Background: Parathyroid carcinoma (PCa) is a rare disease that can be difficult to differentiate initially from benign parathyroid adenoma. PCa over-secrete the amino form of parathyroid hormone (PTH), which is recognized by 3rd generation but not by 2nd generation (intact) PTH assays. In normal individuals, the 3rd generation/2nd generation PTH ratio should always be <1.
Material and methods: We studied the utility of the 3rd generation/2nd generation PTH ratio as a means of distinguishing PCa patients (n=24) from control groups with and without disorders of calcium secretion, including patients on renal hemodialysis (n=73), post-renal transplantation (60), elderly healthy (n=82) and primary hyperparathyroidism (PHP; n=30). 2nd and 3rd generation PTH were assayed with the PTH Duo kit (Scantibodies, Shantee, CA, USA).
Results: The mean 3rd generation/2nd generation PTH ratio was 0.58±0.10 in the dialysis patients, 0.54±0.10 in the renal transplant group, 0.54±0.12 in the elderly healthy patients and 0.68±0.11 in the PHP group. All 245 of these patients presented a 3rd generation/2nd generation PTH ratio of <1. In contrast, we observed an inverted 3rd generation/2nd generation PTH ratio >1 in 20 PCa patients, whereas only 4 PCa patients had a normal ratio of <1.
Conclusions: An inverted 3rd generation/2nd generation PTH ratio occurred in the majority of patients with advanced PCa and was absent in all 245 relevant controls. A 3rd generation/2nd generation PTH ratio >1 had a sensitivity of 83.3% and a specificity of 100% amongst PHP patients as a marker for PCa; among all published cases, the sensitivity was 75.8% and the specificity was 98.9%. This ratio may be useful to identify patients with PCa earlier, and to detect patients either at risk of developing PCa or those in whom recurrence is occurring.
Prague, Czech Republic
24 - 28 Apr 2010
European Society of Endocrinology