Abstract Background Parathyroid carcinoma is a rare but highly aggressive cause of primary hyperparathyroidism. Although malignant tumours typically present with markedly elevated PTH levels and pronounced hypercalcemia, they also tend to be substantially larger than benign adenomas. Emerging observations suggest that, despite high absolute serum PTH concentrations, the secretory activity per unit of tumour volume may be lower in carcinomas. This altered biochemical profile may enhance preoperative differentiation between malignant and benign parathyroid disease. Methods We retrospectively analysed 341 patients undergoing surgery for PHPT between 2017 and 2024. Parathyroid carcinoma was diagnosed in 8 patients (group 1), while 333 had benign lesions (group 2). For each case, a PTH/volume index was calculated (serum PTH in pg/mL divided by tumour volume in mL). Statistical analyses included intergroup comparisons and logistic regression. Results Despite higher absolute PTH values and substantially larger tumour volumes in carcinoma cases, the PTH/volume index was significantly lower in group 1 than in group 2 (116.08 vs. 443.12; U = –2.54, p = 0.011). Each one-unit decrease in this ratio was associated with a 1% increase in the likelihood of carcinoma (OR = 0.99; p = 0.04), reflecting reduced secretory efficiency relative to tumour size. Conclusions Parathyroid carcinomas demonstrate disproportionately low secretory activity despite large tumour mass and high total PTH levels. The PTH-to-volume ratio may therefore serve as a valuable preoperative marker for identifying malignant lesions. Prospective validation is warranted.
Laurino et al. (Fri,) studied this question.
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