[Radiocompetitive dosage of 25 hydroxyvitamin D and 24, 25-dihydroxyvitamin D in geriatrics. Study of seasonal variations].

: Dosages of 25 (OH) D and of 24, 25 (OH) 2 D in the plasma were done in March and October in 26 women more than 70 years old, hospitalized in a semi-chronic disease hospital of the Paris area. Eleven young adults, studied in June, served as control. There was a significant decrease of 25 (OH) D and 24,25 (OH) 2 D in older individuals (pL 0,001). In march, the levels of 25 (OH) D and 24,25 (OH) 2 D were respectively 2,7 +/- 1,6 mg/ml and 0,88 +/- 0,53 mg/ml. In October the level of 25 (OH) D (5,8 +/- 2,6 mg/ml) were significantly higher (p L 0,01) whereas the level of 24,25 (OH) 2 D did not vary (0,84 +/- 0,58 mg/ml). These results are in agreement with those obtained in England. The underline the relative deficit vitamin D in older individuals. The constant decrease of 24, 25 (OH) 2 D remained unexplained.