Incidence of Ectopic Parathyroid Glands in Primary, Secondary, and Tertiary Hyperparathyroidism

In patients undergoing surgery for hyperparathyroidism (HPT), ectopic parathyroid glands can often make the operation challenging. Understanding the most common locations of ectopic parathyroids may provide guidance if an abnormal gland cannot be found intraoperatively. The aim of this study is to identify the frequency and anatomical patterns of ectopic parathyroid glands in patients with primary, secondary, and tertiary HPT.

A retrospective cohort analysis was performed on 3029 patients with primary, secondary, and tertiary HPT who underwent parathyroidectomies from 2001 to 2023. Patients with ectopic glands (n = 627) were stratified by type of HPT and ectopic location. Ectopic parathyroid glands were categorized into six anatomical locations: thymic, intrathyroidal, retroesophageal, mediastinal, undescended, or carotid sheath. Chi-square analysis and pairwise Fisher's exact tests were conducted to assess statistically significant differences in ectopic gland location distribution across all HPT subtypes.

The incidence of ectopic parathyroid glands in primary HPT (25%), secondary HPT (25%), and tertiary HPT (24%) was strikingly similar. Of the 627 patients with ectopic parathyroid glands, the most common ectopic location was thymic (50%), followed by intrathyroidal (23%), retroesophageal (17%), mediastinal (5%), undescended (4%), and the carotid sheath (2%).

There appears to be no significant difference in the incidence and distribution of ectopic parathyroid glands among patients with primary, secondary, and tertiary HPT. The thymus is the most common location across all three subtypes of HPT, and cervical thymectomy could be considered during parathyroidectomy if an abnormal gland cannot be found.