Relationships of Serum Osteocalcin, 25-Hydroxyvitamin D, and Parathyroid Hormone with Glycaemic and Lipid Indices in Type 2 Diabetes Mellitus

Introduction: Type 2 diabetes mellitus (T2DM) is a multifactorial metabolic disorder characterized by chronic hyperglycemia and is frequently associated with dysregulated bone and mineral metabolism. Emerging evidence suggests a complex interplay between osteocalcin, vitamin D, and parathyroid hormone (PTH) in the regulation of glucose and lipid homeostasis. Design: This investigation employed a cross-sectional study design. Methods: A cross-sectional study was conducted involving 200 participants: 100 patients with T2DM and 100 age- and sex-matched healthy controls. Fasting blood glucose (FBS), postprandial blood glucose (PPBS), HbA1c, lipid profile, serum osteocalcin, vitamin D3, and PTH were measured using standardized biochemical assays. Participants were stratified according to PTH, vitamin D3, and osteocalcin levels, and correlations with glycemic and lipid indices were analyzed. Results: T2DM patients with elevated PTH (>65 pg/mL) showed significantly higher FBS and HbA1c levels as well as lower vitamin D3 concentrations compared with those with normal PTH (p < 0.05). Stratification by vitamin D3 revealed higher PTH levels in vitamin-D-deficient individuals (<20 ng/mL), while osteocalcin distribution showed no significant association with PTH. Correlation analysis demonstrated positive associations of HbA1c with PTH and negative associations with vitamin D3 in both T2DM patients and controls. FBS correlated positively with triglycerides, supporting a link between hyperglycemia and dyslipidemia. Osteocalcin did not show significant correlations with glycemic or lipid parameters, suggesting that its regulation may occur through independent pathways. Conclusion: These findings highlight a strong inverse relationship between vitamin D3 and PTH and underscore their significant associations with glycemic control in T2DM. Vitamin D deficiency and secondary hyperparathyroidism appear to exacerbate adverse metabolic outcomes, whereas osteocalcin does not exert a direct influence on glycemic or lipid indices in this cohort. Collectively, the data emphasize the necessity of maintaining optimal vitamin D status for managing T2DM-related metabolic disturbances.