Endocrine Abstracts

Introduction: Central diabetes insipidus is characterized by partial or total ADH deficit of various origins. The clinical picture is dominated by massive polyuria with diluted urine, increased thirst and daily water consumption reaching impressive quantities.

Case report: We report the case of a 16 year-old male teenager presenting with excessive thirst and water intake of 8 -10 l/day and voiding large quantities of diluted urine. Symptoms started gradually over the past 3 years. He attributes his increased thirst to increased transpiration during his recently restarted judo-training and he states he can abstain from drinking water if he has to, especially during school-time. He denies headaches and troubled vision. Physical examination was unremarkable, except for a grade 1 obesity (BMI 32 kg/m²) of recent onset (interruption of regular training during first COVID lock-down). Personal history is devoid of chronic diseases and head trauma and he denies consumption of medication or recreational drugs. Family history is positive for type 2 diabetes in all his four grandparents. Lab tests including electrolytes and pituitary axis returned normal. A thirst test was undertaken, starting at 23.00 h and conducted until 12 p.m. next day. Sodium concentration increased from 140 to 143 mEq/l, serum osmolality increased from 284 to 294 mOsm/l, while urine osmolality raised slightly from 602 to 679 mOsm/kg. No signs of dehydration and no hypotension occurred during the test. At the final blood draw copeptine was measured at an external laboratory. Patient was discharged with no treatment awaiting the results of hypophysis IRM and copeptine. At the follow-up, he still reports a water intake of 3 to 7 l per day. The IRM of the hypophysis and IgG4 level were normal. Copeptine measured at 1.7 pmol/l for a osmolality of 294 mOsm/l (normal range 2.3-24.5 pmol/l for osmolality between 291 and 295 mOsm/kg) thus showing insufficient increase and suggesting a partial deficit of ADH. Arginin- vasopressin was initiated at a dose of 25 microg/day sublingual in the morning. At one–week follow-up water consumption decreased to 1.5-2 l/day, urine output normalized, while maintaining normal sodium and serum osmolality.

Conclusion: The copeptine value and the response to the therapeutic trial of arginine-vasopressin helped diagnosing a central partial ADH deficit which we considered idiopathic, however repeated minor head trauma during his years-long judo-training may have also played a role in the onset of the disease.