Central Diabetes Insipidus in a Dog with a Pro-Opiomelanocortin-Producing Pituitary Tumor not Causing Hyperadrenocorticism

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Title: Central Diabetes Insipidus in a Dog with a Pro-Opiomelanocortin-Producing Pituitary Tumor not Causing Hyperadrenocorticism
Authors: Goossens, Marielle M.C.; Rijnberk, Ad; Mol, Jan A.; Wolfswinkel, Jeannette; Voorhout, George
Publisher: Journal of Veterinary Internal Medicine
Date Published: September 1995 - October 1995
Reference Number: 56
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Abstract • Translation
Central diabetes insipidus was diagnosed by vasopressin measurements during hypertonic stimulation in a 9-year-old male giant Schnauzer with polyuria and polydipsia. The impaired release of vasopressin was believed to be caused by a large pituitary tumor, which was visualized by computed tomography. Studies of the function of the anterior lobe and the pars intermedia of the pituitary gland were conducted, and high concentrations of ACTH and alpha-melanotrophic hormone (alpha-MSH) were found without concomitant hyperadrenocorticism. Studies of the molecular size of the immunoreactive ACTH in plasma by gel filtration revealed that most of the circulating immunoreactivity was not ACTH but its precursor pro-opiomelanocortin (POMC) and low-molecular-weight POMC-derived peptides. The pituitary tumor of this dog probably originated from melanotrophic cells of the pars intermedia. The sensitivity of the pituitary-adrenocortical system for the suppressive effect of dexamethasone was unaffected.

This translation by the NDI Foundation is to assist the lay reader. To provide a clear, accessible interpretation of the original article, we eliminated or simplified some technical detail and complicated scientific language. We concentrated our translation on those aspects of the article dealing directly with NDI. The NDI Foundation thanks the researchers for their work toward understanding and more effectively treating this disorder.
© Copyright NDI Foundation 2007 (JC)

Goossens, et al., report on a 9-year-old male giant Schnauzer that was brought to them suffering from polyuria (the chronic passage of large volumes of urine) and polydipsia (chronic excessive intake of water). After eliminating the possibility of several common causes of polyuria and polydipsia, the authors determined the dog had central diabetes insipidus (CDI), a condition caused by the inability of the neurohypophyseal system (the posterior lobe of the pituitary gland) to produce or release sufficient amounts of the antidiuretic hormone, vasopressin (VP).

In this instance the inability of the dog's neurohypophyseal system to produce or deliver VP was caused by a large pituitary tumor. The dog was treated with desmopressin acetate (DDAVP), a synthetic vasopressin analogue. This reduced the dogs polyuria and polydipsia to the satisfaction of the dog's owner.