Figure 1From: Prevalence of hypovitaminosis D and predictors of vitamin D status in Italian healthy adolescents Individual PTH levels according to serum 25-OH-D values. Circles over the horizontal line (65.0Â ng/L) are subjects with secondary hyperparathyroidism. Vertical lines represent the 25-OH-D cut-off of 25, 50 and 75Â nmol/L.Back to article page