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Diabetes Insipidus: Definition, Causes & Types

Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

Although you have heard of diabetes, chances are you haven't heard of an unrelated disease called diabetes insipidus. This lesson will define this disease as well as list the different types, while trying to ascertain the cause of diabetes insipidus in a three-year old child.

Case Study, Definition and Symptoms

A three-year-old male won't stop drinking water and juice. He urinates more than he used to, his urine is diluted, and he becomes hysterical when fluids are withheld. What's going on here? There are several possibilities, and doctors would need to run tests to pinpoint the exact cause. However, these symptoms sound like the three-year old could have diabetes insipidus, which is a condition that causes excessive thirst and increased urination. Sometimes, you may hear doctors refer to diabetes insipidus as DI.

Urine can be dilute, or water-colored, or concentrated, or really yellow. The urine here slightly concentrated
ur

While part of its name is 'diabetes,' it isn't the type of diabetes you're probably thinking about. And while some of the symptoms are similar, its causes are quite different. So, when you hear 'diabetes insipidus,' realize we are not talking about the diabetes that requires sugar-levels and insulin to be monitored.

So, why do they have the same name? Well, an ancient Greek doctor used the term 'diabetes' to describe a condition where someone urinated a lot (which also occurs in the type of diabetes you've probably heard of). Diabetes means 'to pass through,' so urine passing through the body seemed to fit. And 'insipidus' means 'no taste' in Latin, which is fitting because there is no extra sugar in the urine when a patient has diabetes insipidus, unlike the more common types of diabetes.

Before we go into the specific types of diabetes insipidus, let's go over some more of the symptoms.

  • Excessive thirst
  • Excessive urination
  • Unexplained weight loss
  • Irritability (fussiness in children)
  • Fever
  • Diarrhea
  • Headaches
  • Increased heart rate
  • Too much sodium in the blood
  • Bed-wetting (children)
  • Delayed growth
  • Dehydration
  • Low blood pressure
  • Muscle cramps

Remember, the boy in our case study has excessive thirst, increased urination and is irritable.

Causes and Types

The excessive thirst and urination seen in the three-year old boy is due to his body's inability to handle fluids. The causes of diabetes insipidus are varied, so let's go through the different types so we can try to pinpoint the cause for the boy.

  • Central diabetes insipidus - Your kidneys regulate the fluid in your bloodstream with the direction of a hormone called the anti-diuretic hormone, or ADH for short. If you have extra fluid, it goes into the bladder and is removed from the body when you urinate. ADH is made in a part of your brain called the hypothalamus and is stored and released by the pituitary gland. When you don't have enough fluid in your body, ADH is released, and your kidneys keep the extra fluid instead of releasing it into your bladder. In central diabetes insipidus, the pituitary or hypothalamus is damaged, resulting in issues with the release and/or production of ADH. The pituitary and/or hypothalamus can be damaged due to tumors, head injuries, brain lesions, surgeries, or inherited problems.

Cross section of the brain. Note the location of the pituitary and hypothalamus
HP

  • Gestational diabetes insipidus - You may have heard that some women develop diabetes during pregnancy, which is far more common than developing diabetes insipidus. In very rare cases, the placenta (the organ that provides nourishment for the unborn baby) can actually destroy the mother's ADH, which results in diabetes insipidus.
  • Primary polydipsia - Drinking too much water can also cause diabetes insipidus. If you drink too much water, it actually can prevent your body from making ADH. The cause of this can be mental illness or issues with the hypothalamus, which regulates how much you want to drink.
  • Nephrogenic diabetes insipidus - The word 'nephros' means kidney in Greek, so this type of diabetes insipidus results from issues with the kidneys, specifically the tubules. The tubules are the part of the kidney that allows fluid to be released or absorbed. Damage to the tubules prevents the kidneys from doing what the ADH tells them to do. The damage can be genetic or caused by drugs like antiviral medication or lithium.

Case Study Answered

Based on the various causes of diabetes insipidus, there are a few possibilities for our three-year old. Doctors need to confirm that it is diabetes insipidus, so they may perform a water deprivation test. Like the name implies, it is a test that withholds water. This is done while measuring ADH levels and observing urine output, including how diluted the urine appears. Doctors will likely order an MRI and/or a CT scan to look at the brain to see if damage to the hypothalamus or pituitary has occurred. If it is believed to be genetic, doctors will perform genetic testing.

In the case of our three-year old boy, doctors have found damage to his pituitary gland and lesions on the skull through the MRI and CT. After taking a sample from one of the skull lesions, doctors identified the culprit as Langerhans Cell Histiocytosis, or LCH. While LCH is rare, it is often seen in children aged 1 to 3 and is caused by overactive immune cells that can actually eat through bones and tissues, including the pituitary gland. One of the signs doctors look for in LCH is diabetes insipidus, so the two often go together especially in young children.

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