Prediction of Permanent Hypoparathyroidism after Total Thyroidectomy

BACKGROUND: Hypoparathyroidism is a common complication with thyroid surgery. The ability to predict a high risk of permanent hypoparathyroidism is important for individual prognosis and follow-up. METHODS: Permanent hypoparathyroidism, defined as continuing need for vitamin D medication at 1-year post-operatively, was investigated in patients after total thyroidectomy. Blood levels of calcium and parathyroid hormone (PTH) were measured intra-operatively, the day after surgery and at 1 month post-operatively. Logistic regression analysis was performed to investigate the risk of vitamin D treatment at last follow-up, calculated as odds ratios (ORs) with 95 % confidence intervals (CIs). Patients were followed until cessation of vitamin D and/or calcium medication, until death, loss to follow-up, or end of follow-up, whichever came first. RESULTS: A total of 519 patients were included. The median (range) follow-up in patients unable to cease vitamin D was 2.7 (1.2-10.3) years. The rate of permanent hypoparathyroidism was 10/519, 1.9 %. Parathyroid auto-transplantation was performed in 90/519 (17.3 %) patients. None of these developed permanent hypoparathyroidism, nor did any patient with normal PTH day 1 (>1.6 pmol/l or 15 pg/ml). The adjusted risk (OR, 95 % CI) for permanent hypoparathyroidism for log PTH on day 1 was 0.25 (0.13-0.50). In patients not auto-transplanted and with unmeasurable PTH day 1 (<0.7 pmol/l or 6.6 pg/ml), 8/42 (19.2 %) developed permanent hypoparathyroidism. CONCLUSIONS: Auto-transplantation protects against permanent hypoparathyroidism, whereas low PTH day 1 is associated with high risk.