Endocrine Abstracts

Introduction: An accurate identification of affected parathyroid is crucial for implementation of mini-invasive surgery techniques and therefore reduction of complication rate. A few centers postulate measuring washout parathormone (PTH)concentrationin suspected lesions, despite lack of established cut-off point for concentration values and validated measurement methods. Thisprospective study aimed to compare washout PTH assessment vs MIBI scintiscan in terms of efficacy in localization of parathyroid adenoma (PTA) in patients with hyperparathyroidism (HPT).

Material and Methods: 55 consecutive HPT patients (including seven males) aged 59 ± 12 years were included. Median serum PTH was 133 mg/dl (range 83–148; normal 15–57), total calcium 11.2 ± 1 mg/dl, ionized calcium 6.1 ± 0.7 mg/dl, phosphates 2.8 ± 0.6 mg/dl. Median maximum diameter of the lesion was 8 mm (range 3–40) on ultrasound. The most common location was left lower thyroid pole (n = 18). The needle washout was performed in 1ml 0.9% NaCl. PTH concentration was measured by electro-chemiluminescence third-generation immunoassay Elecsys PTH 1–84 using cobas e 801 analyzer. Thyroid and parathyroid ultrasound was performed by an AIXPLORER system (Supersonic Imagine, Aix en-Provence, France).

Results: Median PTH washout concentration was 1493 pg/ml (range 17.2–5000). Positive PTH washout result (≥ 3 times above serum PTH value), was obtained in 76% of subjects. In lesions with ultrasound picture typical of PTA (n = 45), PTH washout was positive in 82%. PTH values were significantly higher in typical than atypical lesions (P = 0.026). Among patients with negative PTH washout (n = 13), 85% had nodular goiter and/or autoimmune thyroid disease (AITD). MIBI performed in 53 patients, provided localization of PTA in 68%. In subgroup with negative MIBI, 13 subjects (76%) had positive PTH washout (location confirmed surgically in 3, 8 awaiting surgery, 2 followed-up).According to clinician, more useful in terms of PTA location was PTH washout alone in 30% of cases, especially in lesions <1 cm (33% vs 25% for MIBI), MIBI alone in 21% of cases, for the rest both methods were equivalent.

Conclusions: PTH washout assessment using the same method as for serum PTH measurement isa reliable method of PTA localization,particularly useful for lesions <1cm, with typical ultrasound features of PTA, without concomitant nodular goiter or AITD and negative MIBI results, although is not yet widely validated by lab technicians. Despite slight preponderance of PTH washout above MIBI alone, combination of both methods seems to be the most valuable. The study will be continued to reach relevant endpoint after surgery.