Relationship between parathyroid hormone level and parathyroid gland size and numbers in renal hyperparathyroidism

Background: Serum parathyroid hormone (PTH) is the gold standard for the diagnosis of renal hyperparathyroidism. Persistent hyperparathyroidism in chronic kidney disease patients results in hyperplasia of the parathyroid glands. Therefore, parathyroid gland size may be an alternative marker to assess the severity of hyperparathyroidism. Objective: The aim of our study is to investigate the relationship between serum PTH levels and the size and number of parathyroid glands in patients with renal hyperparathyroidism. Methods: We retrospectively identified patients with renal hyperparathyroidism who underwent focused ultrasound of the parathyroid glands at our institution between August 1st, 2010, and June 30th, 2019. The sum max diameters and numbers of parathyroid glands were collected and compared with serum PTH levels. Results: A total of 110 parathyroid glands in 40 patients were identified. There was a positive correlation between serum PTH levels and the sum max diameters of parathyroid glands (r = 0.397, P < 0.05). There is a trend toward statistical significance in predicting parathyroid enlargement (≥ 3 glands) (AUC=0.659, 95% CI: 0.482-0.836, P=0.085). At a cut-off PTH level of more than 2100 pg/ml, high specificity (>81%) was achieved for the detection of ≥ 3 parathyroid gland enlargements. Conclusions: The serum PTH level in patients with renal hyperparathyroidism is positively correlated with parathyroid gland size. Patients with higher serum parathyroid hormone levels also tend to have an increased number of parathyroid glands. Discrepancy between parathyroid gland size and serum parathyroid hormone level may suggest further exploration for additional parathyroid gland.