Objective To investigate the mediating role of serum vitamin D₃ levels in the relationship between depression severity and cognitive function among elderly individuals with mild cognitive impairment (MCI). Methods A total of 477 elderly individuals with MCI who met the inclusion criteria were recruited via convenience sampling from the Health Service Center of Matang Street Community, Yijiang District, Wuhu City, Anhui Province, between January 2023 and December 2023. Data were collected using a general questionnaire, the Geriatric Depression Scale, and the Mini-Mental State Examination. Serum vitamin D₃ levels were measured for all participants. Pearson correlation analysis was conducted using SPSS 27.0, and the mediating effect was analyzed using Model 4 in the Process plugin. Results Cognitive function in elderly individuals with MCI was negatively correlated with depression severity (P<0.001) and positively correlated with serum vitamin D₃ levels (P<0.05). Bootstrap test results indicated that serum vitamin D₃ levels partially mediated the relationship between depression and cognitive function in elderly individuals with MCI, with a mediating effect of -0.019 (95% CI: -0.038 to -0.005), accounting for 8.02% of the total effect. Conclusion Serum vitamin D₃ levels play a partial mediating role in the relationship between depression and cognitive function in elderly individuals with MCI.

Objective To observe the effects of high dose calcitriol combined with low calcium dialysis on serum levels of iPTH, calcium and phosphorus. Methods Twenty patients with maintenance hemodialysis and SHPT were treated with high dose calcitriol combined with low calcium dialysis for four weeks. The changes of serum levels of iPTH, calcium and phosphorus were compared before and after treatment. Results After four weeks of treatment, the serum iPTH value of patients decreased significantly, the difference was statistically significant (P<0.01), while the serum levels of total calcium and phosphorus were higher than those before treatment, but the difference was not statistically significant (P>0.05). Conclusion Short-term use of high dose calcitriol therapy combined with low-calcium dialysis can significantly reduce the level of serum iPTH, while the level of serum calcium and phosphorus is not significantly increased. This method is safe and effective.