Persistently elevated parathyroid hormone after successful parathyroid surgery.

Objectives/hypothesis: Explore potential causes of persistently elevated parathyroid hormone levels after curative parathyroidectomy in patients with primary hyperparathyroidism due to single gland disease.

Study Design: Case series with planned data collection.

Methods: An analysis was undertaken of 314 patients with primary hyperparathyroidism undergoing parathyroid surgery in a tertiary academic practice between January 2009 and April 2013. There were 187 patients with single-gland disease; 68 failed to meet inclusion criteria, resulting in a study population of 119 patients. Preoperative parathyroid hormone, calcium, ionized calcium, 25-OH-vitamin D, creatinine, and glomerular filtration rate values were determined, along with postoperative calcium, ionized calcium, and parathyroid hormone levels. Patients were divided into two groups based on their postoperative parathyroid hormone values: elevated parathyroid hormone and normal parathyroid hormone.

Results: Thirty (25.2%) patients achieved postoperative normocalcemia but had elevated parathyroid hormone levels. This group had significantly higher preoperative levels of parathyroid hormone (P =.002) and creatinine (P =.007), and a lower glomerular filtration rate (P =.002) than patients with normal postoperative parathyroid hormone levels. The preoperative 25-OH-vitamin D level was not significantly associated with an elevated parathyroid hormone (odds ratio [OR]: 1.56). Preoperative impaired renal function, specifically an abnormal glomerular filtration rate (OR: 12.8), was significantly associated with an elevated parathyroid hormone.

Conclusions: Parathyroid hormone remains elevated in 25% of patients who are cured (eucalcemic) after surgery for primary hyperparathyroidism. This phenomenon was associated with higher preoperative parathyroid hormone levels and impaired renal function rather than low 25-OH-vitamin D levels.

Level Of Evidence: 4. Laryngoscope, 127:1720-1723, 2017.