Correlation of perioperative biochemical variables with single adenoma weight in patients with primary hyperparathyroidism

BACKGROUND: Single parathyroid adenoma is the main cause of primary hyperparathyroidism (PHPT), with surgery remaining the gold standard for its treatment. The ability to preoperatively predict the parathyroid adenoma size and could facilitate the decision about the extent of surgical exploration. It is reasonable to hypothesize that the perioperative levels of PHPT-related variables (i.e. calcium, parathormone, phosphate) may predict the adenoma weight or/and demonstrate whether the adenoma is successfully removed or not. Aim of this study is to explore the relationship between perioperative biochemical values and adenoma weight. Secondarily, we investigated the relationship between adenoma weight and uni-/bilateral neck exploration. METHODS: Retrospective study of all patients undergone surgery for primary hyperparathyroidism due to single adenoma in a tertiary university hospital in Germany during a 6-year period. Following variables were analyzed: preoperative serum calcium, phosphorus and parathormone, intraoperative parathormone before and after adenoma excision, intraoperative PTH decrease, postoperative serum calcium and parathormone (PTH(postop)—pg/ml), calcium and PTH decrease. Bivariate correlations were calculated by the Spearman's correlation test at the 95% significance level. RESULTS: A total of 339 patients were included in the study. The median age of the patients was 60 years (range 21–90) and 77% were females. The median adenoma weight was 1 g (range 0.1–11). Adenoma weight correlated strong with maximum adenoma diameter (r = 0.72, p < 0.05), moderate with preoperative parathormone (r = 0.44) and parathormone decrease (r = 0.27), whereas there was no correlation with the intraoperative PTH decrease (r = 0.02). There was also a borderline (moderate to weak) correlation with pre- and postoperative calcium levels (r = 0.21 and r = 0.23 respectively) and a negative borderline correlation with phosphorus (r = − 0.21). Patients who required bilateral neck exploration, had significantly lighter adenomas (median weight 0.8 g vs 1.1 g, p = 0.005). CONCLUSIONS: We conclude that preoperative PTH levels may only serve as an approximate guide to adenoma weight, as direct preoperative prediction is not possible. Serum calcium levels, PTH and calcium decrease correlate only weak with adenoma weight. Patients who require bilateral neck exploration, have significantly (20–25%) lighter adenomas.