Post-thyroidectomy hypocalcaemia is common and drives longer stays and unplanned hospitalisation. Vitamin D deficiency may worsen hypocalcaemia, but preoperative testing and replacement are not yet routine in many centres. We aim to evaluate practice patterns in our centre on preoperative vitamin D testing and replacement among patients planned for total or completion thyroidectomy, as well as associated rates of post-thyroidectomy hypocalcemia and its effect.

We designed a retrospective cohort study of adult patients undergoing total or completion thyroidectomy at Sengkang General Hospital, Singapore, from January 2020 to December 2024. Approximately 120 cases were performed during this period. For each case, we identify whether a preoperative 25-hydroxyvitamin D [25(OH)D] level was checked and classify patients as: (i) no vitamin D test; (ii) vitamin D normal; (iii) vitamin D low without preoperative replacement; or (iv) vitamin D low with preoperative replacement based on in-house laboratory reference ranges. Post-operative biochemical and symptomatic hypocalcaemia, use of intravenous calcium, oral calcium/active vitamin D at discharge, length of stay and 30-day hypocalcaemia-related readmission were evaluated. Outcomes were compared across groups using appropriate univariable tests and exploratory multivariable models adjusting for key clinical covariates.

Preliminary data suggest that preoperative vitamin D testing is performed in a minority of thyroidectomy patients (<25%). Transient hypocalcemia was seen in 30% of this cohort. Among them, 40% had vitamin D deficiency, 10% has normal preoperative Vitamin D level, while 50% did not have preoperative Vitamin D documented. No permanent hypocalcemia was noted in our series.

This single-centre cohort informs how often preoperative vitamin D is assessed and corrected before thyroidectomy and suggests that vitamin D status and replacement could alter post-operative incidence of hypocalcemia, duration of medication use and hospitalisation. A protocol to include Vitamin D assessment and optimisation pre-operatively should be incorporated into the thyroidectomy clinical pathway.