Determinants of High Parathyroid Hormone Levels in Patients With Severe Obesity and Their Relationship With the Cardiometabolic Risk Factors, Before and After a Laparoscopic Sleeve Gastrectomy Intervention

Background Obesity is a risk factor for vitamin D deficiency and hyperparathyroidism. Hyperparathyroidism could exert a negative effect on glucose metabolism and vascular function. The aim of this study was to identify the determinants of hyperparathyroidism beyond vitamin D deficiency, whether hyperparathyroidism could have a negative impact on individual health and whether laparoscopic sleeve gastrectomy (LSG) negatively affects the levels of intact parathyroid hormone (iPTH) and 25(OH) vitamin D (25(OH)D). Methods We evaluated the levels of iPTH, 25(OH)D, and leptin, together with markers of insulin sensitivity and early cardiovascular disease, in a cohort of 160 patients with severe obesity before and after an LSG intervention. Results Ninety-seven percent of subjects had vitamin D deficiency, and 72% of them had hyperparathyroidism. After correcting for possible confounders, we found a correlation between iPTH levels and carotid intima-media thickness, as well as with the HOMA index. After the LSG, 25(OH)D levels were significantly increased, while iPTH levels were significantly reduced. The reduction of iPTH was significantly correlated with the reduction of BMI, diastolic blood pressure, and leptin, which was the independent predictor of iPTH reduction. Conclusions Our results suggest that vitamin D deficiency is not the sole determinant of hyperparathyroidism in severe obesity because visceral fat deposition and leptin could both play a role. Obesity-related hyperparathyroidism is associated with insulin resistance and atherosclerosis, although the results from previous studies were conflicting. Finally, LSG intervention does not negatively affect vitamin D status and improves hyperparathyroidism.