Diabetes Insipidus

• ● Diabetes insipidus is characterized by decreased antidiuretic hormone (ADH) from posterior pituitary gland.

  ● ADH acts on kidney, it conserves water and decreases urine production.

  ● This causes less reabsorption of fluid in the kidney tubules, thereby increases urine output
• Possible Causes:

  1. Genetics, as an X-linked dominant trait or an autosomal recessive gene.

  2. Results from a lesion, tumor, or injury to the posterior pituitary gland which compresses the gland and affects ADH secretion

  3. Unknown cause.

  4. Kidney-related, although rare, is when pituitary function is adequate, but the kidneys’ nephrons do not respond to ADH
• ASSESSMENT

  Signs and symptoms of diabetes insipidus usually appear gradually

  1. Polyuria, with urine specific gravity as low as 1.001 to 1.005

  ● Parents will first notice bed wetting in an already toilet-trained child

  ● Urine may actually reach 4 to 10 liters in 24 hours, the normal is 1 to 2 liters only.

  ● This causes a very diluted urine; the specific gravity is low. The normal is 1.01 to 1.03.
• 2. Polydipsia or excessive thirst, relieved only by drinking water, not breast milk or formula

  ● Since water is mainly lost in the urine.

  3. Weight loss

  ● Because of a large loss of body fluid

  4. Dehydration

  ● Especially if diabetes insipidus is untreated, it can result to death.
• DIAGNOSIS

  ● Radiography, CT scan, or ultrasound of the skull to detect if tumor is present.

  ○ If present, this will warrant removal of tumor

  ● Administration of vasopressin (Pitressin) to rule out pituitary versus kidney disease. If urine output decreases, pituitary is at fault, but if kidney is the problem, urine will remain dilute and excessive.
• ○ Vasopressin is an endocrine drug which mimics the action of ADH, so if the cause is diabetes insipidus and it is pituitary in nature, the body will respond to this drug.

  ○ If urine output decreases therefore pituitary is at fault but if the kidney is the problem, urine will remain dilute and excessive.

  MANAGEMENT

  1. Surgery is the treatment of choice if a tumor is present.

  ● This will relieve pressure on the posterior pituitary gland and allow secretion of enough ADH
• 2. If from other causes, can be controlled by the administration of desmopressin (DDAVP), an arginine vasopressin.

  ● It can be given IV or oral or intranasal. It has a long duration of action about 15 to 21 hours.

  ● You might be wondering why vasopressin is not mentioned here, because vasopressin cannot be used as a dose or a maintenance for diabetes insipidus because it has a short duration of action only 2-8 hours.