Effects of Inactive Vitamin D on Persistent Secondary Hyperparathyroidism in Patients on Hemodialysis

Secondary Hyperparathyroidism (sHPT) is an important feature of chronic renal failure and contributes to the development of renal osteodystrophy. This study was carried out to assess 25(OH)D status and its effect on sHPT in patients on hemodialysis (HD). A prospective experimental trial of 180 HD patients (F: 81, M: 99, age > 14year) participated in the study. At base line, levels of 25(OH)D, intact Parathyroid Hormone (iPTH), Calcium (Ca), Phosphorous (P), Alkaline phosphatase (Alk p), and albumin of serum were measured. Patients with 25(OH)D deficiency (< 30 ng/mL) were randomly divided to two groups: intervention (received 300,000 U/IM vitD3 at the beginning and after 2 months, if was necessary) and control (received placebo). After 2 and 4 months, the same biochemical markers were measured and efficacy of vitD3 on sHPT was assessed. Secondary Hyperthyroidism (sHPT) was defined as iPTH > 300 pg/mL. Serum 25(OH)D levels were deficient in 87.8% (n: 158) of subjects, and normal in 12.2% (n: 22). The prevalence of sHPT, according to 25(OH)D levels, was 71.5% (n: 113)(< 30 ng/mL) and 40.9% (n: 9)(≥ 30), respectively. There were 57 intervention and 56 control subjects. In the intervention group, 2 months after injections, 25(OH)D increased from 13.85 ± 6.5 to 48.5 ± 20.7 (P < 0.001), iPTH was reduced from 567.2 ± 276.7 to 282.7 ± 183.6 (P < 0.001), calcium from 9.10 ± 0.5 to 8.76 ± 0.7 (P = 0.021), Alk p from 553.37 ± 495.6 to 393.4 ± 419.5 (P < 0.001), albumin from 3.87 ± 0.5 to 4.00 ± 0.4 (P = 0.06), and phosphorus from 4.90 ± 1.2 to 5.21 ± 1.3 (P = 0.12). Since all cases were under appropriate treatment for sHPT, there was a significant reduction on the levels of iPTH (P = 0.005) and Alk p (P = 0.049), and slight increase in 25(OH)D level (P = 0.08 ) in the control group. However, the amount of these changes was less than the intervention group. These findings showed that 25(OH)D insufficiency was highly prevalent in HD cases and higher amount of 25(OH)D levels prevent sHPT.