Acute PTH response to oral calcium load and seasonal variation of vitamin D status in healthy young adult subjects
Guillemant, J.; Guillemant, S.
European Journal of Clinical Nutrition 50(7): 469-472
1996
ISSN/ISBN: 0954-3007 PMID: 8862484 Document Number: 467568
Objective: The aim of the present study was to check the relationship between seasonal variations of vitamin D status and parathyroid function explored both in basal conditions and after oral calcium load. Design: The calcium and parathyroid hormone response to the intake of calcium load was studied at two different seasons, before winter (November) and after winter (March-April), corresponding to different vitamin D status. Subjects: Eighteen healthy young male adults (age: 25 +- 3 y) were studied. All were medical students who were selected as having no disorders known to affect calcium metabolism. Intervention: At each period an oral calcium load (1 g of elemental calcium as calcium carbonate) was administered. Blood samples were collected before and 1 h, 2 h, 3 h and 4 h after the intake of calcium. Serum ionized calcium (Ca-2+) and intact parathormone (PTH1-84) were measured at each time point and 25-hydroxyvitamin calcium test. In D (25(OH)D) was measured before each Results: After winter, basal 25(OH)D concentrations were decreased (from 16.4 +- 6.6 to 11.5 +- 4.4 mu-g/l) and basal PTH concentrations were increased (from 24.1 +- 6.5 to 31.7 +- 9.1 pg/ml), and the difference between pre- and post-winter basal concentrations were statistically significant for both variables (P lt 0.001). A statistically significant negative correlation between PTH and 25(OH)D was obtained both before (r = -0.63; P 0.005) and after (r = 0.64; P = 0.004) winter. The maximum decrement in PTH (DELTA-PTH-max) was not different before (13.92 +- 4.58 pg/ml) and after (14.14 +- 7.79 pg/ml) winter, but as a consequence of post-winter higher basal levels of PTH, at all time points after oral calcium load, concentrations of PTH after winter were significantly higher than before. Conclusions: The present results show that PTH concentrations are physiologically linked to 25(OH)D concentrations, and emphasize the need of taking into account the vitamin D status of each subject to predict the effect of an oral calcium load on absolute concentrations of PTH. Sponsorship: Universite Pierre et Marie Curie (Paris VI).