Better understanding the role of the hormone, called Mullerian Inhibiting Substance (MIS), could also throw more light on the underlying biological mechanisms of some brain disorders, such as Alzheimer's disease, researchers believe.
"There are so many things to think about and dream about," Associate Prof Ian McLennan, of the Otago anatomy and structural biology department, said in an interview.
Many brain-related disorders were more common or more severe in one or other of the sexes, he said.
Females were more likely to develop anorexia and Alzheimer's, whereas attention deficit hyperactivity disorder, anti-social personality and motor neurone disease had a male bias.
Such sex-biases suggested subtle differences between the brains of males and females altered the course and/or presentation of brain diseases, he said.
The research could also help pave the way for potential new therapies.
The findings of Prof McLennan and fellow Otago neurobiologist Dr Kyoko Koishi have been published in the latest issue of the United States-based journal, Proceedings of the National Academy of Sciences.
They found male mice lacking MIS showed subtle changes in brain anatomy, and their behaviour was more akin to that of female mice.
In appearance and sexual behaviour, such male mice were typically male, but their nonreproductive behaviours were more feminine.
Male mice were known to explore a new environment more extensively than female mice, yet male mice with no MIS were significantly less inclined to explore.
Backed by a $750,000 Marsden Fund grant and an Otago Research Grant, Otago scientists have already started studying MIS in children.
They have recruited about 80 5- and 6-year-old children for the research, which involves a small blood test and some other fairly brief testing at the university.
Prof McLennan said scientists wanted to recruit more children, mostly male, and a member of the Otago research team, Dr Kirsty Morgan, of the Otago psychology department, could be contacted by e-mail: kmorgan@psy.otago.ac.nz
Scientists have been aware of MIS, which occurs only in males, for about 100 years, but Otago researchers have shown it has a much wider influence than previously thought.
