Endocrine Abstracts

Background

Diabetes Insipidus is a complex and heterogeneous clinical syndrome affecting water balance, resulting in large volumes of dilute urine. Determining the mechanism and etiology of diabetes insipidus, as well as differentiating it from other pathologies that cause polyuria and polydipsia has always been a challenge since water deprivation test is not always conclusive and antidiuretic hormone can not be reliably measured in the circulation.

Aim

The aim of this study is to analyze the most common causes of diabetes insipidus, and thus determine the different etiologies of this disorder.

Methods

This study was conducted using SPSS including patients who had been diagnozed with diabetes insipidus, hospitalized between 2012 and 2020 in the Endocrinology Department of Hedi Chaker university hospital, Sfax, Tunisia.

Results

A total of 20 patients were included in this study. The average age was 60 years old. 13 of them were women and 7 were men. All of our patients had polyuria and polydipsia. Only 6 of them had signs of intracranial hypertension. No signs of dehydration was found in any of our patients. The average polyuria was quantified at 7.8 l/24 h. While average polydipsia was estimated at 7.2 l /24 h. An elevated plasma osmolarity was found in only two patients, estimated at 318 and 328 mOsm/l respectively. The average urinary osmolarity was 208 mOsm/l. Only 7 of our patients undertook a water deprivation test, it was well-tolerated in 5 of them, and poorly tolerated in 2, due to extreme thirst. The water deprivation test was in favor of central diabetes insipidus in 4 patients and inconclusive in 3 others. Central diabetes insipidus was found in 19 patients, while nephrogenic diabetes insipidus was found in only one patient. A lack of posterior pituitary hyperintensity on sagittal T1-weighted imaging was found in 7 out of the 19 cases of central diabetes insipidus. Neuro-surgery was the most common cause of central diabetes insipidus, found in 10 patients, while empty sella syndrome was found in 3 patients, head trauma in 2 patients, craniopharyngioma in 1 patient, and idiopathic central diabetes insipidus in 3 patients. While the nephrogenic diabetes insipidus was linked to lithium.

Conclusion

The patient history, MRI scan and water deprivation test usually suffice to establish the cause of diabetes insipidus, but some situations remain unclear and not devoid of discrepancy. Copeptin test may offer a promising accuracy regarding diagnosing the etiologies of diabetes inspidus.