Short and long-term variations in serum calciotropic hormones after a single very large dose of ergocalciferol (vitamin D2) or cholecalciferol (vitamin D3) in the elderly

Context: In humans, few studies have compared the potencies of ergocalciferol and cholecalciferol in improving and maintaining vitamin D status. Objective: Our objective was to evaluate the effects of a single very large dose of both calciferols on serum changes of 25-hydroxyvitamin D [25(OH) D], 1,25-dihydroxyvitamin D [1,25(OH)(2)D], ionized calcium, and parathyroid hormone (PTH) at baseline, and at 3, 7, 30, and 60 d. Design: This was a prospective randomized intervention study. Setting: The study was performed in a nursing home residence. Participants: A total of 32 elderly female patients ( age range 66-97 yr), with vitamin D deficiency was included in the study. Intervention: Participants were randomized into four groups of eight to receive a single dose of 300,000 IU ergocalciferol or cholecalciferol by oral ( os) or im route. Results: 25(OH) D levels sharply increased at d 3 only when vitamins were given os. The 30-d basal difference in serum 25(OH) D was significantly greater after cholecalciferol os administration (47.8 +/- 7.3 ng/ml) compared with other forms (D-3 im: 15.9 +/- 11.3; D-2 os: 17.3 +/- 4.7; D-2 im: 5 +/- 4.4; all P < 0.001). The area under the curve (AUC) of the serum 25(OH) D against time (AUC(60)) was: D-3 os, 3193 +/- 759 ng x d/ml vs. D-2 os, 1820 +/- 512, P < 0.001; and D-3 im, 1361 +/- 492 vs. D-2 im, 728 +/- 195, P < 0.01. 25(OH)D significantly influences PTH levels at 3 (P < 0.03), 7 (P < 0.01), 30 (P < 0.01), and 60 d (P < 0.05). At 60 d, the form of vitamin (cholecalciferol) significantly lowers PTH levels (P = 0.037). Conclusions: Cholecalciferol is almost twice as potent as ergocalciferol in increasing serum 25(OH) D, when administered either by mouth or im. 25(OH) D plays a role in modulating serum PTH.