalamus does not produce ADH
cranial diabetes insipidus
drug causing nephrogenic DI
lithium
electrolyte imbalance in diabetes insipidus
hypernatraemia
osmolality findings in diabetes insipidus
low urine osmolality
&
high serum osmolality
test for diagnosing diabetes insipidus?
Water deprivation test
/
desmopressin stimulation test
where is ADH released from
posterior pituitary gland
ectopic ADH secretion?
small cell lung ca
mechanism of ADH
acts on distal convoluted tubule & collecting duct to increase water reabsorption independant of sodium
ADH stimulates the insertion of aquaporin-2 channels onto the luminal membrane, allowing free entry of water
sodium level in SiADH
euvolemic hyponatraemia
due to dilution
urine osmolality is ___
low
what can severe hyponatraemia cause?
seizures & reduced consciousness
medications that can cause SiADH
- thiazide diuretics
- carbmazepine
- cyclophosphamide
- antipsychotivs
- SSRI
- NSAIDs
why is it important to correct sodium level slowly?
prevent; ‘Central pontine myelinolysis’
e.g. of ADH receptor blockers
Tolvaptan
1st phase of central pontine myelinolysis & why?
water moves from blood to cells in the brain across BBB. causing brain to swell
- encephalopathic
- confused
2nd phases of central pontine myelinolysis
demyelination of the neurones, particularly in the pons. May present as cog&behavioural changes, spastic quadriparesis, pseudobulbar palsy
what is ADH produced by?
magnocellular neurons in the paraventricular & supraoptic nuclei of the hypothalamus
what triggers release of ADH
rising plasma osmolality
urinary test results in SiADH
high urine osmolality
&
high urinary sodium
what produces calcitonin?
parafollicular C cells
