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Diabetes Insipidus
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10.21.06 (1 year ago)
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Definition
Diabetes insipidus is caused by the inability of the kidneys to conserve water, which leads to frequent urination and pronounced thirst.
Causes, incidence, and risk factors
Diabetes insipidus (DI) is an uncommon condition that occurs when the kidneys are unable to conserve water as they perform their function of filtering blood. The amount of water conserved is controlled by antidiuretic hormone (ADH), also called vasopressin.
ADH is a hormone produced in a region of the brain called the hypothalamus. It is then stored and released from the pituitary gland, a small gland at the base of the brain.
DI caused by a lack of ADH is called central diabetes insipidus. When DI is caused by failure of the kidneys to respond to ADH, the condition is called nephrogenic diabetes insipidus. The major symptoms of diabetes insipidus are excessive urination and extreme thirst. The sensation of thirst stimulates patients to drink large amounts of water to compensate for water lost in the urine.
Central diabetes insipidus is caused by damage to the hypothalamus or pituitary gland as a result of surgery, infection, tumor, or head injury. Although rare, central DI is more common than nephrogenic DI.
Nephrogenic DI involves a defect in the parts of the kidneys that reabsorb water back into the bloodstream. It occurs less often than central DI. Nephrogenic DI may occur as an inherited disorder in which male children receive the abnormal gene that causes the disease on the X chromosome from their mothers.
Nephrogenic DI may also be caused by diseases of the kidney (for example, polycystic kidney disease) and the effects of certain drugs (for example, lithium, amphotericin B, demeclocycline).
If thirst mechanisms are normal and adequate fluids are consumed, there are no significant effects on body fluid or salt balance. If inadequate fluids are consumed, the large amount of water lost in the urine may cause dehydration and high sodium levels in the blood.
Symptoms
• Excessive thirst
o May be intense or uncontrollable
o May involve a craving for ice water
• Excessive urine volume
Signs and tests
• Urinalysis
• Urine output:
o Central DI -- urine output suppressed by a dose of ADH
o Nephrogenic DI -- urine output not suppressed by a dose of ADH
• MRI of the head
Complications
Inadequate fluid consumption can result in the following complications:
• Dehydration
o Dry skin
o Dry mucous membranes
o Sunken appearance to eyes
o Sunken fontanelles (soft spot) in infants
o Fever
o Rapid heart rate
o Unintentional weight loss
• Electrolyte imbalance
o Fatigue, lethargy
o Headache
o Irritability
o Muscle pains
Treatment
The cause of the underlying condition should be treated when possible.
Central diabetes insipidus may be controlled with vasopressin (desmopressin, DDAVP). Vasopressin is administered as either a nasal spray or tablets.
Vasopressin is ineffective for patients with nephrogenic DI. In most cases, if nephrogenic DI is caused by medication (for example, lithium), stopping the medication leads to recovery of normal kidney function.
Hereditary nephrogenic DI is treated with fluid intake to match urine output and drugs that lower urine output. Drugs used to treat nephrogenic DI include the anti-inflammatory medication indomethacin and the diuretics hydrochlorothiazide (HCTZ) and amiloride.
Expectations (prognosis)
The outcome depends on the underlying disorder. If treated, diabetes insipidus does not cause severe problems or reduce life expectancy.
Hyperglycemia
Hyperglycemia or High Blood Sugar is a condition in which an excessive amount of glucose circulates in the blood plasma. The term is from Greek: hyper-, prefix meaning "too much"; -glyc-, root meaning "sweet"; -emia, suffix meaning "of the blood".
Causes
Diabetes
Hyperglycemia is one of the classic symptoms of diabetes mellitus, the others being frequent and excessive thirst accompanied by frequent and excessive urination. But caution: A hyperglycemic condition without other classic symptoms is not dispositive of a diagnosis of diabetes mellitus, but hyperglycemia is also an independent medical condition with other causes.
By comparison to hyperglycemia as an independent non-diabetic condition, Diabetes mellitus, in its organic form, is an apparently auto-immune disease of unknown cause and unknown cure, in which the Islets of Langerhans (a subordinate organ within the pancreas) fail to produce sufficient quantities of the hormone insulin or produce no insulin at all.
Non-organic diabetes mellitus can be caused by accidental damage to the islets of Langerhans, or to the pancreas itself (the islets being subordinate, they cannot function without the pancreas); or by other diseases affecting the pancreas, such as pancreatic cancer and other causes of pancreatic failure (which, thus, causes the islets to fail); or by surgical removal of the pancreas (thus, of the islets), usually for one of the reasons noted above.
