Endocrine Abstracts (2010) 22 P434

Identification of hyperfunctioning parathyroids (HP) in primary hyperparathyroidism (pHPT) in the presence of concomitant thyroid diseases

Francesco Boi1, Maria Chiara Cocco1, Cira Lombardo1, Ivan Maurelli1, Mario Piga2, Maria Letizia Lai3, Angelo Nicolosi4 & Stefano Mariotti1

1Endocrinology, Department of Medical Sciences M. Aresu, University of Cagliari, Cagliari, Italy; 2Nuclear Medicine, Department of Medical Sciences M. Aresu, University of Cagliari, Cagliari, Italy; 3Department of Cytomorphology, University of Cagliari, Cagliari, Italy; 4Department of Surgery, University of Cagliari, Cagliari, Italy.

Purpose: To characterize the interference of concomitant thyroid diseases in the localization of HP in pHPT and develop a valuable diagnostic strategy.

Subjects and methods: Forty pHPT patients were selected for the presence of coexistent thyroid nodules (TN) or Hashimoto’s thyroiditis (HT). Neck ultrasound (US) and sesta-MIBI scintigraphy (MIBI) were performed in all cases. US and MIBI were concordant in 16 cases (group I) while in the remaining 24 (group II) images were discordant leading to the identification of 42 poorly defined nodular lesions within or nearby the thyroid bed. In both groups all lesions were submitted to PTH assay in fine needle aspiration fluid (FNA-PTH). Patients were eventually operated and HP identified at histology.

Results: US and MIBI correctly identified HP in all group I patients. In group II US correctly identified 21/25 HP (sensitivity 84%; specificity 82%) and MIBI only 13/25 HP (sensitivity 52%; specificity 25%). The main causes of false positive (8/16=50%) MIBI images were represented by TN (3 oncocytic neoplasias, 2 hyperfunctioning adenomas, 2 hyperplastic nodules and 1 papillary thyroid carcinoma), while 6/12 (50%) false negatives were associated with HT. Interestingly, the percentage of false negative MIBI images was significantly lower in the remaining cases without associated HT (3/28=10.7%), P<0.01. PTH-FNA correctly identified all HP in both groups (100% sensitivity and specificity).

Conclusions: TN or HT may cause variable degrees of mismatch between MIBI and US in HP localization with false positive and negative MIBI images. TN represent the most frequent cause of false positive, while HT appears to be responsible of most false negative images. PTH-FNA represents the best diagnostic tool for the identification of HP and should be preferentially employed in the presence of concomitant thyroid diseases.

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