The impact of baseline intact parathyroid hormone levels on severity of primary hyperparathyroidism and outcomes in patients undergoing surgery

Objective: To determine the impact of intact parathyroid hormone (iPTH) baseline levels on severity of primary hyperparathyroidism (PHPT) and outcomes following parathyroidectomy for PHPT. Design: Single institution retrospective review. Setting: Academic tertiary care center. Patients: A total of 447 consecutive patients undergoing parathyroid surgery for PHPT. Main Outcome Measures: Comparison of patients with high (≥150 pg/mL) and low (<150 pg/mL) baseline iPTH values; preoperative serum calcium, alkaline phosphatase, and 25-hydroxyvitamin D levels; and 6-month postoperative serum calcium and iPTH levels. Results: A total of 304 patients had baseline iPTH values of at least 150 pg/mL (high baseline group), and 143 patients had baseline iPTH values lower than 150 pg/mL (low baseline group). Patients in the high baseline group had significantly higher levels of preoperative serum calcium, serum alkaline phosphatase, and adenoma weights (P<.001 for all comparisons). Serum 25-hydroxyvitamin D levels were significantly lower in patients in the high baseline group (P<.001). Sestamibi scans were more likely to localize an adenoma in the high baseline group (83.7%) than in the low baseline group (68.9%) (P<.01). There were no differences in the serum calcium and iPTH levels between the 2 groups 6 months after surgery. Conclusions: Patients in the high baseline group undergoing surgery for PHPT had higher baseline levels of serum calcium, serum alkaline phosphatase, and parathyroid adenoma weights and lower serum 25-hydroxyvitamin D levels compared with the lower baseline group. Sestamibi scans were more likely to localize an adenoma in the high baseline group (83.7%) than in the low baseline group (68.9%) (P<.01). Despite an apparently lower rate of positive preoperative sestamibi scans for the low baseline group, patients were able to achieve a similar rate of disease cure as other patients with higher baseline iPTH levels. It seems that baseline iPTH level should not be used as a criterion to perform surgery or not perform surgery for patients with PHPT.