A study in twins of the urinary excretion of vanilmandelic acid, 17-keto-steroids, 17-hydroxycorticosteroids, and creatinine]

The 24-hour urinary excretion rates of creatinine, vanilmandelic acid (VMA), 17-hydroxycorticosteroids, 17-ketosteroids were analysed in 30 female twin pairs. For each of these variables, a comparative study based on the breakdown of total variance into interpair and intrapair variance was undertaken, first on identical (MZ) and fraternal (DZ) twins and then on twins who live together or separately. The comparison of test results shows a strong likeness in the MZ group and in the living together group with respect to the urinary excretion of 17-OH. The variability of VMA excretion can be explained by genetic factors while the variability of 17-ketosteroids and creatinine can be explained with reference to environmental factors.