Investigation of the Relationship of Vitamin D, Parathyroid Hormone, Calcium Serum Level, and Insulin Resistance among Obese Individuals

Abstract

Objective: Several studies have shown that 25-hydroxyvitamin D, parathyroid hormone (PTH), and serum calcium (Ca) may play functional roles with insulin resistance.Methods: This case–control study included 60 obese individuals with impaired fasting glucose who were compared with 60 non-obese individuals with normal fasting glucose who visited the endocrinology and metabolism department. Fasting plasma glu-cose, fasting insulin, triglyceride, PTH, and serum 25-hydroxyvitamin D (25(OH)D) were measured from all subjects in the morning after approximately 8 h of fasting using methods with respect to the standard operating procedures. Homeostatic model assess-ment of insulin resistance (HOMA-IR) was used for determining insulin resistance. The statistical analysis was attained by SPSS.Results: A lack of association was found between serum 25(OH)D and insulin resistance (HOMA-IR) before and after adjusting PTH, Ca, and various variables either in all participants or after exclusion of participants with HOMA-IR ≤2.5. On the other hand, PTH showed a significant inverse correlation with fasting insulin (p=0.022) and HOMA-IR (p=0.023) after adjusting 25(OH)D, serum Ca, and various variables and exclusion of participants with HOMA-IR ≤2.5.Conclusion: In the present study, we did not find a relationship between insulin resistance and vitamin D levels. Further studies are needed for clarifying the relationship between insulin resistance and vitamin D levels.