Genetic factors predispose to balding and non-balding in men

Male pattern balding is a common androgen-dependent trait. The frequency of balding in the population increases with age but not all men develop balding even in old age. It is well-known that balding tends to run in families but the nature of the underlying genetic predisposition and the mode of inheritance are unknown. In this study we examined scalp hair status across a wide age range in 572 men and took family histories of balding in first degree male relatives. The results confirmed that there is an increased frequency of balding in the fathers of young bald men and a high relative risk of balding in young subjects with a balding father but these effects declined with increasing subject age. In contrast, there was a pronounced increase in the frequency of non-balding in the fathers of non-bald elderly subjects and an increased relative risk of non-balding in elderly subjects with a non-bald father, which were not evident in younger subjects. Analysis of the frequencies of balding and non-balding in the brothers of balding and non-balding elderly men, categorised by paternal hair status, failed to show that either balding or non-balding is due to the action of a single gene. Nevertheless, our results indicate that there is a genetic influence on balding in young men and on non-balding in elderly men. It is possible that the same genes are responsible for determining predisposition to balding and to non-balding but, at this stage, we cannot assume that this is necessarily the case. Genetic analysis of balding in young men is complicated by the fact that the destiny of hair status in non-bald siblings is unknown. This difficulty is partly overcome by studying non-balding in elderly men where balding and non-balding in similarly aged siblings are more fully expressed, which may make this age group a better target for future studies in this field.