Vitamin D status, physical performance and body mass in patients surgically cured for primary hyperparathyroidism compared with healthy controls - a cross-sectional study

Objective Low plasma 25-hydroxyvitaminD (25OHD) levels, reduced muscle strength and increased body mass index (BMI) are well-known characteristics of primary hyperparathyroidism (PHPT). Mechanisms for low 25OHD levels, increased BMI and potential changes after parathyroidectomy are unknown. Muscle strength is reported to increase following surgical cure, but whether the improvement corresponds to healthy controls' performances remains largely unknown. Patients We studied 51 patients with former PHPT [mean age 61(36-77) years] successfully treated by surgery [mean time since operation 7.4(5-15) years] and 51 sex- and age-matched controls. Measurements Physical performance include "repeated chair stand" (RCS), "timed up and go" (TUG), muscle strength [hand grip, elbow flexion/extension and knee flexion/extension (60 degrees/90 degrees)], postural stability, biochemistry and anthropometric indices. Results Forty-one cases had pathologically verified adenoma, three had hyperplasia and three had uncertain diagnosis whereas four had missing data. Dietary calcium intake, vitamin D supplementation and biochemistry including PTH and 25OHD levels did not differ between groups. Former patients had significantly higher BMI (28.8 +/- 6.0 kg/m(2)) than controls (26.0 +/- 4.7kg/m(2)). Muscle pain was more frequently reported by cases than controls, and cases performed RCS slower than controls (P = 0.02). Furthermore, female cases had lower muscle strength in knee flexion 60 degrees (P = 0.02) and 90 degrees (P = 0.05). Former patients no longer differed from controls after adjustment for BMI. Conclusion Following cure, 25OHD levels are normalized suggesting 25OHD insufficiency is not a constitutional characteristics in patients with PHPT. Increased BMI seems to be sustained. Whether this is caused by decreased muscle strength or reduced muscular performance causes adiposity needs further investigations.