Vitamin D status affects serum parathyroid hormone concentrations during winter in female adolescents: associations with forearm bone mineral density

Abstract

A large percentage of adolescent females have low vitamin D status during the winter in Finland, which seems to have negative effects on bone health.

Adverse interaction of low-calcium diet and low 25(OH)D levels on lumbar spine mineralization in late-pubertal girls

“…(46) One possible explanation would be that this adaptive mechanism, because it depends on 1,25-dihydroxyvitamin D 3 [1,25(OH) 2 The proposed threshold of 40 nmol/L for serum 25(OH)D levels to enable optimal lumbar spine mineralization during late puberty, even in low-calcium, low-dairy-product conditions, is similar to thresholds proposed earlier for optimal bone mass accrual during growth: 25 TO 30 nmol/L (9,10,13,35,36) or 40 to 50 nmol/L. (10,11) Given the small size of the subgroup with low calcium and low 25(OH)D levels, it was not possible to single out the negative impact of low 25(OH)D levels from that of other factors associated with winter-spring (eg, lower ultraviolet light energy, qualitative difference in sport activities, or diet). But low serum levels of 25(OH)D remain a good marker of the negative impact of these factors on the lumbar spine mineralization of adolescent girls with low calcium intake.…”

“…(9)(10) But the consequences of low 25(OH)D levels are less clear on trabecular bone sites, such as hip, upper femur, and lumbar spine. (8,9,12,13) At the lumbar spine, one longitudinal observational study (13) and two randomized, placebo-controlled studies (42,43) suggest that low 25(OH)D levels may impair bone mass acquisition during the early phase of puberty, but not in girls with more advanced sexual maturation.…”

“…(1)(2)(3)(4)(5)(6) But data on a possible impact of low vitamin D status are less convincing. (7,8) Indeed, associations between low 25-hydroxyvitamin D [25(OH)D] levels, below 25 to 30 nmol/L (9) or 40 to 45 nmol/L, (10,11) and impaired bone mineralization have been observed at appendicular sites (ie, tibia and forearm) in girls during growth but not at trabecular bone sites (eg, hip, femoral neck, or lumbar spine) (9,12,13) or only during the early phase of puberty in severely vitamin D-deficient girls with 25(OH)D levels below 20 nmol/L. (13) Serum 25(OH)D levels are considered the best marker of vitamin D status and have been used commonly to assess the prevalence of vitamin D deficiency/insufficiency in healthy children and adolescents.…”

“…(13) Serum 25(OH)D levels are considered the best marker of vitamin D status and have been used commonly to assess the prevalence of vitamin D deficiency/insufficiency in healthy children and adolescents. (9,10,(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26) However, a clear understanding of the biologic significance of given concentrations of circulating 25(OH)D is still lacking, and reference ranges for vitamin D are being reassessed on the basis of what constitutes a normal concentration compared with optimal concentrations. (27)(28)(29) Most clinicians agree that serum 25(OH)D levels below 25 to 30 nmol/L (10 to 12 ng/mL) may lead to nutritional rickets, hypocalcemic convulsions, dental problems, and poor growth in children and adolescents.…”

“…(27)(28)(29) Most clinicians agree that serum 25(OH)D levels below 25 to 30 nmol/L (10 to 12 ng/mL) may lead to nutritional rickets, hypocalcemic convulsions, dental problems, and poor growth in children and adolescents. (30)(31)(32)(33)(34)(35)(36) But the lower threshold of optimal vitamin D status for bone health and calcium homeostasis during growth is still under discussion, with cutoff values proposed from 25 to 30 to 70 to 90 nmol/L in children, (9,10,23,36) as in adults. (12) Differences in the 25(OH)D assays used might explain some discrepancies, especially because results have not been validated systematically using external control assessment schemes.…”