What is Diabetes Insipidus?
Normally, the kidneys secrete excess of water during urine formation, most of which is then reabsorbed. Antidiuretic hormone regulates the kidneys to reabsorb the water into the body; thus, the body releases concentrated urine. However, in the absence of ADH, the kidneys are unable to reabsorb the water and dilute urine is excreted in large quantities.
There are 2 forms of diabetes insipidus. Central diabetes insipidus is a condition that develops in the presence of insufficient quantities of ADH. Nephrogenic diabetes insipidus results when the ducts in the kidney are unable to reabsorb water in the presence of ADH.
Causes of Diabetes InsipidusCentral diabetes insipidus is caused mainly due to decrease in production of the ADH hormone. Some of the causes of central diabetes mellitus are:
- Head injury
- Infections (e.g., meningitis, encephalitis)
- Stroke affecting blood supply to the hypothalamus or the pituitary gland
- Inflammatory conditions affecting the brain which include sarcoidosis, systemic lupus erythematosus and so on
Causes of acquired nephrogenic diabetes insipidus are as follows:
- Kidney disorders, such as polycystic kidney disease
- Use of drugs (e.g., lithium, ofloxacin, demeclocyline, aminoglycosides etc.)
- Severe hypercalcemia (excess quantities of calcium) or hypokalemia (low levels of potassium)
- Formation of inflammatory granulomas in the kidney e.g. sarcoidosis
Symptoms of Diabetes InsipidusThe main symptoms of diabetes insipidus are as follows:
- Increased thirst and craving for iced water (polydipsia) – An individual can drink between 2 to 20 L of water a day
- Increased frequency of urination (polyuria), with production of large volumes of urine
- Symptoms due to dehydration and loss of electrolytes like dry mouth, low blood pressure, fatigue and muscle pains–Seizure – observed in infants and the elderly
- Changes in mental state - observed in infants and the elderly
- Lethargy – observed in infants and the elderly
Diagnosis of Diabetes InsipidusDiabetes insipidus may be diagnosed in the following ways:
- Analyzing the concentration of the urine, urine output
- Testing the blood for Osmolality of the plasma, electrolyte concentration, levels of blood glucose, levels of plasma AVP
- Scanning the brain using MRI
- Restricting the intake of water – This is a defining test to indicate the cause of excess urination.
- Genetic screening
Treatment for Diabetes InsipidusTreatment for diabetes insipidus differs based on the severity of the condition. Consuming adequate quantities of water may treat mild diabetes insipidus. The drugs used to treat central diabetes insipidus, include carbamezapine, desmopressin, indapamide, chlorpropamide, among others. These drugs improve the water retention capability of the kidneys. Children are favorably treated with vasopressin or desmopressin (the synthetic analogue of vasopressin).
Maintaining the sodium levels in the body, and thus, the water content in the body, are ways to treat nephrogenic diabetes. Nonsteroidal anti-inflammatory drugs are also used for the treatment.
Indomethacin and chlorothiazide are also used to treat children with nephrogenic diabetes insipidus.
Other therapeutic strategies to treat patients with nephrogenic diabetes insipidus are also being investigated. These include the use of phosphodiesterase (PDE) inhibitors, statins, heat shock proteins (HSP90) and prostaglandins.
Regular monitoring of the patient during treatment should be carried out by which one can identify water intoxication and electrolyte imbalance.