STUDY OF THE GENETIC AND EXTRA-GENETIC DETERMINANTS OF ALPHA-KETOSTEROID PRODUCTION IN MAN

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Abstract
The steroid patterns of normal adult, male, dichorionic, monozygotic triplets were examined in detail during control periods and during stimulation with adrenocorticotropic hormone (ACTH). In 2 of the triplets these patterns were virtually identical before, during, and after ACTH administration. In view of the highly individual nature of these patterns, this is impressive evidence of a genetic influence on steroid hormone production and metabolism in man. The 3d triplet, however, produced significantly smaller amounts of individual keto-steroids, as compared with his brothers, during all periods. This finding is interpreted as evidence for the existence of an extra-genetic influence by means of which steroid production or metabolism had been modified. Related physiological differences in monochorionic twins have been attributed to demonstrated vascular asymmetry and unequal distribution of the mutual fetal circulation to one partner of the pair. The birth membranes of these triplets were dichorial in character and it is evident that a fetal situation comparable with that seen in monochorionic twins existed for 2 of the brothers. It is presumed, therefore, that the triplet with divergent steroid patterns was the deprived member of this pair and that his differences in production or metabolism of steroids represent a physiological aftermath of a relatively deficient fetal circulation.