Endocrine Abstracts

Introduction: Parathyroid carcinoma (PCa) is a rare presentation of primary hyperparathyroidism (PHPT), accounting for less than 1% of cases. Differentiating parathyroid cancer from benign hyperparathyroidism is clinically challenging. Some previous work suggest that there is a paraneoplastic hCG production in parathyroid cancer (Stock et al 1987, Rubin et al 2008). In this study, we aimed to investigate whether the hCG+β kit from Roche Diagnostics could distinguish PCa patients from primary and secondary hyperparathyroidism. Additionally, we validate hCG levels according to renal function and determine hCG test sensibility and specificity to diagnose parathyroid cancer.

Material and methods: We studied a series of eight patients suffering from advanced PCa, referred to the CHU de Liege. A group of 20 PHPT patients and 25 patients with secondary hyperparathyroidism (SHP) due to chronic renal failure were used as controls. hCG+β kit on Cobas (Roche Diagnostics) uses 2 monoclonal antibodies that recognize holo-hCG, nicked hCG, β-core fragment and free β-subunit. Limits of hCG detection and quantification are <0.1 and <0.6 mUI/ml. In non pregnant and postmenopausal women and in men, hCG (p95) is <1 (5.3), <7 mUI/ml (8.3) and <2 (2.6) mUI/mL, respectively.

Results: The 8 PCa patients (3 women) presented high serum hCG values at: 1.29, 3.46, 5.7, 24.2, 31.2, 34.1, 36.5 and 164 UI/l. Values of 1.29 and 3.46 were obtained in 2 postmenopausal women. The lowest value was presented by the only still alive patient who had hormonal and biochemical normalization and tumor shrinkage induced by anti-parathyroid hormone immunotherapy (Betea et al. 2004). In cancer patients, there was a significant correlation (r=0.786; P<0.05) between hCG and PTH whereas median hCG (5.7 UI/l) was significantly higher than in PHP (1.25 UI/l) and SHP (0.97 UI/l). hCG test sensitivity was 75% and specificity was 94% to detect parathyroid cancer, with a cutt-off of hCG of more than 5.68 UI/l.

Conclusions: These results suggest that serum hCG might have the potential to discriminate between parathyroid adenomas and carcinomas, with a sensibility of 75% and a specificity of 94%. The only patient still alive who underwent a PTH immunotherapy, presented the lowest hCG values. If hCG could be predictive of PCa survival needs to be studied in a larger series of patients. A future area of research revealed by this data is to test hCG immunotherapy in parathyroid cancer.