Non-diabetic hyperglycemia
The most common cause of chronic non-diabetic hyperglycemia is obesity, the cure for which is proper diet and exercise to reduce the body's excess white fat reserves. The presence of excessive white fat reserves interferes with the body's ability to properly absorb and use insulin that is otherwise produced in sufficient quantity. Chronic non-diabetic hyperglycemia can produce some of the same complications as diabetic hyperglycemia; however, some of the complications of diabetes mellitus (especially juvenile-onset diabetes mellitus) can occur even if blood sugar levels are kept under control, because the disease operates beyond just the condition of hyperglycemia.
Certain eating disorders can produce acute non-diabetic hyperglycemia, as in the binge phase of bulimia nervosa, when the subject consumes an incredible number of calories at once, frequently from foods that are high in both simple and complex carbohydrates - the body simply having a fierce craving for the energy that carbohydrates provide.
History
Diabetes is Greek for "passing through" (i.e., frequent and excessive thirst and urination; and Mellitus is Latin for "honey-sweet.") Historically, diabetes was a collective name for a number of diseases, each of which affected a different endocrine gland but all of which had in common the classic symptoms of frequent and excessive thirst accompanied by frequent and excessive urination. Except for diabetes mellitus and diabetes insipidus, the other diabetic diseases have been renamed.
Measurement
Glucose levels are measured in either:
1. Milligrams per deciliter (mg/dL), in the United States and other countries (Myanmar, Liberia) that do not yet use the International or "Metric" System of measurement; or,
2. Millimoles per liter (mmol/L) in the rest of the "metrified world."
Comparatively:
• 72 mg/dL = 4 mmol/L
• 90 mg/dL = 5 mmol/L
• 108 mg/dL = 6 mmol/L
• 126 mg/dL = 7 mmol/L
Glucose levels vary before and after meals, and at various times of day; and what is "normal" varies among medical professionals, and can vary between patients. (As in other facets of life, the "average patient" does not exist as a real person.) In general, the "home" normal range for most people is about 80 to 120 mg/dL or 4 to 7 mmol/L.
A subject with a "home" range above 126 mg/dL or 7 mmol/L is generally held to have hyperglycemia, whereas a "home" range below 70 mg/dL or 4 mmol/L is considered hypoglycemic.
In fasting adults, blood plasma glucose should not exceed 126 mg/dL or 7 mmol/L. Sustained higher levels of blood sugar cause damage to the blood vessels and to the organs they supply, leading to the complications of diabetes.
Common Symptoms of Diabetic Hyperglycemia
If you have diabetes mellitus, the presence of these symptoms can indicate that blood sugar levels are too high:
• Polyphagia (frequent hunger, especially pronounced hunger)
• Polydipsia (frequent thirst, especially excessive thirst)
• Polyuria (frequent urination, especially excessive urination)
But caution: Frequent hunger without the other two symptoms (which invariably occur together, absent renal complications, bladder infections, etc.), can also indicate that blood sugar levels are too low. This commonly occurs when people who have type 2 diabetes mellitus take too much oral hypoglycemic medication for the amount of food they eat. The resulting drop in blood sugar level to below the normal range prompts a hunger response. This hunger is not usually as pronounced as in type 1 diabetes mellitus (especially the juvenile onset form).
People with chronic non-diabetic hyperglycemia who take oral hypoglycemic medication can have the same problem (again, not as pronounced a hunger. In particular, if the hyperglycemia is caused by obesity, prescription of oral hypoglycemic medication can be ill advised. This is because the medication typically interferes with the subject's weight reduction plan by artificially lowering the blood sugar levels, so that a strong hunger response occurs when the subject attempts to naturally lower the blood sugar levels through a programme of proper diet and exercise. A vicious cycle can result, in which the more the subject exercises to lose weight, the greater the hunger caused by the medication, so that subject eats more to compensate for the oral hypoglycemic and, thus, cannot lose weight. The average blood sugar levels thus do not change, which can lead to an increase in the dosage of the oral hypglycemic medication, which only perpetuates the problem.
Other symptoms of diabetic hyperglycemia may include:
• Blurred vision
• Fatigue
• Weight loss
• Poor wound healing (cuts, scrapes, etc.)
• Dry mouth
• Dry or itchy skin
• Impotence (male)
• Recurrent infections such as vaginal yeast infections, groin rash, or external ear infections (swimmers ear)
These symptoms do not normally occur with acute non-diabetic hyperglycemia (it just doesn't last long enough), but some of them can occur in chronic non-diabetic hyperglycemia. The notable exception is weight loss, which almost never happens in chronic non-diabetic hyperglycemia - especially if the hyperglycemia is caused by obesity. Instead, the subject either maintains a stable obese weight, or gains weight. This is one of the ways non-diabetic hyperglycemia can be distinguished from diabetic hyperglycemia.
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