Not how much bone an adult has lost, but how it is built in the first place. Two studies of children's bone development found the skeleton is not one trait — different sites have different genetics — and one study found a gene that trades off muscle against bone at the exact same locus.
Solid lines are connections this site curates. Dashed lines mean the two ends share a research paper — worth knowing, and not a claim that one explains the other.
Adult bone density research, including this site's own heel bone mineral density page, mostly asks how much bone a person has left. Paediatric bone mineral density research asks a different question: how bone mass is built during childhood and adolescence, the years that set the ceiling for lifetime skeletal health.
Kemp et al. 2014 studied roughly 4,890 children in the ALSPAC cohort, using total-body DXA scans split by skeletal site rather than treated as one number. The genetic correlation between the two limb sites — upper and lower — was 0.78, substantially higher than the correlation between either limb and the skull (0.58 and 0.43). In plain terms: bone density in your arm and bone density in your leg are shaped by largely the same genes; bone density in your skull is shaped by a meaningfully different set. Splitting the skeleton apart this way, rather than averaging it into a single trait, is what let the study find loci a combined analysis would have missed. Six of this page's variants come from here, including two separate hits in WNT4 and two in FAM3C at different skeletal sites.
Medina-Gomez et al. 2017 studied 10,414 children, this time analysing bone density and lean (muscle) mass together rather than separately. Both traits were substantially heritable — 43% for bone density, 39% for lean mass — and shared 43% of that heritability in common. The study confirmed seven already-established bone density loci, including rs3765350 in WNT4, but its most striking single finding was a locus at TOM1L2/SREBF1 with opposing effects: the same variant that increases lean mass decreases bone density, and vice versa. That is a genuine biological trade-off at one genetic position, not two separate findings that happen to share a page.
Children's bone health is assessed by a paediatrician or specialist using growth charts, DXA scans where indicated, and clinical judgement — not by genotype. None of the ten variants on this page changes how a child's bone development is monitored or managed.
The genuinely useful idea here is conceptual rather than actionable: bone and muscle mass are not independent systems that happen to sit near each other in the body. The TOM1L2/SREBF1 finding shows a single genetic position can push them in opposite directions at once, which is a real biological constraint worth knowing about — not a reason to test a child's genotype before deciding anything about their diet, activity, or growth monitoring, all of which remain unchanged by any finding here.
What a 23andMe/AncestryDNA export or raw VCF can and can't tell you about Paediatric Bone Mineral Density comes down to these specific, well-studied positions — not a diagnosis.
CPED1 · rs2110281
See detailed info →WNT4 · rs3765350
See detailed info →near GALNT3 · rs6726821
See detailed info →PPP6R3 · rs12283755
See detailed info →TNFSF11 · rs17536328
See detailed info →FAM3C · rs7776725
See detailed info →The studies behind these variants recruited participants from different ancestries — a result found in one population doesn't always transfer to another. Based on 16 of 16 linked studies with a resolved discovery ancestry.
Databases, guidelines and references
No. Children's bone health is assessed with growth charts, clinical judgement, and DXA scans where indicated — not genotype. These variants come from population studies and are not diagnostic.
Related but distinct. This page is about how bone mass is built during growth; this site's heel bone mineral density and osteoporosis pages are about adult bone density and fracture risk. They share some of the same genes but ask different questions.
Medina-Gomez et al. 2017 found a locus at TOM1L2/SREBF1 with opposing effects on the two traits — the same variant that increases lean (muscle) mass decreases bone density, and vice versa. That is a real trade-off at one genetic position, not a coincidence of two unrelated findings.
Kemp et al. 2014 found the genetic correlation between limb sites (0.78) was notably higher than between either limb and the skull (0.58 and 0.43) — evidence that different bones are shaped by partly different genetic programs, not simply one skeleton-wide trait.
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