Association of Serum Prolactin Levels in Patients with Type 2 Diabetes Mellitus with and without Diabetic Nephropathy

Abstract Introduction: Diabetic nephropathy (DN), a common microvascular complication of type 2 diabetes mellitus (T2DM), contributes significantly to chronic kidney disease and is associated with increased morbidity. Prolactin (PRL), a hormone classically linked with lactation, has emerging roles in metabolism and renal physiology. While alterations in PRL levels in T2DM are documented, the independent association between PRL and DN remains unclear. Objective: This study aimed to evaluate the independent association between serum PRL levels and the presence of DN in patients with T2DM. Materials and Methods: A hospital-based cross-sectional study was conducted among 250 T2DM patients. DN was defined by the urine albumin–creatinine ratio. Serum PRL was measured by chemiluminescent immunoassay, with sex-specific reference ranges (males: 3.31–19.80 ng/mL; females: 5.4–24.2 ng/mL). Macroprolactin was not excluded, which is a methodological limitation. Results: Median serum PRL was higher in DN patients (13.25 ng/mL, interquartile range [IQR] = 8.9–20.2) versus non-DN (11.3 ng/mL, IQR = 7.6–14.5; P = 0.001, Mann–Whitney U test). Mean levels (±standard deviation) were 16.99 ± 13.84 ng/mL (DN) versus 12.48 ± 6.52 ng/mL (non-DN). Logistic regression confirmed PRL as an independent predictor of DN (adjusted odds ratio = 1.12 per 1 ng/mL increase; 95% confidence interval = 1.05–1.20; P < 0.001). Subgroup analysis showed stronger associations in poor glycemic control (hemoglobin A1c >10%). Conclusion: Serum PRL is independently associated with DN in T2DM, even after adjusting for confounders. Furthermore, studies excluding macroprolactin and using a longitudinal design are warranted.