Monitoring for hypocalcemia after thyroidectomy, using only symptoms and serum calcium
levels, can delay the discharge of patients who will remain normocalcemic and can
delay the treatment of hypocalcemic patients.
We conducted a systematic search for articles describing use of parathyroid hormone
(PTH) assay, checked within hours of completing thyroidectomy, to predict postoperative
symptomatic hypocalcemia. Studies were excluded if all patients were treated with
postoperative calcium, or if early PTH values were used to alter management of the
patient. Individual patient data (perioperative PTH and calcium levels, development
of hypocalcemia) were obtained for 457 patients from the corresponding authors of
9 studies and pooled to yield the following results.
PTH, checked at three time periods after removal of the thyroid gland (0 to 20 minutes,
1 to 2 hours, and 6 hours), was substantially lower in patients who became hypocalcemic
compared with those who remained normocalcemic. The accuracy of PTH in determining
hypocalcemia increased with time and was excellent when checked 1 to 6 hours postoperatively.
A single PTH threshold (65% decrease compared with preoperative level), checked 6
hours after completing thyroidectomy, had a sensitivity of 96.4% and specificity of
91.4% in detecting postoperative hypocalcemia.
PTH assay, when checked 1 to 6 hours after thyroidectomy, has excellent accuracy in
determining which patients will become symptomatically hypocalcemic. Routine use of
this assay should be considered because it may allow earlier discharge of the normocalcemic
patient and earlier identification of patients requiring treatment of postthyroidectomy
hypocalcemia.