Circulating intact parathyroid hormone is suppressed at 25-hydroxyvitamin D concentrations >25 nmol/L in children.

Vitamin D status is best reflected by circulating concentrations of 25-hydroxyvitamin D2 and D3 (25-OH-D). An adequate blood concentration of total 25-OH-D is commonly defined as that which maintains parathyroid hormone (PTH) within the normal range. Consensus from studies of adults with renal impairment indicates that 75 nmol/L of 25-OH-D maintains suppression of PTH. No similar consensus exists in children. We studied the correlation of PTH and 25-OH-D in 271 patients aged 2 months to 21 years (mean 11 years) in a tertiary care pediatric setting. Patients with renal impairment were excluded by elevated creatinine concentration and chart review. PTH did not significantly correlate with 25-OH-D concentrations >25 nmol/L. PTH was significantly elevated in specimens with <25 nmol/L of 25-OH-D (p=10-17). Using PTH suppression as indicator, these data suggest that 25-OH-D concentrations >25 nmol/L in children indicate vitamin D sufficiency.