The cut−off point of serum 25− OHD in which the mean serum PTH concentration begins to increase is defined as 20 or 30 ng/ml.(9, 13, 15, 22, 27, 28, 29) When we used a cut−off point of 20 ng/ml and even a cut−off level 10 ng/ml, we were not able to demonstrate secondary hyperparathyroidism, nor a correlation between serum 25−OHD and ALP and iPTH levels. The gene discussed is PTH; the disease is secondary hyperparathyroidism.