Early Prediction of Oral Calcium and Vitamin D Requirements in Post-thyroidectomy Hypocalcemia

Abstract

Objectives:

Optimize and individualize post-thyroidectomy hypocalcemia management.

Methods:

A multicenter, standardized prospective study was conducted. Demographic, clinical, and biochemical data were collected. Parathyroid hormone (PTH) was measured preoperatively, then at 1 and 6 hours postoperatively. The optimal required doses of calcium and vitamin D were defined as those maintaining the patients as asymptomatic and their cCa ≥ 2 mmol/L. They were used as an endpoint in a generalized linear mixed effect modeling (GLIMMIX) aiming to identify the best predictors of optimal required doses. Models were evaluated by goodness of fit (Akaike information criteria), receiver operating characteristic curves, and sensitivity analysis.

Results:

A total of 168 patients met inclusion criteria; mean age was 41.8 years, 85.1% were female, 49.3% had a body mass index (BMI) >30, and 64% had vitamin D deficiency. Of the patients, 25.6% had post-thyroidectomy hypocalcemia, of whom 18 (41.9%) were symptomatic and received intravenous calcium. First-hour percentage drop in PTH correlated positively with the severity of hypocalcemia (P < .0001). The GLIMMIX prediction model for oral calcium requirement was based on first-hour percentage change from preoperative PTH level, preoperative actual PTH, BMI, and thyroid function. The same predictors were identified for vitamin D, except that thyroid function was replaced with vitamin D status. These factors were used to build predictive equations for calcium and vitamin D doses.

Conclusions:

Our findings could help in optimizing the management of post-thyroidectomy hypocalcemia. They can assist in early identification of those who are not at risk of hypocalaemia and can guide early effective management of those at risk.