Causes of hypocalcemia after thyroid surgery

Aim. To identify the causes affecting hypocalcemia and its frequency of causing after thyroidectomy.

Methods. The study included 402 patients after thyroidectomy, 361 (89.8%) women and 41 (10.2%) men, for the period 2015–2019. The patients were between the ages of 14 and 77 years (average 45±27.2 years). Patients were tested for the presence of hyperthyroidism, the volume of tissue removed and type of thyroidectomy, presence of repeated thyroid operations and accidental parathyroidectomy, the results of parathyroid autotransplantation and pathohistological reports. To determine the effect of these factors on hypocalcemia, patients were divided into three groups. The first group included patients (n=51, 12.7%) were underwent surgery for Graves’ disease, the second (n=335, 83.3%) — for nodular goiter, and the third (n=16, 4%) — for recurrent goiter. Statistical data analysis was performed with IBM SPSS 16.0. The results were analyzed by one-way analysis of variance or Kruskal–Wallis test and the median test. Results were considered statistically significant at p <0.05 (two-sided criterion).

Results. In the early postoperative period, 20 (5%) of 402 patients had hypocalcemia, of which 12 (3%) had transient hypocalcemia, and 8 (2%) had permanent hypocalcemia. Postoperative hypocalcemia was detected in 9 (17.6%) patients the first group, 8 (2.4%) patients — in the second group, and 3 (18.8%) patients of the third group. Patients’ hypocalcemia was characterized based on the types of underwent operations as follows: in 14 (5.3%; p <0.05) patients after total thyroidectomy, in 1 (3.2%) patient after close to total thyroidectomy, in 1 (16.7%) patient after total thyroidectomy with central lymphatic dissection, in 1 (20%) patient after total thyroidectomy with central and lateral lymphatic dissection, in 3 (18.8%) patients after repeated surgery. Postoperative hypocalcemia was identified in 5 of 44 patients of the second group with thyroid carcinoma, as well as in 1 patient of the third group with the same pathology (p=0.246).

Conclusion. Incidence of hypocalcemia was more frequent after surgery for hyperthyroidism, especially after total thyroidectomy; in 40% of cases, transient hypocalcemia was identified in patients with autotransplantation of the parathyroid gland after an accidental parathyroidectomy.