Can we predict expected adenoma weight preoperatively with reference to the correlation of preoperative biochemical tests with parathyroid adenoma weight?

Background: Primary hyperparathyroidism is a prevalent disease with proven benefits for appropriately selected patients who undergo parathyroidectomy. The ability to accurately predict expected single adenoma gland weight as the cause based on preoperative biochemical tests could improve cure rates in a minimally invasive approach. Objective: To assess the correlation between parathyroid weight and preoperative parathyroid hormone and calcium levels in patients with primary hyperparathyroidism with a solitary adenoma and determine if these could be used to predict expected parathyroid weight. Methods: Patients with primary hyperparathyroidism who underwent curative parathyroidectomy from 2013 to 2018 was retrospectively analysed. Results: There is a strong positive correlation r = 0.602 between preoperative PTH levels with respect to parathyroid weight (p \u3c 0.001). There was a moderate correlation r = 0.474 between preoperative adjusted Calcium and PTH weight (p \u3c 0.001). An algorithm was developed to calculate predicted weight of a single adenoma but when tested against cases with hyperplasia and double adenomas during the period, the variability of predicted weight meant it was impossible to differentiate between the causes. Hyperplasia was excluded and 95% of double adenomas excluded however, when parathyroid weight exceeded 1200 mg. Conclusion: There is a strong correlation between preoperative PTH levels and calcium levels with parathyroid weight. The large variability of predicted parathyroid weight however, precludes the use of biochemical tests alone preoperatively in being able to differentiate between a single adenoma, double adenoma or hyperplasia as the cause in primary hyperparathyroidism. At parathyroid predicted weights above 1200 mg however, all cases of hyperplasia, and 95% of double adenomas excluded