Endocrine Abstracts

Background: It has been suggested that higher arginine vasopressin (AVP) concentration may be associated with greater eGFR decline in diabetic patients not using inhibitors of the renin-angiotensin system (Diabetologia 2013). If excessive AVP action is detrimental to renal prognosis, then diabetic patients with central diabetes insipidus (CDI) may have relatively preserved renal function. Therefore, we aimed to compare long-term renal prognosis of diabetic patients with and without CDI.

Methods: We retrospectively identified 39 diabetic patients with CDI followed up at our university hospital for more than 4 years. Propensity matching for baseline age, sex, BMI, HbA1c, eGFR, SBP, DBP, urinary protein, and length of observation was performed to select 39 control diabetic patients without CDI in the same hospital.

Results: Baseline demographics of the CDI group were as follows: age 45.6 years, 41% female, BMI 27.2, HbA1c 7.0%, eGFR 90.4 ml/min/1.73 m², blood pressure 122/79 mmHg and observation of 1862 days (mean values). There was no significant difference in eGFR at the end of observation period (Control: 86.3±28.1 vs CDI: 85.8±33.7 ml/min/1.73 m²) or the slope of eGFR (Control: −0.9±3.6 vs CDI: −1.1±10.7 ml/min/1.73 m²/year) between groups. On the other hand, eGFR variability (standard deviation) was significantly greater in the CDI group (Control: 7.9±5.1 vs CDI: 18.3±13.3 ml/min/1.73 m², P<10⁻⁵). Considering that excessive fluctuations in eGFR are damaging to the kidney in general, CDI patients may exhibit milder decline in eGFR when eGFR variability and other factors, such as the use of renin-angiotensin system inhibitors, are matched between groups.

Conclusion: A simple analysis of long-term eGFR revealed no significant difference between diabetic patients with and without CDI. Nevertheless, confounding factors, such as greater eGFR variability in CDI patients, may have weakened the relationship between AVP action and decline in renal function.