Biochemical and Skeletal Outcomes of Parathyroidectomy for Normocalcemic (Incipient) Primary Hyperparathyroidism

Background: Normocalcemic (incipient) primary hyperparathyroidism (PHPT) is characterized by inappropriately elevated parathyroid hormone (PTH) levels in the setting of normal serum calcium. The biochemical and skeletal outcomes after parathyroidectomy for normocalcemic PHPT are not well-described.

Methods: All patients who underwent parathyroidectomy for normocalcemic PHPT at a single institution were retrospectively reviewed (2006-2016). Pre- and postoperative calcium, PTH, and bone mineral density (BMD) were compared between patients with normalized versus persistently elevated PTH levels > 6 months after parathyroidectomy. Multivariable Cox regression was used to identify risk factors associated with persistently elevated PTH levels after parathyroidectomy.

Result: Parathyroidectomy was performed in 71 patients with normocalcemic PHPT, of whom 38 (53.5%) had multi-gland disease. No patients became hypercalcemic, with a median follow-up of 23.1 months. Persistently elevated PTH levels were noted in 33 (46.5%) patients. In multivariable analysis, preoperative PTH > 100 pg/mL was associated with persistently elevated PTH levels after parathyroidectomy. In 38 patients with available pre- and postoperative BMD measurements, the mean preoperative BMD improved + 5.6% (p < 0.01) in patients with normalized PTH, while no significant change was observed in patients with persistently elevated PTH levels (- 2.2%, p = 0.47).

Conclusions: Elevated PTH levels are common after parathyroidectomy for normocalcemic PHPT. Improvements in BMD may be predicated on long-term normalized PTH levels following surgery.