Objective: To describe the course of parathyroid hormone (PTH) and serum calcium after surgery for primary hyperparathyroidism and to evaluate the usefulness of daily measurement of these parameters.

Design: Prospective clinical study.

Setting: University hospital K. U. Leuven.

Method: Daily monitoring of PTH and serum calcium (preoperatively, the first to the 5th postoperative day, and around the 10th day) in 30 patients where a parathyroid adenoma was removed and in 1 patient with a negative neck exploration.

Results: In the adenoma cases, PTH and serum calcium showed a sharp drop of PTH to a very low level already on the first postoperative day, whereafter a rapid recovery of the PTH was seen. Serum calcium decreased more slowly: on average, the lowest calcium level was measured on the third day, when a majority of the patients were temporarily hypocalcemic; after 2 weeks, only four patients remained slightly hypocalcemic and no one showed recurrence of the hypercalcemia. In contrast, after unsuccessful surgery (biopsy of four normal glands), the PTH decrease on the first day was far less pronounced and the hypercalcemia disappeared only for a short time.

Conclusions: After removal of a parathyroid adenoma, an abrupt fall of PTH precedes the decrease of serum calcium. The first day's PTH level is a reliable indicator of the success of the intervention, and it should be a major point in the postoperative biochemical follow-up. Repeated measurements of serum calcium are useful, but the daily dosage of PTH might be omitted for economic reasons.