Diabetes Insipidus (DI) is a disorder characterized by excretion of excessive dilute urine, followed by increased thirst. Diabetes insipidus should not be confused with diabetes mellitus because they are different terms with different underlying mechanisms and effects.
How is it caused?
Fluid regulation by kidneys seems to be a cumbersome mechanism. Diabetes insipidus happens when something gets wrong with this fluid regulatory and excretory mechanism. Antidiuretic hormone (ADH) is the key hormone involved in fluid regulation by kidneys. When body is in dehydrated state, the hypothalamus in brain senses it and starts excreting ADH. This ADH is then stored in pituitary gland temporarily and then released later into the bloodstream. The released ADH then reaches kidneys and enhances the water re-absorption by kidneys into the bloodstream. Thus, the whole purpose of ADH and kidneys is to conserve water in the body by producing concentrated urine. Anything that impedes the secretion or normal action of ADH will result in diabetes insipidus. Here are some types of diabetes insipidus:
- Central diabetes insipidus:
In this type of diabetes insipidus, there is decreased or deficient production of ADH. This happens in cases when hypothalamus or pituitary gland gets damaged. The causes of central diabetes include genetic disorders, trauma, inflammation or tumors of the glands.
- Nephrogenic diabetes insipidus:
In this type, the ADH production by hypothalamus is perfectly normal and the problem lies in the kidney. In nephrogenic diabetes insipidus, the kidney stops responding to the ADH. This leads to excretion of large amount of diluted urine.
- Gestational diabetes insipidus:
Gestation DI occurs during pregnancy when certain enzymes secreted by placenta start destroying the ADH
- Dipsogenic diabetes insipidus:
Also known by the name primary polydipsia or psychogenic polydipsia, this type of DI develops when thirst regulating mechanism of hypothalamus becomes defected. This is followed by increased thirst, excessive fluid intake and excretion of large amount of dilute urine.
Symptoms of Diabetes Insipidus
The typical signs and symptoms of diabetes insipidus are:
- Excessive urination with the need to urinate throughout the day and night.
- Intense or extreme thirst and craving for ice water.
- Children with diabetes insipidus may present with fever, vomiting, diarrhea, delayed growth, irritability, weakness and lethargy.
How is it diagnosed?
Diagnosis of diabetes insipidus cannot be made just on the basis of signs and symptoms because there are many other conditions that can present with similar symptoms. Therefore, in order to establish the diagnosis of diabetes insipidus, following tests are performed:
- Fluid deprivation test in which patient is asked to stop fluid intake and then changes in his urine output and urine concentration are measured.
- MRI of head
- ADH level
- Blood sodium
How can it be treated?
Treatment of diabetes insipidus depends on the underlying cause. Here are some treatment options for diabetes insipidus:
- Central DI is treated by replacing the deficient ADH with desmopressin intake.
- Nephrogenic DI is difficult to treat. If the drug such as lithium is causing it then intake of such toxic drugs should be stopped immediately. Nephrogenic DI is also treated by using anti inflammatory drugs and oral diuretics.
- Gestational DI is treated with the use of synthetic desmopressin.
- For primary polydipsia, the treatment approach is to reduce fluid intake and solving the underlying mental illness.