Effect of an oral glucose load on PTH, 250HD3, calcium, and phosphorus homeostasis in postmenopausal women.

INTRODUCTION. Previous studies particularly in children and neonates have shown that serum calcium declines and parathyroid hormone (PTH) rises during an oral glucose load. However, there is not a general agreement in this regard. This study was carried out to evaluate the effects of an oral glucose load on calcium and phosphorus homeostasis in postmenopausal women along with serum insulin, PTH, and 250HD3 changes. PATIENTS AND METHODS. After an overnight fasting, an oral glucose tolerance test was performed in 50 postmenopausal women; and glucose, insulin, PTH, and D3 were measured at baseline and every 30 min during the 2 hours of the test. RESULTS. Serum glucose and insulin increased as expected and reached their peak values at 60 and 90 min, respectively. PTH and phosphorus decreased significantly and the maximum decline was observed at 30 and 120 min after glucose load (p < 0.0001), respectively. Serum calcium, magnesium, and D3 levels showed no significant changes at any time measured. Serum PTH values had a significant negative correlation with glucose and insulin values (p = 0.026 and p = 0.031, respectively). Serum D3 also correlated negatively with glucose (p = 0.002). CONCLUSION. Our study shows that an oral glucose load induced hyperglycemia/hyperinsulinemia promotes a significant decline in serum PTH and phosphorus levels without changes in calcium or 250HD3 in postmenopausal women.