The prevalence rate of a blunted PTH response was almost 20%, which was lower than that reported in other studies [16, 18–20], most of which defined vitamin D deficiency as a 25(OH)D level <50 nmol/L which is higher than the cutoff value used in this study (<30 nmol/L), and hence, the probability of a normal PTH level was higher. Here, PTH is linked to vitamin D deficiency.