Estimating genetic and non‐genetic components of variance for fasting glucose levels in pedigrees ascertained through non‐insulin dependent diabetes

Fasting glucose levels measured on 337 individuals in 14 pedigrees ascertained through a proband with non‐inuslin dependent diabetes were used to estimate genetic and non‐genetic components of variance under a multifactorial model of inheritance. In this sample genetic factors were important in controlling variation in basal carbohydrate metabolism, as represented by age‐adjusted log‐fasting glucose. There was no evidence that arbitrary sib common environments or arbitrary parent common environments accounted for significant portions of the variability in fasting glucose in these data. An arbitrary environment shared by parent and offspring, however, had a marginally significant impact on the likelihood. Parameter estimates obtained from multifactorial models analysed in this manner are sensitive to extreme phenotypic values, however, and caution must be exerciese in estimating total genetic variation. While additive genetic factors did account for a significant proportion of the total variation in fasting glucose, a large proportion remained unexplained.