The Impact of Moderate Hypophosphatemia on the Clinical Management of Primary Hyperparathyroidism.

Background and objective The impact of moderate hypophosphatemia (hypoP) on primary hyperparathyroidism (PHPT) and its use as an independent surgical criterion has not been adequately evaluated in the literature. In light of this, we conducted this study to address the scarcity of data on this topic. Methods We conducted a retrospective evaluation of data related to 164 (133 females and 31 males) patients with PHPT who met the criteria for inclusion in the study. HypoP, which is indicated by phosphorus (P) levels lower than 2.5 mg/dL, was found in 78 (47.5%) patients, and moderate hypoP (1-1.99 mg/dL) was found in 25 patients (15.2%). Results PHPT severity was worse in hypoP patients than non-hypoP patients, as evidenced by higher levels of mean serum calcium (12.9 ±1.0 mg/dL vs. 11.1 ±0.3 mg/dL respectively, p<0.001), parathormone (PTH) [median (interquartile range, IQR): 455.3 (455.3) ng/L vs. 124.0 (84.0) ng/L respectively, p<0.001] and mean 24-hour urinary calcium (414.6 ±168.5 mg/day vs. 291.5 ±161.4 mg/day respectively, p=0.026) as well as lower levels of mean BMI (25.6 ±3.9 kg/m2 vs. 29.0 ±4.0 kg/m2 respectively, p=0.18) and mean 25-hydroxy vitamin D3 (13.8 ±7.3 µg/L vs. 18.2 ±7.8 µg/L respectively, p=0.001). Among the whole study population as well as among patients with Ca levels <1.0 mg/dL according to the upper limit of normal, P level was determined to be an independent factor affecting the indication for surgical treatment [β: -1.96,p=0.038, odds ratio (OR): 0.14, 95% confidence interval (CI): 0.02-0.89 and β: -2.3, p=0.034, OR: 0.10, 95% CI: 0.12-0.84 respectively]. Conclusion We found a strong correlation between moderate hypoP and the severity of the biochemical manifestations of PHPT. In asymptomatic PHPT patients, moderate hypoP was predictive of surgical indication, independent of age and level of hypercalcemia.