Nephrogenic diabetes insipidus is a long name for an uncommon condition. Nephrogenic diabetes insipidus is not the same as diabetes mellitus. Diabetes mellitus causes elevated blood sugar levels. But nephrogenic diabetes insipidus is due to a problem in the kidneys.
In nephrogenic diabetes insipidus, the kidneys can't respond to a hormone that regulates fluid balance. Excessive urination and thirst are the results. Nephrogenic diabetes insipidus can be challenging to treat.
What is nephrogenic diabetes insipidus?
Diabetes insipidus is caused by problems related to a hormone called antidiuretic hormone or ADH. ADH is produced in a part of the brain called the hypothalamus. It's stored in the pituitary gland. Release of ADH is triggered by fluid loss or dehydration. When it's released, it causes the kidneys to retain water. This results in a decrease and concentration of urine.
In nephrogenic diabetes insipidus, enough ADH is produced. But the kidneys are partially or completely blind to it. Typically, the kidneys' ADH sensors are missing or defective. As a result, ADH flows by without effect. The kidneys don't absorb enough water. Instead, they excrete abundant dilute urine as if no ADH were present.
What are the symptoms of nephrogenic diabetes insipidus?
The lack of ability by the kidneys to conserve water leads to the symptoms of nephrogenic diabetes insipidus. They include:
- Excessive thirst
- Excessive urine production (polyuria).
In some people, these symptoms can become extreme and cause dehydration. Excessive fluid losses can also cause electrolyte imbalances. Symptoms of electrolyte imbalances include:
- Unexplained weakness
- Muscle pains
For someone without nephrogenic diabetes insipidus, the extreme thirst it creates can be hard to understand. Some people need to drink a large glass of liquid every 15 minutes, all day, every day. And since the kidneys aren't holding that water in, that means a lot of bathroom breaks.
But why "insipidus"? People with diabetes insipidus aren't insipid, but their urine is. Insipid can mean dull or lacking flavor. Believe it or not, doctors long ago would taste urine to detect illness. Unlike diabetes mellitus, which results in sweet tasting urine, diabetes insipidus creates watery, flavor-free urine.
What are the causes of nephrogenic diabetes insipidus?
In infants, nephrogenic diabetes insipidus is most commonly caused by an inherited genetic mutation present at birth. As a result, the receptor for ADH doesn't function properly.
In adults who develop nephrogenic diabetes insipidus, genetics aren't the cause. Instead, medicines or electrolyte abnormalities cause the condition. Causes of nephrogenic diabetes insipidus in adults include:
- Lithium, a drug most commonly taken for bipolar disorder; up to 20% of people taking lithium will develop nephrogenic diabetes insipidus.
- Other medicines, including demeclocycline (Declomycin), ofloxacin (Floxin), orlistat (alli, Xenical), and others
- High levels of calcium in the blood (hypercalcemia)
- Low levels of potassium in the blood (hypokalemia)
- Kidney disease, especially polycystic kidney disease
The other form of diabetes insipidus is known as central diabetes insipidus. In central diabetes insipidus, the kidneys function normally, but not enough ADH is produced in the brain. Central diabetes insipidus has similar symptoms to nephrogenic diabetes insipidus. However, central diabetes insipidus can be treated by replacing ADH with a medication called desmopressin.
How is nephrogenic diabetes insipidus treated?
Nephrogenic diabetes insipidus can be difficult to treat. Since the kidneys can't respond to ADH, giving more ADH doesn't help. There's no good way to get the kidneys to respond to the ADH that's there. In fact, treatment options are limited.
If a drug like lithium is responsible, switching medicines might improve nephrogenic diabetes insipidus.
Most adults with nephrogenic diabetes insipidus are able to keep up with fluid losses by drinking water. For some people, though, the symptoms of near-constant thirst and urination can become intolerable. Some treatments can reduce the symptoms of nephrogenic diabetes insipidus, at least somewhat:
- Diet. A low-salt, low-protein diet reduces urine output.
- Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen (Motrin), indomethacin (Indocin), and naproxen (Naprosyn) also can reduce urination.
- Diuretics. It might seem paradoxical, but "water pills" like hydrochlorothiazide and amiloride can ease excessive urination from nephrogenic diabetes insipidus.
All adults and children with nephrogenic diabetes insipidus should take frequent bathroom breaks. This helps to avoid over-distending the bladder, which can cause long-term problems, though rarely.
The most important treatment for nephrogenic diabetes insipidus is to ensure constant access to lots of water. Not keeping up with fluid losses can lead to dehydration or electrolyte imbalances, which can sometimes be severe. Seek medical help if symptoms don't improve after rehydrating, eating fresh fruit, and taking a multivitamin.