Early (1 hour) post-operative parathyroid hormone (PTH) measurement predicts hypocalcaemia after thyroidectomy: a prospective case-control single-institution study

The aim of the study was to evaluate the efficacy of parathyroid hormone 1-hour assay for the early prediction of hypoparathyroidism after thyroidectomy. Candidates for total, subtotal, completion thyroidectomy or lobectomy were entered into the study. Pre- and postoperative calcium and parathyroid hormone (1 hour and postoperative day 1 after thyroidectomy) levels and clinical hypocalcaemia were recorded. Patients were divided into 3 groups and 2 subgroups: 1. patients who underwent lobectomy (control group); 2. patients who underwent total thyroidectomy with postoperative hypocalcaemia (2A: asymptomatic patients, 2B: symptomatic patients); 3. asymptomatic patients with normal calcium levels after total thyroidectomy. Of 119 patients, 109 underwent total thyroidectomy and 10 lobectomy. Of the 109 patients submitted to total thyroidectomy, 35 (32.11%) developed postoperative transient hypocalcaemia. Twenty-one patients (19.27%) were asymptomatic and 14 (12.84%) were symptomatic. Parathyroid hormone levels decreased after 1 hour in group 3 (32.98 pg/dl), 2A (9.84 pg/dl) and 2B (7.46 pg/dl). There was no significant difference in parathyroid hormone levels at 1 hour between group 2A and 2B (p = 0.06), but were significantly lower compared to groups 3 and 1 (p < 0.05). Parathyroid hormone levels at 1 hour after total thyroidectomy is a good predictor of early hypocalcaemia. It might be more useful than serum calcium monitoring for the early identification of patients requiring postoperative calcium supplementation.