PTH and Hypocalcemia: The mean pre-RAI PTH and serum calcium levels in the normal serum calcium group were higher than those in the hypocalcemia group (4.30 ± 1.23 pmol/L vs. 3.74 ± 1.19 pmol/L, P = 0.03 and 2.28 ± 0.09 mmol/L vs. 2.19 ± 0.06 mmol/L, P < 0.001, respectively).