Diabetes insipidus (DI) is not diabetes mellitus. Diabetes insipidus is a condition in which the body cannot retain enough water, characterized by excessive thirst and urination. What causes diabetes insipidus is a deficiency or insensitivity to the hormone arginine vasopressin (AVP) also called antidiuretic hormone (ADH). A very rare condition, diabetes insipidus affects 1 in 25,000 people. There are four types of DI: central, a deficiency of ADH; nephrogenic, an insensitivity of the kidneys to ADH; gestational, a rare form in pregnant women; and dipsogenic, over intake of fluids. Symptoms include: extreme thirst, polyuria (excessive, diluted urine), nocturia (waking in the night to urinate), enuresis (bed-wetting), and feeling unwell due to tiredness.
What Causes Diabetes Insipidus – Kidneys and Hypothalamus
The kidneys are responsible for removing excessive fluids from the bloodstream, storing it in the bladder as urine. When certain circumstances, such as perspiration, remove fluids in a different way the kidneys respond by not producing more urine in order to conserve fluid. The volume of fluids in your body is regulated by fluid intake (thirst) while ADH influences excretion. ADH is produced in the hypothalamus and stored in the pituitary gland. It is released into the bloodstream, concentrating urine when it signals to the kidneys to reabsorb water back into the bloodstream.
To elaborate, central DI is caused by damage to the pituitary gland or hypothalamus, usually due to surgery, a tumor, illness, inflammation, or head injury, disrupting the production, storage, and release of ADH. Nephrogenic DI occurs when there is a damage or defect to the kidney tubules, the part of the kidney that can excrete and reabsorb water. When the tubules are dysfunctional they cannot respond to ADH. The causes for kidney defect can be genetic (it usually only affects males but can be passed from mother to child), caused by a drug interaction, or from chronic kidney disorder. Gestational DI is caused by an enzyme in the placenta destroys ADH in the mother. Dipsogenic DI (primary polydipsia or psychogenic polydipsia) is caused by an excessive consumption of fluids, damaging the body’s thirst-regulating mechanism in the hypothalamus. This form of diabetes insipidus is often caused by another disease or mental illness.
What Causes Diabetes Insipidus Symptoms
Dehydration is a considerable risk for people with diabetes insipidus. The symptoms of dehydration are muscle weakness, low blood pressure, elevated blood sodium, sunken eyes, fever, headache, rapid heart rate, and weight loss. Electrolyte imbalance is also a possibility as excessive urination removes minerals from the blood causing headache, fatigue, irritability, and muscle pain. A more serious consequence is water intoxication due to lowered sodium concentration in the blood, causing brain damage.
