Prevalence and Factors Associated With Hypoparathyroidism After Total Thyroidectomy for Thyroid Cancer: A French Nationwide Claims Database Study

OBJECTIVES: Hypoparathyroidism is the most common complication of total thyroidectomy for thyroid cancer. The resulting hypocalcemia may be transient or permanent and require calcium and/or vitamin D supplementation. Our aim was to assess the prevalence of the postoperative hypoparathyroidism in France and explore the factors associated with its occurrence.

METHODS: Adult patients who underwent a total or completion thyroidectomy for cancer between 2011 and 2015 were identified in the French national cancer cohort, including all cancer patients diagnosed since 2010 and based on the large French health insurance claims database (SNDS).

Hypoparathyroidism was defined by initiation of calcium and/or vitamin D supplementation within the first postoperative month and/or hospitalization for severe hypocalcemia at any time in the first postoperative year. Factors associated with hypoparathyroidism were investigated with a stepwise logistic regression model.

RESULTS: Of the 31,175 included patients, 13,247 (42%) were considered as having hypoparathyroidism. Among the 13,224 patients treated with calcium/vitamin D, 2,855 (22%) had a permanent hypoparathyroidism with treatment continued at 1 year.

As expected, probability of hypoparathyroidism was higher in patients with longer surgery stay (OR: 1.011, 95%CI: 1.002-1.020 by supplementary day) or lymph node dissection (central: OR: 1.651, 95%CI: 1.548-1.761; lateral: OR: 1.743, 95%CI: 1.627-1.866 compared to no dissection) and lower in patients with completion thyroidectomy (OR: 0.507, 95%CI: 0.467-0.550).

Gender (OR:0.630, 95%CI: 0.594-0.668 males compared to females), age (OR: 0.877, 95%CI: 0.818-0.939; OR: 0.738, 95%CI: 0.687-0.792; OR: 0.638, 95%CI: 0.593-0.686 from 2^nd to 4^th quartile compared to 1^st quartile) and low economic status (OR: 0.849, 95%CI: 0.780-0.923) were associated with a reduced hypoparathyroidism risk.

CONCLUSIONS: The prevalence of hypoparathyroidism after thyroidectomy for cancer was assessed on a large-scale study. The impact of factors related to the surgery on the risk of hypoparathyroidism was confirmed in our study. Hypoparathyroidism risk also seems to depend on patient-related characteristics.