Estimates of heritability of plasma homocyst(e)ine levels in aging adult male twins.

Plasma homocyst(e)ine level was determined for 96 identical (MZ) and 92 fraternal (DZ) adult male twins aged 59–69. There was no difference in mean between MZ (10.31 nmol/ml) and DZ (10.36 nmol/ml) twins. The intraclass correlation coefficient of the log-transformed homocyst(e)ine level in 43 complete MZ and 39 complete DZ pairs was 0.55 and 0.19, respectively. The MZ correlation was significantly (p<0.05) greater than the DZ correlation, suggesting that the level of plasma homocyst(e)ine is genetically influenced.