Pregnancy-Related Change in pQCT and Bone Biochemistry in a Population With a Habitually Low Calcium Intake.

In pregnancy, changes in maternal calcium (Ca) economy occur to satisfy fetal Ca demand. It is unclear whether maternal mineral reserves facilitate these requirements and no data exist from sub-Saharan Africa. The aim was to determine skeletal changes with peripheral quantitative computed tomography (pQCT) and bone biochemistry between early second and third trimesters. Pregnant rural Gambians aged 18 to 45 years (n = 467) participating in a trial of antenatal nutritional supplements (ISRCTN49285450) had pQCT scans and blood collections at mean (SD) 14 (3) and 31 (1) weeks' gestation. Outcomes were pQCT: radius/tibia 4% total volumetric bone mineral density (vBMD), trabecular vBMD, total cross-sectional area (CSA), 33%/38% radius/tibia cortical vBMD, bone mineral content (BMC), total CSA; biochemistry: collagen type 1 cross-linked ß-C-telopeptide (ß-CTX), type 1 procollagen N-terminal (P1NP), parathyroid hormone (PTH), and 1,25(OH)2 D. Independent t tests tested whether pooled or within-group changes differed from 0. Multiple regression was performed adjusting for age. Data for change are expressed as mean (confidence interval [CI] 2.5, 97.5%). Radius trabecular vBMD, cortical vBMD, and BMC increased by 1.15 (0.55, 1.75)%, 0.41 (0.24, 0.58)%, and 0.47 (0.25, 0.69)%. Tibia total and trabecular vBMD increased by 0.34 (0.15, 0.54)% and 0.46 (0.17, 0.74)%, while tibia cortical vBMD, BMC, and cortical CSA increased by 0.35 (0.26, 0.44)%, 0.55 (0.41, 0.68)% and 0.20 (0.09, 0.31)%, respectively. CTX, PTH, and 1,25(OH)2 D increased by 23.0 (15.09, 29.29)%, 13.2 (8.44, 19.34)%, and 21.0 (17.67, 24.29)%, while P1NP decreased by 32.4 (-37.19, -28.17)%. No evidence of mobilization was observed in the peripheral skeleton. Resorption, although higher in late versus early gestation, was lower throughout pregnancy compared with non-pregnant non-lactating (NPNL) in the same community. Formation was lower in late pregnancy than in early, and below NPNL levels. This suggests a shift in the ratio of resorption to formation. Despite some evidence of change in bone metabolism, in this population, with habitually low Ca intakes, the peripheral skeleton was not mobilized as a Ca source for the fetus. © 2021 crown copyright . Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR). The article published with the permission of the Controller of HMSO and the Queen's Printer of Scotland..

Birth weight predicts bone size in young adulthood at cortical sites in men and trabecular sites in women from The Gambia.

Fracture risk is determined by bone mass, size and architecture. Birth weight (Bwt) is reported to predict adult bone mass and density. Early life environment may therefore be a determinant of bone strength in later life. However such evidence was obtained using dual energy X-ray absorptiometry (DXA), which is known to be dependent on size. We used peripheral quantitative computed tomography (pQCT) and DXA to investigate Bwt as a determinant of bone size and cross section area (CSA), bone mineral content (BMC) and volumetric bone mineral density (vBMD) and areal BMD (aBMD) independent of current weight, height and age. The study population consisted of 68 males and 52 nulliparous females aged 17 to 21years from Keneba, The Gambia. This population has a high prevalence of factors likely to influence skeletal development (poor nutrition, low calcium intake, late puberty and high physical activity). Measures of bone size and CSA, BMC and BMD were obtained using pQCT (Stratec 2000; at 4% and 66% radius; 4% and 50% tibia) and DXA (Lunar DPX; spine, hip, forearm and whole body). Sequential univariable (influence of Bwt on bone variables) and multivariable linear regression analyses (influence of Bwt on bone variables after adjusting for current height, weight and age) were used to investigate the independent effects of Bwt and attained size. Analyses were performed separately by sex. Bwt was a significant positive predictor of CSA at appendicular cortical sites in males and CSA and bone area at appendicular and most axial trabecular sites in females before and after adjustment for current height, weight and age. Bwt was not consistently related to BMC, vBMD or aBMD as measured by pQCT or DXA. Current weight was a positive predictor of aBMD and pQCT- and DXA-derived BMC in males and females. Height predicted aBMD and trabecular vBMD in males. In summary, Bwt significantly predicted attained CSA at cortical sites in males and at trabecular sites in females. Current weight was a positive predictor of BMC and aBMD in both sexes. This suggests that pre-natal factors affecting fetal growth may influence adult bone strength independently of post-natal factors.

FGF23 is elevated in Gambian children with rickets.

OBJECTIVES: Fibroblast growth factor 23 (FGF23) is a phosphaturic factor that is elevated in several diseases associated with hypophosphatemia and rickets. Rickets in the absence of vitamin D deficiency has been reported in African and Asian populations with a low calcium intake but the definition of risk factors has proved elusive. The aim of the study was to characterize the biochemical profile and measure FGF23 in a series of Gambian children who had presented with rickets of unknown etiology and a plasma 25-hydroxyvitamin D (25OHD) above the range typical of vitamin D-deficiency rickets. METHODS: The 46 patients (30 males, 16 females) had bone deformities typical of rickets and were 1.1-16.4 years old (geometric mean, 3.4 years). Active rickets (on radiographs and/or elevated plasma alkaline phosphatase) was present in 28%. Plasma 25-hydroxyvitamin D was above 20 nmol/l in all patients. Concentrations of plasma FGF23, phosphate and other relevant biochemical analytes were measured in stored samples of fasting, early morning plasma and compared with those measured in samples collected from local children and stored under similar conditions. RESULTS: The rickets patients had lower plasma phosphate, lower 25-hydroxyvitamin D, higher 1,25-dihydroxyvitamin D and elevated total alkaline phosphatase than local children. Those with active rickets had raised parathyroid hormone concentration. The patients had significantly higher FGF23 concentration than local children (geometric mean (-1SD, +1SD, range) RU/ml: 367 (87, 1552, 46-7052, n=39) vs 51 (23, 112, 3-130, n=30), p

Bone mineral contents and plasma osteocalcin concentrations of Gambian children 12 and 24 mo after the withdrawal of a calcium supplement.

BACKGROUND: Our randomized, placebo-controlled supplementation study of 160 rural Gambian children aged 8.3-11.9 y showed that an increase in calcium intake of 714 mg/d for 12 mo resulted in a 5% increase in forearm bone mineral acquisition and a 22% decrease in plasma osteocalcin concentration, a bone formation marker, but had no effect on height or bone dimensions. OBJECTIVE: We investigated whether these results were sustained after supplement withdrawal. DESIGN: All participants were followed up 12 (FU1) and 24 (FU2) mo after supplementation ended. Bone mineral content (BMC), bone mineral density (BMD), and BMC adjusted for bone width, body weight, and height (size-adjusted BMC) were measured at the midshaft and distal radius. Plasma osteocalcin concentration was measured at FU1. RESULTS: At follow-up, the calcium group had greater bone mineral status than did the placebo group at the midshaft radius (mean difference +/- SE), FU1: BMC (4.7 +/- 1.6%; P = 0.004), BMD (5.1 +/- 1.1%; P