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Featured Publication in Focus: Bone Metabolism & PTH

Featured Publication in Focus: Bone Metabolism & PTH Vitamin D status and parathyroid hormone relationship in adolescents and its association with bone health parameters: analysis of the Northern Ireland Young Heart’s Project

T R Hill, A A Cotter, S Mitchell, C A Boreham, W Dubitzky, L Murray, J J Strain, A Flynn, P J Robson, J M W Wallace, M Kiely, K D Cashman

Osteoporos Int 21, 695–700 (2010)

It is recognized that severe hypovitaminosis D (defined by a serum 25-hydroxyvitamin D (25(OH)D) concentration <25 nmol/l) causes rickets in children and osteomalacia in adults [1]. In contrast, the effects of less severe forms of hypovitaminosis D (serum 25(OH)D concentrations between 25 and 50 nmol/l) on the skeleton are less well understood [24]. It is well established that there is an inverse relationship between low 25(OH)D concentrations and parathyroid hormone (PTH), which can increase the rate of bone turnover and promote loss of bone mineral [5]. Indeed, while a number of criteria can be considered, the serum 25(OH)D value at which PTH plateaus (referred to as the point of inflection) is considered by many as the most appropriate criterion for defining adequate vitamin D status in adults [57].Elevations in PTH concentrations may not be driven by the same mechanism in adolescents as in adults and may not necessarily be detrimental to bone health. For example, serum PTH concentrations are normally raised during adolescence [8,9] when the rate of bone remodeling and consolidation is at a peak. Thus, the appropriateness of defining vitamin D adequacy on the basis of suppression of PTH in children and adolescents is not established. Notwithstanding this issue, an inverse relationship between serum 25(OH)D and PTH during adolescence had been shown in a number of studies (for review, see [10]) but with variable points of inflection between 25 and 93 nmol/l. Furthermore, three of these studies (in adolescent girls) provide evidence for a possible adverse effect on bone mineral acquisition and bone remodeling in adolescents with serum 25(OH)D levels below such cutoffs [10].

To our knowledge, no study exists that has investigated the association between 25(OH)D and PTH in a large representative sample of young adolescent boys and girls. Therefore, the objective of the present study was to determine whether a point of inflection exists for adolescent girls and boys from a large representative sample of young adolescents and furthermore to investigate whether this threshold in serum 25(OH)D concentrations might differentiate between measures associated with beneficial or adverse effects on bone health.

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https://doi.org/10.1007/s00198-009-0959-1