Antidiuretic Hormone Disorder

What is a common symptom of diabetes insipidus & diabetes mellitus?

Excess dilute urine → Extreme thirst

What are the 2 types of diabetes insipidus and the differences between the two?

Pituitary (Cranial): lack of vasopressin (ADH) production - most common. Nephrogenic (Partial): Kidneys don’t respond to ADH.

Drug treatment for pituitary (cranial) diabetes insipidus

Vasopressin or desmopressin

Drug treatment for nephrogenic (partial) diabetes insipidus

Thiazide diuretic (paradoxical effect)

Differences between desmopressin & vasopressin?

Desmopressin is more potent and has longer duration vs vasopressin. Desmopressin has no vasoconstrictor effect.

What electrolyte imbalance can desmopressin cause?

Hyponatraemia

Common side effect of desmopressin

Nausea

Electrolyte imbalance caused by inappropriate ADH secretion (i.e. too much ADH released)?

Hyponatraemia (body retains too much water → dilutes salt conc in blood)

Treatment pathway for inappropriate ADH secretion (i.e. too much ADH released)

Fluid restriction → demeclocycline (blocks renal tubular effect of ADH) → tolvaptan (vasopressin antagonist)

Why should you not rapidly correct hyponatremia with tolvaptan?

Causes osmotic demyelination → serious neurological events