The most common signs and symptoms of diabetes insipidus include extreme thirst and excretion of large amounts of urine. The amount of urine excreted depends on the severity of the disease. Under normal conditions, a person produces less than 3 quarts (3 liters) of urine per day. However, in diabetes insipidus, the volume of urine produced per day can be as much as 16 quarts (15 liters).
Other signs and symptoms include needing to wake up at night to urinate (nocturia) and bed-wetting. Infants and children with diabetes insipidus may also experience insomnia, fever, vomiting, diarrhea, delayed growth and weight loss.
Another sign of diabetes insipidus in children is unexplained fussiness or inconsolable crying.
Diabetes insipidus is caused when the body can't regulate how it handles fluids.
Normally, the kidneys remove excess body fluids from the bloodstream. This fluid waste is temporarily stored in the bladder as urine, before urinating. When the fluid regulation system is working properly, the kidneys make less urine when the body water is decreased, such as through perspiration, to conserve fluid.
The volume and composition of the body fluids remain balanced through a combination of oral intake and excretion by the kidneys. The rate of fluid intake is largely governed by thirst, although habits can increase the intake far above the amount necessary.
The rate of fluid excreted by the kidneys is greatly influenced by the production of anti-diuretic hormone (ADH), also called vasopressin. The body makes ADH in the hypothalamus and stores the hormone in the pituitary gland, a small gland located in the base of the brain. ADH is released into the bloodstream when the body starts to become dehydrated. ADH then concentrates the urine by triggering the kidney tubules to release water back into the bloodstream rather than excreting as much water into the urine.
The way in which the system is disrupted determines which form of diabetes insipidus that a patient has:
Central diabetes insipidus
The cause of central diabetes insipidus in adults is usually damage to the pituitary gland or hypothalamus, most commonly due to surgery, a tumor, an illness (such as meningitis), inflammation or a head injury. For children, the cause is often an inherited genetic disorder. In some cases, the cause is unknown.
This damage disrupts the normal production, storage and release of ADH.
Nephrogenic diabetes insipidus
Nephrogenic diabetes insipidus occurs when there's a defect in the kidney tubules — the structures in the kidneys that cause water to be excreted or reabsorbed. This defect makes the kidneys unable to properly respond to ADH. The defect may be due to an inherited (genetic) disorder or a chronic kidney disorder.
Certain drugs, such as lithium and demeclocycline (a tetracycline antibiotic), also can cause nephrogenic diabetes insipidus.
Gestational diabetes insipidus
Gestational diabetes insipidus occurs only during pregnancy and when an enzyme made by the placenta — the system of blood vessels and other tissue that allows the exchange of nutrients and waste products between a mother and her baby — destroys ADH in the mother.
This condition — also known as dipsogenic diabetes insipidus or psychogenic polydipsia — can cause excretion of large volumes of dilute urine. Rather than a problem with ADH production or damage, the underlying cause is intake of excessive fluids. Prolonged excessive water intake by itself can damage the kidneys and suppress ADH, making the body unable to concentrate urine.
Primary polydipsia can be the result of abnormal thirst caused by damage to the thirst-regulating mechanism, situated in the hypothalamus. Primary polydipsia can also be caused by mental illness. In some cases of diabetes insipidus, doctors never determine a cause.
There are several risks and complications associated with diabetes insipidus.
Nephrogenic diabetes insipidus that is present at birth or develops after birth is inherited from parents. This type of diabetes insipidus affects male, although women can pass the gene to their children.
Complications of diabetes insipidus are connected to dehydration and electrolyte imbalance.
Complications associated with dehydration include:
- Dry mouth
- Changes in skin elasticity
- Low blood pressure (hypotension)
- Elevated blood sodium (hypernatremia)
- Rapid heartbeat
- Weight loss
Complications associated with electrolyte imbalance include: