How it works and what forms it comes in
Normally, the hypothalamus produces vasopressin, also known as antidiuretic hormone, and the pituitary gland releases it into the blood. The hormone causes the kidneys to return water back to the body, so the urine becomes concentrated. If there is not enough vasopressin or the kidneys do not hear it, water leaves in the urine almost unimpeded. There is a central form, when hormone production is affected, and a nephrogenic form, when the renal tubules are insensitive. Separately, we consider the transient variant of pregnancy and primary polydipsia, in which a person drinks an excess amount of liquid.
- Central form - vasopressin deficiency
- Nephrogenic - insensitivity of the kidneys to the hormone
- The form of pregnant women is temporary, disappears after childbirth
- Primary polydipsia - excessive drinking without illness
- Partial forms with moderate losses are possible
Causes and risk factors
The central form most often develops after neurosurgical operations, traumatic brain injuries, with tumors and cysts in the pituitary gland, inflammatory and autoimmune processes, less often it is hereditary or remains without an established cause. The nephrogenic form occurs with hereditary receptor defects, long-term use of lithium drugs, chronic kidney disease, a persistent increase in calcium or a decrease in potassium in the blood. In children, hereditary variants appear early, with poor weight gain, vomiting and fever without an obvious cause.
- Surgeries and injuries in the pituitary gland
- Tumors and cysts of the hypothalamic-pituitary region
- Autoimmune and inflammatory lesions
- Hereditary forms
- Long-term use of lithium drugs
- Chronic kidney disease
- High calcium and low blood potassium
- Pregnancy
Symptoms
Two key signs are a very large volume of urine and an unquenchable thirst. Urine is almost transparent, odorless, a person gets up several times at night, and during the day he does not part with a bottle of water and prefers cold water. Due to constant trips to the toilet, sleep is disturbed, fatigue, irritability, dry skin and mucous membranes appear. In young children the picture is different: anxiety, refusal to eat in favor of drinking, vomiting, constipation, poor weight gain, repeated rises in temperature. If access to water is limited, dangerous dehydration quickly develops.
- Excretion of more than 3 liters of light urine per day
- Constant strong thirst, craving for cold water
- Frequent night urination
- Dry skin and mucous membranes
- Weakness, headache, irritability
- In children - vomiting, constipation, poor weight gain
Diagnostics
First, they rule out the most common thing—diabetes mellitus: they measure blood glucose and look for sugar in the urine. Then the daily volume of urine and its specific gravity are assessed: in diabetes insipidus, the urine is persistently diluted. The key step is to simultaneously determine blood and urine osmolality and sodium levels, and if the picture is unclear, a fluid restriction test is performed under the supervision of a physician in a hospital, sometimes with the administration of a vasopressin analogue, to distinguish between the central and renal forms. If the central form is confirmed, an MRI of the pituitary gland must be done.
- Blood glucose, urine sugar test
- Daily volume and specific gravity of urine
- Sodium, potassium, calcium, blood creatinine
- Osmolality of blood and urine
- Dry eating test under medical supervision
- MRI of the pituitary gland with a central form
- Ultrasound of the kidneys if the renal form is suspected
Treatment
In the case of the central form, a synthetic analogue of vasopressin is prescribed in the form of tablets, sublingual forms or a spray - the dose is selected by the endocrinologist, focusing on the volume of urine, well-being and sodium level. Free access to water is always required. In the nephrogenic form, replacement therapy is ineffective: treat the cause, discontinue lithium preparations in consultation with the doctor, adjust calcium and potassium, use a diet with limited salt and protein and certain groups of diuretics, which paradoxically reduce the volume of urine. It is useful for the patient to carry information about the diagnosis with him.
- Analog of vasopressin in the central form
- Constant free access to water
- Treatment of a tumor or underlying disease
- Cancellation or replacement of lithium drugs according to the doctor’s decision
- Salt-restricted diet for kidney disease
- Monitoring blood sodium and urine volume
- Observation by an endocrinologist and repeat MRI if indicated
