Arginine vasopressin deficiency
Arginine vasopressin deficiency is a disorder of water balance that causes the body to produce excessive amounts of urine, leading to severe thirst and a risk of dehydration.
Overview
Arginine vasopressin deficiency, previously known as neurohypophyseal diabetes insipidus, is a condition where the body cannot properly balance fluid intake and output. Because the body produces an excessive amount of urine (polyuria), individuals experience significant water loss, which leads to excessive thirst (polydipsia).
If individuals do not consume enough water, they can quickly become dehydrated, leading to dizziness and fatigue. Prolonged dehydration may result in confusion, low blood pressure, seizures, and coma. The condition often causes high levels of sodium in the blood (hypernatremia). Repeated cycles of dehydration can cause long-term health problems, particularly in children.
Causes & Risk Factors
The condition can be acquired or familial:
- Acquired form: Occurs when the brain is damaged by head injuries, brain tumors, brain surgery, certain diseases, infections, or bleeding in the brain. This form can occur at any time during life.
- Familial form: Caused by genetic variants in the AVP gene. Symptoms typically appear in childhood and worsen over time.
In 30 to 50 percent of cases, the cause is unknown, though some studies suggest a potential link to a malfunctioning immune system.
Mechanism
The AVP gene provides instructions for making the hormone arginine vasopressin (also called antidiuretic hormone or ADH). This hormone helps the kidneys manage the balance between fluid reabsorption and fluid release. When the body needs to conserve water, the brain releases AVP to signal the kidneys to reabsorb water and produce less urine. In arginine vasopressin deficiency, this process is disrupted, causing the body to make excessive amounts of urine.
Inheritance
Familial arginine vasopressin deficiency is almost always inherited in an autosomal dominant pattern, meaning one copy of the altered gene is sufficient to cause the disorder. In rare cases, it follows an autosomal recessive pattern, where both copies of the gene must have a variant.