S5  GENETIC SUSCEPTIBILITY IN MALE AND FEMALE BALDING

Messenger A.G., Birch M.P.  Department of Dermatology, Royal Hallamshire Hospital, Sheffield, UK

Early investigators proposed that both male and female balding are due to a single gene. More recently it has been suggested that balding is a polygenic trait. However, two factors have complicated the study of the genetics of balding. Firstly, in both sexes the phenotype is age-dependent and may only be fully expressed in the elderly. Secondly, it is not clear whether female pattern balding is the same entity as male balding. To address these problems we have studied family histories of balding in a large cohort of men and women with a wide range of ages and drawn from the same population.

As in previous studies we found that balding is more common in the fathers of young balding men than in the population at large (RR 1.35). We also found that about 15% of men fail to develop balding by age 70 and that these men show a strong paternal history of non-balding (RR 1.78). Analysis of the frequencies of balding in elderly fathers and brothers suggests that male pattern balding is an autosomal dominant trait. However, the low frequency of non-balding in elderly men meant that the numbers were too small to confirm the converse, i.e. that non-balding is a recessive characteristic. Family studies in women confirmed the paternal influence on balding in their brothers but there was little or no paternal contribution to female hair loss. In contrast, there was a strong maternal influence on hair loss in women but not in men. Female hair density showed a Gaussian distribution in the population indicating that it is a multifactorial trait.

These findings indicate that male and female patterns of balding are genetically different although there may be a ‘final common pathway’ of follicular senescence. If, as our results suggest, the predisposition to male balding is due to a single gene it may be more rewarding to study elderly men than young men with premature balding.