Biological variation of retinoids in man.
This investigation was undertaken to assess biological variation, especially the within-subject variations of all- trans retinoic acid, 13- cis retinoic acid and retinol in human serum. Diurnal variation and variation over a week, a month and a year were studied in 11 males (aged 21 - 54 years) and 17 females (aged 22 - 63 years), all subjectively healthy. We found no diurnal variation with the ex
