Endocrine Abstracts

Parathyroid localization by fine needle aspiration and parathyroid hormone (PTH) washout measurement is not a widely accepted method because of possible alterations in parathyroid histology. However, when performed with technical competence this easily available method has been praised to be an immediate confirmation of enlarged parathyroid glands found on ultrasound. We retrospectively reviewed primary hyperparathyroidism (PHPT) patients with previously performed PTH washout in pathologically confirmed parathyroid adenoma or hyperplasia. Their biochemical and anthropometric data, the size and location of analyzed parathyroid glands and concordant thyroid sonographic features were collected. Among 48 included patients, PTH washout measurement was available for 51 operated glands. In only 5 cases PTH washout level was lower than patient’s serum PTH value. In this analysis we applied a stringent criterion: the ratio between the PTH washout level and serum PTH (PTH W/S) ≥2 was considered unequivocally positive. The sample was divided in two groups: 39 cases with positive PTH W/S and remaining 12 cases that did not reach this cutoff. In the comparison between investigated groups there was no difference in serum and urine calcium or PTH elevation. Body mass index, the upper or lower location of parathyroid glands and the presence of concomitant thyroid nodules or ultrasound features of diffuse thyroid disease were not different between groups. The volume and the maximal diameter of enlarged parathyroid glands measured by ultrasound were significantly larger in the group with positive PTH W/S (P<0.05), while the minimal parathyroid diameter was not different between groups. For parathyroids that have a volume lower than 0.145 ml the odds ratio for not obtaining positive PTH W/S was 8.75 (CI 1.47–56.67). Adverse events or later surgical and pathological complications related to PTH washout procedure were not reported. While location, concomitant thyroid disease and patient obesity did not show a significant role in obtaining a positive PTH washout, the size of diseased glands remains the biggest challenge in parathyroid localization. It has significant impact on the accuracy of almost all available imaging methods. Considering that small size might be also associated with multigland PHPT, optimal diagnostic steps should be carefully planned. Doubts about the safety of parathyroid fine needle aspiration need to be finally solved with further analysis in large series of histological specimens.