[Seasonal profile of calcium-phosphate metabolism in hemodialysis patients with secondary hyperparathyroidism].

Sunlight UV plays an important role in synthesis of active vitamin D3. Vitamin D3 concentration depends on seasonal sunlight exposure. It was not state, whether these changes may act on secondary hyperparathyroidism (SHP) in hemodialysis (HD) patients. The aim of our analysis was to assess the relationship between seasons and parameters of Ca-P metabolism in HD patients with SHP. We studied 30 pts (F = 17, M = 13), aged 20-72 years (mean 49 +/- 13), duration of HD therapy 3-132 months (mean 54.4 +/- 43.7), treated with alphacalcidol (1 alpha OHD3) due to SHP. Blood was collected for PTH, Ca, P concentrations in January (1), April (IV), July (VII) and October (X); also doses of CaCO3 and 1 alpha OHD3 were analyzed. The day duration was: 7 hours and 51 minutes (I), 12.53 (IV), 16.37 (VII) and 11.39 (X), respectively. PTH concentration was significantly higher in I vs IV (882 +/- 588 vs 691 +/- 511 pg/ml, p < 0.05) and higher in X vs VII (831 +/- 600 vs 701 +/- 525 pg/ml, p < 0.05), despite drug dosage did not differ. Calcium concentration was lower in I vs IV and X, and phosphate concentration was lower in I compared to IV, VII i X. These changes suggest presence of seasonal rhythm of PTH concentration in HD patients with SHP. When assessing the effectiveness of SHP therapy, the season of the year when PTH concentration was tested should be taken into account.