''Non-sweet'' diabetes of pregnancy

Article Abstract:

Although increased urination is common in pregnancy, polyuria (voiding of very large quantities) and polydipsia (excessive thirst) in pregnancy are usually regarded as pathological. When this is the result of diabetes insipidus (associated with abnormalities of the vasopressin system, which regulates water retention), treatment and diagnosis are complicated. An article concerning this subject appears in the February 21, 1991 issue of The New England Journal of Medicine. Diabetes insipidus can be caused by a deficiency of vasopressin (formerly called anti-diuretic hormone); or, by the kidney's resistance to the effects of vasopressin. In pregnancy, diabetes insipidus is often transient, possibly because of elevated levels of vasopressinase (an enzyme that inactivates vasopressin). Other possible causes are discussed. Pregnancy decreases the threshold for thirst, leading to increased drinking in patients who have asymptomatic nephrogenic (associated with the kidneys) diabetes insipidus. In normal pregnancies, this threshold change is accompanied by accommodations in the vasopressin system that keep urine volume within bounds. Simply lowering the thirst threshold (controlled by the body's ability to sense plasma osmolality, a measure of the concentration of certain substances in plasma) does not automatically cause the correct amount of vasopressin that is released, however; sodium levels must also be properly regulated. These levels are lower during pregnancy. While the effects of lowered thresholds for thirst and vasopressin secretion in pregnancy are well characterized, the control mechanisms for these changes are not understood. (Consumer Summary produced by Reliance Medical Information, Inc.)

Care and treatment, Pregnant women, editorial

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Aggravation of subclinical diabetes insipidus during pregnancy

Article Abstract:

The cases of two pregnant women are presented who developed transient polyuria (increased urinary volume) and polydipsia (excessive thirst) during pregnancy, which normalized after delivery. In one case, the symptoms began during the second trimester of pregnancy; in the other, during the third. The patients underwent testing to determine the probable cause of these symptoms. Results showed that the women had subclinical diabetes insipidus, the disease was present, but no symptoms were apparent; the disorder was aggravated by pregnancy. One patient had elevated levels of vasopressin (anti-diuretic hormone, involved in water retention), which failed to affect the kidney in a normal manner; thus, her diabetes insipidus was of nephrogenic origin. The second patient had an inadequate vasopressin response to stimuli that normally elicit it (hypertonic solutions); her condition was of neurogenic origin. The reason pregnancy sometimes unmasks diabetes insipidus is not known, but possible hypotheses are discussed briefly. Vasopressinase, an enzyme that inactivates vasopressin, and normally increases during pregnancy, may be involved. Pregnant patients who develop polyuria and polydipsia should be monitored after delivery for the development of diabetes insipidus. (Consumer Summary produced by Reliance Medical Information, Inc.)

Case studies, Development and progression

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Urinary excretion of aquaporin-2 in patients with diabetes insipidus

Article Abstract:

It may be possible to determine what type of diabetes insipidus a patient has based on the changes in aquaporin-2 levels in the urine after taking vasopressin. Vasopressin is a hormone that increases urine concentration. Aquaporin-2 is a protein that transports water across membranes in the kidney. In 5 normal men, urinary levels of aquaporin-2 decreased from 11.2 pmol per milligram of creatinine following dehydration to 3.9 pmol per milligram of creatinine after drinking 1 liter of water. In another 6 normal people, aquaporin-2 levels went from 0.8 to 11.2 pmol per milligram of creatinine after receiving desmopressin, which is composed of desamino and arginine vasopressin. In 5 patients with central diabetes insipidus, aquaporin-2 levels increased by 4 to 6 times from a base level of 0.4 pmol per milligram of creatinine after receiving vasopressin. However, in 4 patients with genetically determined diabetes insipidus, aquaporin-2 levels did not change in response to vasopressin. Thus, patients with this rarer form of the disease do not appear to respond to vasopressin.

Vasopressin, Vasopressins

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