PTH and Hypocalcemia: The range of responses in our group is shifted to the left compared to the initial results reported by Iwasaki et al. It is a matter of discussion and further investigation to clarify whether our observations are, at least partly, produced due to the presence of individuals with a constitutively blunted response of PTH or if low levels of vitamin D decrease the ability of the parathyroid glands to respond to a potent stimulus such as acute hypocalcemia.