Central diabetes insipidus: pathophysiology, diagnosis, and modern approaches to the treatment of antidiuretic hormone deficiency

Background. Polydipsia-polyuria syndrome is characterized by abnormally increased fluid intake by the patient, which often mimics the manifestations of central diabetes insipidus (syn. – antidiuretic hormone deficiency). However, the differences between these two conditions are fundamental, as treatment approaches differ significantly: true central diabetes insipidus requires replacement therapy with an antidiuretic hormone analog, desmopressin, whereas polydipsia-polyuria syndrome is often associated with primary polydipsia and requires a different treatment approach. Correct diagnostic tactics play a key role, as misdiagnosis and inappropriate treatment can lead to serious complications such as water intoxication (severe hyponatremia). Early detection of central diabetes insipidus allows for timely initiation of appropriate treatment, preventing the development of dehydration, and minimizing the negative impact of the disease on the patient's daily life. Results. This review presents a modern algorithm for the differential diagnosis of polydipsia-polyuria syndrome. This involves initial confirmation of hypotonic polyuria and exclusion of common causes of nephrogenic diabetes insipidus. Subsequently, functional tests aimed at ruling out primary polydipsia (patients healthy in terms of ADH secretion) are performed, including fluid deprivation and hypertonic saline. A desmopressin test is indicated only after reliable confirmation of the diagnosis of diabetes insipidus. The various proposed variants of the above-described tests, including those modifying antidiuretic hormone release with arginine and assessing the concentration of this hormone (indirectly as copeptin) in the blood, have various limitations in implementation and interpretation and are associated with an element of overdiagnosis of central diabetes insipidus, which, from a clinical perspective, predisposes patients to the development of water intoxication when prescribed desmopressin treatment. Conclusion. Replacement therapy using desmopressin, an antidiuretic hormone analogue, is a key element in the treatment of central insufficiency and, in most cases, allows for achieving an optimal quality of life.