Recurrence of hyperparathyroidism; a long-term follow-up after surgery for primary hyperparathyroidism.

OBJECTIVE In general it is thought that recurrence of primary hyperparathyroidism is a rare event. To our knowledge, however, only one large patient series has been reported with a mean of more than 7 years of follow-up. The aim of the present study was to determine the long-term recurrence rate in 785 out of 886 patients operated on for primary hyperparathyroidism and followed-up for a mean of 10.03 years after surgery. DESIGN Medical records were scrutinised. The patients who were still alive answered a questionnaire and had laboratory tests. METHODS Follow-up data concerning the state of health, medical treatment, other diagnoses, renal function, and serum calcium and creatinine levels were found in the medical records of 203 patients, and were registered at the start of investigation of 582 patients. Intact parathyroid hormone values were determined in 252 patients. Recurrence rate and 95% confidence interval (C.I.) were calculated. RESULTS Recurrence rate of hyperparathyroidism with constant or intermittent hypercalcaemia (n=39) was 4.97% (95% C.I.=3.45-6.74%) during a mean of 10 years of follow-up. Nine out of 39 had elevated serum creatinine levels. Recurrence rate of hyperparathyroidism with normal serum creatinine levels, including patients with normocalcaemia, intermittent hypercalcaemia, and constant hypercalcaemia was estimated to be 7-8% during a mean of 10 years of follow-up. CONCLUSIONS Recurrence rate was determined with reasonable precision in this large patient series, and recurrence of hyperparathyroidism cannot be considered to be extremely rare, but it may occur more than 20 years after treatment in both single and multiple gland disease.