Longitudinal Lactation Bone Density Study
Changes in maternal calcium metabolism are necessary during lactation to provide adequate calcium in breast milk for development of the newborn skeleton. The calcium in milk is derived from the maternal skeleton, resulting in significant bone loss, a process thought to be mediated by the actions of parathyroid hormone-related protein (PTHrP) in combination with a decreased estrogen levels. After weaning, bone lost during lactation is rapidly regained.
Differences between African-American and Caucasian bone metabolism are well documented and include higher bone mineral density (BMD), lower risk of fragility fracture, lower 25-hydroxyvitamin D (25(OH) D), and higher PTH in African-Americans compared to Caucasians. Most studies of bone metabolism in lactating women have been done in Caucasians. Because of differences in bone metabolism between African-Americans and Caucasians, we do not know whether African-Americans will have similar findings.
The primary aim of this study is to compare the changes in bone mineral density (BMD) during lactation in African-Americans with those in Caucasians. It is not known whether the loss in BMD during lactation will be the same for both races. African-Americans display skeletal resistance to PTH with short-term infusions and have lower bone resorption, higher BMD and lower fracture risk than Caucasians. A recent study by our group indicated that lactating African-American mothers had slightly lower bone resorption but quantitatively similar bone formation compared to Caucasians. However, there was a significant increase of 2-3 fold in markers of bone formation and resorption in both groups. Therefore, it is currently not known whether the loss in BMD during lactation will be the same for both races. Primary outcome measures in this study will include spine, hip and radius BMD by Dual X-Ray Absorbiometry (DXA)Scans during lactation (at 2,12 and 24 weeks postpartum or at weaning if prior to 24 weeks postpartum, and six months after weaning (+1 week). This longitudinal protocol will distinguish between two hypotheses. Either: a) as measured by BMD, bone loss in African-Americans during lactation will be equal to that in Caucasians, and skeletal recovery will be the same or possibly accelerated compared to Caucasians; or, b) African-Americans will be resistant to bone loss during lactation compared to Caucasians because of resistance to Parathyroid Hormone-related Protein (PTHrP).
Other Disorders of Bone Density and Structure
|Study Design:||Observational Model: Cohort
Time Perspective: Prospective
|Official Title:||"Bone Density and Calcitropic Hormones During Lactation in African-American and Caucasian Women"|
- Change from baseline in bone density measurements (BMD) [ Time Frame: Change from baseline in BMD at 2,12, 24 weeks postpartum, and six months after weaning. ]Primary outcome measures will include spine, hip and radius BMD by DXA at 2, 12, and 24 weeks post-partum and 6 months post-weaning.
- Change from baseline of bone metabolism measurements [ Time Frame: Change from baseline at 2, 12,and 24 weeks postpartum, and six months after weaning. ]Bone metabolism measurements include: markers of bone turnover including calcium metabolic parameters such as calcium, phosphorus, fractional excretion of calcium, PTH(1-84), PTHrP, vitamin D metabolites, estradiol, sex hormone binding globulin (SHBG), prolactin, and breast milk calcium levels.
Biospecimen Retention: Samples Without DNA
|Study Start Date:||August 2012|
|Study Completion Date:||September 2015|
|Primary Completion Date:||September 2015 (Final data collection date for primary outcome measure)|
African-American Lactating Women
Healthy African-American women who are exclusively breast-feeding.
Caucasian Lactating Women
Healthy Caucasian women who are exclusively breast-feeding.
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Please refer to this study by its ClinicalTrials.gov identifier: NCT01630629
|United States, Pennsylvania|
|University of Pittsburgh Medical Center|
|Pittsburgh, Pennsylvania, United States, 15213|
|Principal Investigator:||Mara Horwitz||University of Pittsburgh|