'Sex-bias' hormone identified

Scientists have identified a hormone that could be responsible for non-reproductive differences in male and female brains.


The hormone, called Müllerian Inhibiting Substance (MIS), occurs only in men, and has previously been thought to have the sole function of preventing the formation of a uterus.

However, according to a new study of male and female mice, MIS may contribute to sex-linked behavioural traits that the researchers call 'sex-biases'.

"The sex-biases in the body do not define a person's sex or sexuality," explained neurobiologist Ian McLennan, who conducted the research at the University of Otago, New Zealand.

"Empathy, for example, has a female bias, but some of the greatest men are empathetic. Likewise, girls engage in less rough and tumble play than boys, but a boy who shuns rough and tumble play is still a boy," he said.

McLennan and his colleague Kyoko Koishi found most neurons in mice to have an MIS receptor. They then charted the behaviours of particular male and female mice that were missing either the gene for MIS or its receptor.

Male mice missing either of these showed a feminisation of some behavioral traits. The researchers noted differences in the 'male tendency' to explore and spatial processing.

Further work is needed to determine which human traits are regulated by MIS; however, the researchers hope that their findings contribute towards a greater understanding of human diversity.

More information is available from the University of Otago's press release.