A-039 Parathyroid Hormone and Vitamin D Follow an Inversely Correlated Serum Level

Abstract

Abstract Background Parathyroid hormone (PTH) is a polypeptide responsible for regulating the physiological level of serum calcium through a complex homeostatic process closely associated with bone metabolism. In response to a decreased serum concentration of calcium, PTH level is increased leading to the elevation of calcium via bone resorption. Furthermore, Vitamin D (Vit-D) is a critical component of the endocrine system that also contributes to calcium homeostasis. Vit-D increases the level of serum calcium by stimulating intestinal absorption and renal reabsorption. Vit-D impacts the serum level of PTH by two distinct mechanisms. First indirectly, an increase in serum concentration of calcium, caused by Vit-D-mediated intestinal absorption and renal reabsorption disengages the process of PTH release through interaction with calcium-sensing receptors on parathyroid cells. Secondly, Vit-D directly interacts with parathyroid cells resulting in a reduced expression of PTH. Taken together, Vit-D is assumed to negatively impact the serum level of PTH. This study examined the homeostatic correlation between the circulating concentrations of Vit-D and PTH. Methods Retrospective serum concentrations of PTH and Vit-D were retrieved from the biochemical profiles of hospitalized and ambulatory patients who presented to or admitted at the tertiary care level hospital of University of Texas Southwestern Medical Center during the period between July-to-September of 2021. Correlation analysis between Vit-D and PTH was performed using GraphPad-PRISM-version-8. Results A total of 163 corresponding serum Vit-D and PTH values were obtained. Vit-D and PTH values displayed an inverse correlation (Figure 1). Pearson r values for linear and logarithmic trendlines (-0.6745 and -0.785, respectively) demonstrated a negative correlation between Vit-D and PTH. Conclusions Measuring Vit-D and PTH levels are critically important for assessing the homeostatic status of calcium. PTH level maintains an inverse relationship with Vit-D. Therefore, therapeutic targeting of Vit-D or PTH would mutually affect their concentration eventually reflected in calcium homeostasis.