BONE METABOLISM AFTER HUMAN PARTURITION AND THE EFFECT OF LACTATION -LONGITUDINAL ANALYSIS OF SERUM BONE-RELATED PROTEINS AND BONE-MINERALCONTENT OF THE LUMBAR SPINE

A prospective study was performed to investigate postpartum changes in human bone metabolism and the effects of lactation on them. The subje cts consisted of two groups: 13 women who stopped breast-feeding withi n 3 months postpartum (short-term group) and 14 women who continued br east-feeding for more than 6 months postpartum (long-term group). Seru m carboxyl-terminal propeptide of type I procollagen (PICP), carboxyl terminal cross-linked telopeptide of type I collagen (ICTP), and bone gla protein (BGP) were measured prepartum, and at 5 days, 1 month, 3 m onths and 9 months postpartum. Lumbar BMD was measured at 3-7 days, 3 months and 9 months postpartum. Between prepartum and 3 months postpar tum, the values and variations in the markets were essentially the sam e in both groups. PICP was maintained at a constant and significantly higher level than the control value. In contrast, ICTP had increased m arkedly at 5 days postpartum, gradually decreasing thereafter. BGP was low prepartum and gradually increased. At 9 months postpartum, PICP a nd ICTP decreased to the control values in the short-term group. The p ostpartum time course of lumbar BMD showed a significant decrease in b oth groups at 3 months postpartum. Recovery to the puerperal level was seen at 9 months postpartum in the short-term group but not in the lo ng-term group. In conclusion, bone resorption is stimulated by parturi tion as well as lactation resulting in postpartum loss of lumbar BMD.