Diabetes insipidus

Question 1

What is diabetes insipidus (DI)?

Answer 1

Diabetes insipidus (DI) is a condition characterised by either a decreased secretion of antidiuretic hormone (ADH) from the pituitary (cranial DI) or an insensitivity to antidiuretic hormone (nephrogenic DI).

Question 2

What are the causes of cranial diabetes insipidus?

Answer 2

Causes of cranial DI include idiopathic, post head injury, pituitary surgery, craniopharyngiomas, infiltrative diseases like histiocytosis X and sarcoidosis, DIDMOAD syndrome, and haemochromatosis.

Question 3

What is DIDMOAD syndrome?

Answer 3

DIDMOAD is the association of cranial Diabetes Insipidus, Diabetes Mellitus, Optic Atrophy and Deafness (also known as Wolfram’s syndrome).

Question 4

What are the causes of nephrogenic diabetes insipidus?

Answer 4

Causes of nephrogenic DI include genetic factors affecting the vasopressin (ADH) receptor or aquaporin 2 channel, electrolyte imbalances like hypercalcaemia and hypokalaemia, lithium, demeclocycline, and tubulo-interstitial diseases.

Question 5

What are the features of diabetes insipidus?

Answer 5

The features of diabetes insipidus include polyuria and polydipsia.

Question 6

How is diabetes insipidus investigated?

Answer 6

Investigation involves high plasma osmolality, low urine osmolality, and a water deprivation test. A urine osmolality of >700 mOsm/kg excludes diabetes insipidus.

Question 7

What is the management for nephrogenic diabetes insipidus?

Answer 7

Management for nephrogenic diabetes insipidus includes thiazides and a low salt/protein diet.

Question 8

How is central diabetes insipidus treated?

Answer 8

Central diabetes insipidus can be treated with desmopressin.