Hewitt S, et al. - Here, the researchers aimed to examine the prevalence of secondary hyperparathyroidism (SHPT) and its relation to vitamin D status. Two years after gastric bypass, the highest prevalence of SHPT was observed in vitamin D deficient patients. Compared with lower target levels, parathyroid hormone (PTH) and the prevalence of SHPT were notably lower with S-25(OH)D ≥100 nmol/l.

Methods

• The researchers designed this cross-sectional study at Oslo University Hospital, Norway.
• They enrolled 502 consecutive patients (22-64 years) attending 2-year follow-up after Roux-en-Y gastric bypass.
• They considered a serum intact PTH >7.0 pmol/l in the absence of elevated serum ionized calcium (iCa) as SHPT.
• They defined vitamin D status by serum concentrations of 25-hydroxyvitamin D (S-25(OH)D).

Results

• The researchers found SHPT in 171 patients (34%).
• Across the range of S-25(OH)D (P<0.001), the prevalence of SHPT varied, being highest (71%) with S-25(OH)D <25 nmol/l.
• The prevalence of SHPT was lower with S-25(OH)D ≥50 nmol/l (29.0%; RR=0.64 (95%-CI:0.50-0.81)) and S-25(OH)D ≥75 nmol/l (27.7%; RR=0.61 (95%-CI:0.44-0.84)) compared with S-25(OH)D <50 nmol/l.
• S-25(OH)D ≥100 nmol/l was correlated with the lowest PTH and the lowest prevalence of SHPT (16.0%; RR=0.35 (95%-CI:0.14-0.88) compared with S-25(OH)D <50 nmol/l), and the most normal calcium distribution.
• In this study, these associations were most pronounced with iCa in the lower range.
• They found a synergistic association for S-25(OH)D and iCa on SHPT.