Antidiuretic Hormone (ADH) is synthesized in the hypothalamus and secreted by the posterior pituitary. Its role plays part in the body’s osmotic balance, blood pressure regulation, and kidney function. ADH affects the ability of the kidney to reabsorb water and in addition induces expression of water transport proteins in the late distal tubule and collecting duct to increase water reabsorption (Cuzzo & Lappin, 2018). Diabetes Insipidus occurs with a decreased or absent ADH causing symptoms such as polyuria and polydipsia. Three types of diabetes insipidus include: neurogenic, nephrogenic, and polydipsic (McCance & Huether, 2014).
Neurogenic DI is the most commen and caused by insufficient amounts of ADH. Damage to the pituitary gland or hypothalamus from surgery, a tumor, a head injury or an illness can cause neurogenic diabetes insipidus by affecting the usual production, storage, and release of ADH (McCance & Huether, 2014).
Nephrogenic DI is often idiopathic. It occurs when there’s a defect in the kidney tubules. The defect may be due to an inherited disorder or a chronic kidney disorder (McCance & Huether, 2014).
Polydipsic DI can cause production of large amounts of diluted urine. The underlying cause is drinking an excessive amount of fluids that is caused by damage to the thirst-regulating mechanism in the hypothalamus. The condition has also been linked to mental illness (McCance & Huether, 2014).
“DI must be distinguished from other polyuric states, including diabetes mellitus. The basic criteria for the diagnosis of DI include polyuria, polydipsia, low urine specific gravity (<1.010), low urine osmolality (<200 mOsm/kg), hypernatremia, high serum osmolality (300 mOsm or more depending on adequate water intake), and continued diuresis despite a serum sodium level of 145 mEq/L or greater” (McCance & Huether, p. 720).
Treatment for neurogenic diabetes insipidus includes increasing water intake or desmopressin (DDAVP).This medication replaces the missing anti-diuretic hormone and decreases urination. Treatment for nephrogenic diabetes insipidus includes stopping initial cause if medication induced or treatment with thiazide diuretics. Treatment for polydipsic diabetes insipidus includes decreasing fluid intake (McCance & Huether, 2014).
A red flag symptom requiring urgent treatment of diabetes insipidus would include passing large amounts of dilute urine. This can cause severe electrolyte disturbances and intravascular depletion leading to shock (McCance & Huether, 2014).
Diabetes insipidus (DI) is a rare condition that occurs when your kidneys are not able to conserve water. DI is not related to diabetes mellitus, which is often referred to simply as diabetes. That means you can have DI without having diabetes. In fact, the condition can occur in anyone.
DI results in extreme thirst and frequent urination of dilute and odorless urine. There are several types of DI, and they can often be successfully treated (McCance & Huether, 2014). There are four types of diabetes insipidus including:
· Central or cranial diabetes insipidus, also called neurogenic diabetes insipidus
· Nephrogenic diabetes insipidus
· Dipsogenic diabetes insipidus due to malfunction of the thirst mechanism
Central or cranial diabetes insipidus
This occurs if there is a low level of vasopressin or antidiuretic hormone (ADH) in the body. The deficiency means the kidneys are not prevented from excreting large amounts of urine and instead large volumes of dilute urine are expelled, even when the body has become dehydrated. This also causes blood to lose water and become more concentrated and higher in salt. This results in dehydration and stimulation of the thirst center in the hypothalamus of the brain which causes a person to drink more.
This is the most common type of diabetes insipidus and it is mainly caused by disease, infection or injury to the pituitary gland or the hypothalamus gland.
The causes of cranial diabetes insipidus include:
· Genetic inheritance
The condition may be cause by an inherited mutation in the vasopressin gene, AVP-NPII which is transmitted to offspring in an autosomal fashion.
· Acquired disease may have the following causes:
· Tumors of the pituitary gland (pituitary adenoma), craniopharyngiomas and spread of cancer to the brain (in around 20% of cases). Granuloma formation in the pituitary gland may be another cause.
· Head injuries (in around 17%)
· Brain surgery (in around 9%)
· Meningitis and encephalitis may cause a small number of cases
· Sheehan’s syndrome and haemochromotosis or deposition of iron in pituitary/hypothalamic tissue
· Blood vessel complications such as those during pregnancy where the blood supply to the hypothalamus and the pituitary gland may be compromised
· Langerhans cell histiocytosis
· About a quarter of cases are idiopathic or without a known cause
Nephrogenic diabetes insipidus
This condition describes when the ADH level in the body is normal, but the kidneys do not respond adequately to the hormone. This may occur due to kidney damage or medications such as lithium reducing the expression of water channels in the kidneys called aquaporins.
Nephrogenic diabetes insipidus may be caused by:
· Genetic inheritance
Mutations in the genes that code for ADH receptors may be inherited and prevent these receptors from activating aquaporins in the kidneys. Inheritance is autosomal recessive in nature.
· Acquired disease may have the following causes:
· Metabolic disorders such as high blood sugar, high blood calcium and low potassium
· The use of medications such as demeclocycline or lithium which reduce aquaporin expression
· Obstructive uropathy
· Chronic kidney disease
· Polycystic kidney disease
Other types of diabetes insipidus
· Dipsogenic diabetes insipidus arises due to malfunction of the thirst mechanism. Damage to the hypothalamus or pituitary gland may lead to this condition.
· Gestational diabetes insipidus that occurs pregnancy because of the placenta producing vasopressinase – an enzyme that breaks down vasopressin (ADH). This leads to ADH deficiency. The symptoms usually resolve after childbirth.
Your doctor will take a sample of your urine to test for salt and other waste concentrations. If you have DI, your urinalysis will have a high concentration of water and a low concentration of other waste.
Water deprivation test
You will be asked to stop drinking water for a specified period before the test. You will then give blood and urine samples and your doctor will measure changes in:
· blood sodium and osmolality levels
· body weight
· urine output
· urine composition
· ADH blood levels
The test is done under close supervision, and may require hospitalization in certain people to ensure it’s done safely.
Magnetic resonance imaging (MRI)
This test uses a machine that will take an image of your brain tissue using magnets and radio waves. Your doctor will then look at these images to see if there’s any damage to the brain tissue that is causing your symptoms.
Your doctor will also look closely at images of your hypothalamus or pituitary gland for any damage or abnormalities.
This screening may be performed to look for an inherited form of DI based on your family history.
The hallmark symptom of diabetes insipidus is an increased need to urinate. This need can become exceptionally strong, making the need to use the bathroom immediate. When you do use the bathroom, you will pass large amounts of urine. The urine is usually highly diluted, resembling water. The appearance of clear urine is due to the high amount of water that it contains. As diabetes insipidus is a result of the malfunctioning of the body’s ability to regulate water levels, the water that it is supposed to hold onto is released in the urine.
Another hallmark symptom that is associated with diabetes insipidus is an excessive and intense thirst. The desire to drink can become so severe that it might seem unquenchable, despite how much water you consume.
Fatigue is a symptom that is commonly associated with several medication conditions. However, if you feel as if you have no energy and like all you want to do is sleep, no matter how much sleep you are getting, and you are also experiencing an increased need to pass urine and are excessively thirsty, then there is a very good chance that you have developed diabetes insipidus.
Just like the cells in your body rely on water to perform all its metabolic functions, your muscles rely on water to stay hydrated and healthy. If your water levels are not properly balanced, your muscles are not receiving the vital hydration that they need to stay healthy.
Diabetes insipidus can also cause patients to feel mentally confused and unable to concentrate. The reason that mental confusion can arise because of this condition is directly related to the lack of water in the body.