Objective To determine parameters of calcium homeostasis in pregnant women with low dietary calcium intake and to observe the effects of a calcium supplement.
Method 44 pregnant women (calcium intake: 310 to 720 mg/day) were enrolled. Blood and urine samples were taken around the 20th. week (pre-treatment value). Afterwards 26 women received calcium 750 mg/day (as calcium citrate suspension) until delivery; 18 received a placebo. At 36th–38th week blood and urine samples were again taken (post-treatment value). Ca and P in serum and urine and serum bone -specific alkaline phosphatase (AP), intact PTH, 1,25–2OH-vit D, IGF-1 and degradation products of C terminal telopeptides of type I collagen (CT) were determined.
Results At enrollment serum Ca, P, AP and IGF-1 were normal although with a great individual variation for IGF-1 (50% of the women showed high values and 20% low values); PTH (103.8 ± 56.4 pg/ml), CT (4855 ± 268 pM) and 1.25–2OH-vit D (46.8 ± 7.4 pg/ml) showed high values. After treatment the calcium-treated women showed a significant decrease of AP (15.7 ± 3.3 U/l), PTH (35.8 ± 25.8 pg/ml), CT (2490 ± 1498 pM) and 1,25–2OH-vitD (38.0 ± 8.0 pg/ml) while the other parameters remained without significant changes. The placebo-group showed increments of AP, PTH, CT and 1.25–2OH-vitD.
Conclusions In pregnant women with low dietary Ca intake a parathyroid hyperfunction is present at least at the 20th week of pregnancy, a situation reverted by calcium supplement. In contrast to other studies IGF-1 did not show a systematic increase.
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