Effect of acute oral calcium load on serum PTH and bone resorption in young healthy subjects: an overnight study

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Abstract
Objective: To investigate the effects of a 400 mg acute oral calcium dose on PTH and bone resorption markers in a young, healthy population. Design: Fasting serum parathyroid hormone (PTH), C-telopeptides (CTX), total calcium (Ca), albumin and urinary calcium/creatinine ratio (uCa/Cr) were measured on two separate days: one before and the other 10 h after oral administration of 400 mg calcium. Serum 25-hydroxy vitamin D (25-OHD) status was assessed at baseline. Dietary calcium intake was assessed using a food frequency questionnaire (FFQ). Subjects: A total of 32 healthy, young adults (17 female, 15 male; mean±s.e.m. age: 21±1 y) took part in this study. Their mean (s.e.m.) calcium intake was 1125 (±56) mg/day. Intervention: Effervescent Sandocal® 400 tablets dissolved in water. Results: After the calcium challenge, mean Ca and uCa/Cr ratio increased significantly, and both PTH and CTX concentrations were significantly lower. Multiple regression analysis showed no relationship between the response to the 400 mg load and previous dietary calcium intake (as assessed by FFQ) or serum 25-OHD. Conclusion: We have shown that in a young, healthy population, 400 mg oral calcium can inhibit bone resorption (as measured by serum CTX) and PTH, and this appears to be independent of previous dietary calcium intake and vitamin D status. Sponsorship: None.