[Determination of 25-hydroxyvitamin D serum levels and its seasonal variations in healthy young people]

Abstract

Background: 25-hydroxyvitamin D has a longer half life and its serum levels have less daily variations than calcitriol. Thus, its measurement is a better indicator of vitamin D status.

Aim: To measure 25-hydroxyvitamin D levels in normal subjects during summer and winter.

Patients and methods: Vitamin D was measured using a competitive protein binding radioassay in 61 subjects (27 male) aged 21 to 57 years old, during July and August (winter) and February and March of the next year (summer).

Results: 25-hydroxyvitamin levels were 28.8 +/- 1.5 and 30.9 +/- 2.3 ng/ml during winter and summer respectively. No differences were found between men and women. Ninety five percent confidence levels were between 13 and 50 ng/ml. Levels in one patient with malabsorption were 9.3 ng/ml, in 2 patients with hypophosphatemic osteomalacia were 2.1 and 9.3 ng/ml, in 12 patients with alcoholic cirrhosis were 16.4 +/- 1.3 ng/ml, in 4 patients with primary osteoporosis were 23.3 +/- 0.7 and in three patients receiving vitamin D were 334 +/- 33.2 ng/ml.

Conclusions: Normal levels of 25-hydroxyvitamin D range from 13 to 50 ng/ml in normal adults, there are no differences between men and women and seasonal variations are minimal.