Familial influences on the adrenal androgen excretion rate during the adrenarche

The regulation of adrenal androgen (AA) production in both children and adults has not been defined. We report here on two different studies that examined familial influences on AA production early in life when such production is accelerated, a period known as the adrenarche. AA production was estimated from measurements of excretion of AA in urine samples collected overnight. The first study used a twin model where genetic and environmental components to the variance in AA excretion were determined in white monozygotic (MZ) and dizygotic (DZ) twins. The intraclass correlation coefficient for weight-adjusted AA excretion was .730 (P < .0001) in MZ twins and .511 (P = .007) in DZ twins. There was a significant genetic component to the weight-adjusted AA excretion rate, with a heritability of 58%. Environmental effects accounted for 17% of the variation. Black children were previously shown to have higher AA levels than white children. Therefore, in the second study we looked for evidence that race affected familial influences on AA excretion. To estimate familial aggregation of AA excretion, intraclass correlations were determined in siblings from black and white families. AA excretion rates were measured twice-yearly for up to 4.5 years, and an individual's average excretion rate was used in the analysis. The intraclass correlation coefficient for the weight-adjusted AA excretion in black siblings was .492 (P = .0021), and for white siblings it was .372 (P = .0003). Intraclass correlation coefficients for AA excretion rates were not significantly different in the two racial groups.(ABSTRACT TRUNCATED AT 250 WORDS)