PTH and secondary hyperparathyroidism: In the distal LRYGB group, significantly more patients had an increased parathyroid hormone level (PTH, > 6.9 pmol/l) than the proximal cohort at 5 years post-surgery (59/96 vs. 13/59, p < 0.001), but the two cohorts did not show a significant difference in the prevalence of secondary hyperparathyroidism (PTH > 6.9 pmol/l and calcium < 2.2 mmol/l) (12% vs. 8%, p = 0.65).