Permanent hypothyroidism was defined as persistently low PTH (less than 12 pg/mL), low serum calcium (less than 8.0 mg/dL), and/or requiring calcitriol to maintain a normal calcium level for more than 6 months after total thyroidectomy.
Those with both low calcium and PTH levels were 4.3 times more likely to develop permanent hypoparathyroidism than those in the other groups, according to Dr. Brown.
Patients in the permanent hypoparathyroid group had a PTH drop of 70%, compared with 39% in the nonhypoparathyroid group. There was also a significant difference in respective drops of calcium levels (17.8% vs. 14.3%).