Endocrine Abstracts

The oral dosing with cholecalciferol needed to achieve and maintain optimal serum concentration 25-hydroxyvitamin D (25OHD) is still controversial.

This study reports on the efficacy of supplementation with oral vitamin D3 1000 U/day for 3–18 months on serum 25OHD levels in 87 ambulatory patients with postmenopausal osteoporosis (mean age 63.5 years). Serum 25OHD, parathyroid hormone (PTH), calcium (serum, urine), phosphate, alkaline phosphatase and creatinine were measured before and after 3 mo (54 pts), 6 mo (27 pts), 9 mo (15 pts), 12 mo (25 pts), 18 mo (5 pts) of oral vitamin D supplementation.

At baseline, using a cut-off point of sufficiency of 30 ng/ml, 10.34% of patients were deficient (mean=7.77 ng/ml), 82.76% were insufficient (mean=16.19 ng/ml) and 6.9% were sufficient (mean=35.86 ng/ml).

After 3 months of supplementation none of the patients was deficient, 64.81% were insufficient (mean=22.91 ng/ml) and 35.19% were sufficient (mean=36.79 ng/ml). The increment in serum 25OHD was inversely related to the starting level (r=0.78). The average increments were: 20.24 ng/ml (0.81 ng/ml for every μg), 11.89 ng/ml (0.47 ng/ml), and 3.86 ng/ml (0.15 ng/ml) in deficient, insufficient and sufficient groups, respectively. Mean serum PTH concentrations decreased significantly (P<<0.001), as did alkaline phosphatase (P=0.002).

In 28 patients with follow-up data beyond 3 mo of supplementation there were 22 patients still insufficient at 3 or 6 mo, 15 of them reaching optimal concentration up to 18 mo. Six patients sufficient after 3 or 6 mo maintained their levels until the end of the follow-up.

In conclusion, oral vitamin D3 supplementation with 1000 UI/day is adequate to achieve (time-dependent) and maintain optimal serum 25OHD concentration for more than half of them. As many patients do not achieve these goals even after a long follow-up we suggest that checking of vitamin D status and refining of the dose are required.