Diabetes Insipidus, Causes and Types

What is diabetes insipidus?

Diabetes insipidus is a condition characterized by excessive thirst (polydipsia) and excessive urination (polyuria) either due to a dysfunction with arginine-vasopressin (AVP), which is also known as antidiuretic hormone (ADH), secretion or its action upon the kidneys. ADH is responsible for water reabsorption thereby concentrating urine and preventing the loss of large volumes of water in the urine. When ADH is lacking or ineffective, the kidneys allow large volumes of water to pass out in the urine.

In severe cases of diabetes insipidus, the water loss due to excessive urination can be as high as 20 liters of water in a day (24 hour period).

Different Types of Diabetes Insipidus

There are four types of diabetes insipidus :

1. Central – also referred to as cranial diabetes insipidus
2. Nephrogenic
3. Gestational
4. Dipsogenic

Causes of Diabetes Insipidus

Central

Decreased ADH levels or lack of ADH due to pathology within the hypothalamus (where ADH is manufactured) or pituitary gland (where ADH is stored and released). This is usually of a sudden onset.

Causes

• Inherited
  • Mutations of the vasopressin-neurophysin gene (dominant)
  • Wolfram syndrome – DIDMOAD = diabetes insipidus, diabetes mellitus, optic atrophy, deafness (recessive)
• Acquired
  • Trauma (head injury)
  • Infection- meningitis, encephalitis
  • Tumors
  • Post-operatively (pituitary surgery)
  • Idiopathic diabetes insipidus (autoimmune)
  • AV malformation
  • Aneurysm
  • Stroke
  • Hypoxic-ischemic encephalopathy – newborn hypoxia
  • Sheehan’s syndrome which is a pituitary infarct due to blood loss during childbirth (postpartum hemorrhage).

Nephrogenic

The kidneys are less responsive or resistant to the action of ADH and water reabsorption from the urine is impaired. This is usually of a gradual onset.

Causes

• Polycystic kidney disease
• Hypercalcemia which is elevated levels of calcium in the blood.
• Hypokalemia which is a low level of potassium in the blood.
• Kidney failure
• Genetic disorders
  • Cystinosis
  • V2 receptor mutation
  • Aquaporin-2 mutation
• Sickle cell disease
• Sjogren’s syndrome
• Drugs and heavy metal poisoning

Other Types of Diabetes Insipidus

• Gestational diabetes insipidus
  • Arises in pregnancy as enzymes produced by the placenta affect ADH.
• Dipsogenic diabetes insipidus
  • Defect in the thirst mechanism of the hypothalamus results in increased thirst and the greater fluid intake suppresses ADH secretion.