Lesion size and cystic morphology are key determinants of parathyroid hormone washout in primary hyperparathyroidism.

Purpose: Accurate preoperative localization of parathyroid adenomas is of great importance to ensure targeted and effective surgical treatment of primary hyperparathyroidism (PHPT). In this context, parathyroid fine-needle aspiration biopsy (FNAB) performed under ultrasound guidance plays a crucial role. This study aimed to evaluate the relationship between ultrasonographic features of parathyroid adenomas and parathyroid hormone washout (PTH-WO) values. Methods: Between January 2022 and August 2024, data from 128 parathyroid adenomas in 122 patients who were prepared for surgery due to PHPT and underwent ultrasound-guided FNAB along with PTH-WO testing were retrospectively evaluated. The obtained PTH-WO results were compared with B-mode and Doppler ultrasound findings. Results: In adenomas with a long axis greater than 10 mm and those containing cystic components, PTH-WO levels were found to be significantly higher (p = 0.005 and p = 0.02, respectively). Additionally, a positive correlation was identified between PTH-WO levels and the short and long axis dimensions of the adenomas. In contrast, no significant relationship was observed between PTH-WO levels and B-mode (grayscale) or Doppler (vascularity) ultrasound features. Conclusion: PTH-WO values vary according to the ultrasonographic dimensions of parathyroid adenomas and are measured at higher levels in cystic adenomas. Other ultrasonographic features do not significantly affect PTH-WO levels. Therefore, the size of the lesion should be taken into account when interpreting PTH-WO results.