Changing biochemical presentation of primary hyperparathyroidism

Purpose Patients with primary hyperparathyroidism, pHPT, present with milder symptoms than previously. Some, but not all studies, suggest that this change in clinical pattern also implies lower preoperative parathyroid hormone (PTH) and/or calcium levels and smaller adenomas. This is important since reports indicate that smaller adenomas are more difficult to detect on preoperative imaging, possibly increasing the risk of surgical failure. Methods There were 640 patients with histologically confirmed single-gland pHPT identified in a prospectively collected database. Median values of preoperative calcium, PTH, as well as adenoma weight were compared in three different time periods: 1990-1995, 1996-2000, and 2000-2007. Correlation between the preoperative levels of calcium and PTH and adenoma weight was calculated. Results Preoperative ionized calcium decreased significantly over time (p<0.001). There was a positive correlation between preoperative PTH and adenoma weight (r=0.32, p<0.001). The magnitude of this correlation decreased over time. In women, adenoma weight decreased significantly over time (p=0.03). Median (25th-75th percentile) adenoma weight in women was 750 (400-1,380) mg, 650 (350-1,205) mg, and 520 (305-1,065) mg in the first, second, and third period, respectively. Conclusion From 1990 to 2007, there was a significant trend to operate pHPT patients with lower preoperative serum ionized calcium levels. In women, the adenoma weight decreased. This trend could potentially lead to decreased sensitivity in preoperative localization procedures.