Diabetes insipidus

Definition

It is a rare condition characterised by polydipsia (excessive thirst) and polyuria (excessive urination). Annoyingly called diabetes, and thus gets confused with diabetes mellitus.

Epidemiology

It's really very rare.

Pathophysiology

Two main causes:

• Central - The pituitary stops releasing antidiuretic hormone, causing diuresis (weeeeeeee). Can be seen with other deficiencies in hypopituitarism.
• Nephrogenic - The kidneys stop reacting to the antidiuretic hormone, also causing diuresis. Not as common as the other type.

Clinical Features

• Thirst
• Urinary frequency

In extreme cases, dehydration and shock will also present.

Investigations

1. Restrict fluids - this singles out people who just drink too much water.
2. Give them desmopressin - this singles out people with central diabetes insipidus, as the desmopressin simulates the ADH, and they should stop weeing.
3. If this fails - they have nephrogenic diabetes inspidus.

Management

If its central, give them desmopressin, or any ADH analogue.

If its nephrogenic,