Parathyroid hormone of ≥1.6 pmol/L at 6 months is associated with recovery in 'long-term' post-surgical hypoparathyroidism.

Objective: Post-surgical hypoparathyroidism (PoSH) usually settles within few months after thyroid surgery, but several patients require long-term supplementation with calcium/activated vitamin D. When PoSH persists beyond 6 months, it is considered 'chronic' or 'permanent', however, late recovery has been reported. The aim of this study was to determine the frequency of late recovery and explore factors predicting late recovery of parathyroid function. Methods: Adult patients undergoing total/completion thyroidectomy between 2009 and 2018 were included in this retrospective cohort observational study. The records of patients with evidence of PoSH were reviewed to identify those with persisting PoSH at 6 months. Demographic, biochemical, surgical, pathological, and clinical follow-up data were collected and analysed. Results: Out of 911 patients undergoing thyroidectomy, 270 were identified with PoSH. Of these, 192 were started on supplements and 138 (71.9%) recovered within 6 months. Of the remaining 54 patients, 35 had ongoing PoSH with median (range) follow-up of 3.4 (0.5-11.1) years. Nineteen patients were weaned off supplements and achieved remission at median (range) follow-up of 1.3 (0.6-4.8) years. All of those who recovered had a PTH of ≥1.6 pmol/L at 6 months. There was no difference in age, gender, diagnosis, type, and extent of surgery between those who did and did not show late recovery. Conclusions: Recovery from PoSH is common beyond 6 months, raising the question whether a 6-month threshold to define 'long-term' PoSH is appropriate. The chances of recovery are high (~50%) in patients with PTH level ≥1.6 pmol/L at 6 months, where attempts at weaning may be focussed.