New research shows that girls with higher testosterone levels at birth are more likely to show signs associated with autism such as poor communication skills and social difficulties at age 10.
The findings lend support to an emerging theory of how autism develops. It is proposed that greater exposure to testosterone during pregnancy and early childhood leads to an extreme form of typical male brain development. As well as fitting with the signs of autism this may explain why more boys than girls are affected by the developmental disorder.
The research was carried out in Australia by Dr. Andrew Whitehouse, a research fellow at the Telethon Institute for Child Health Research in Perth. The results of the study are published this month's edition of the journal Psychoneuroendocrinology.
Dr. Whitehouse studied 78 girls from a larger group of 2000 from West Australia whose mothers were asked to participate while pregnant, and whose health and development has been followed up at multiple intervals. The 78 girls ultimately included in the study represent the largest group of children ever investigated for the link between testosterone levels at birth and communication and social skill development. No previous study has followed children until such an advanced age either - an important factor when one considers that subtle social and communication problems may not be apparent in infants and young children.
The girls in the study were assessed for their level of testosterone exposure while in the womb by measuring testosterone levels in umblilical cord blood collected and stored when they were born. Those with the highest exposures to testosterone were more likely to show deficiencies in female traits typically considered positive, such as empathy and social awareness. Dr. Whitehouse explains that these girls either talked too little or too much - both signs of impaired social development.
Interestingly however the same girls did not show more signs of typically male traits considered positive, such as spatial awareness and problem-solving ability, compared to girls with lower testosterone exposure.
Dr. Whitehouse, a psychologist and autism specialist, suggests interventions such as drugs aimed at altering the balance of hormones could be used in high-risk pregnancies if excessive testosterone exposure before birth is proven by future studies to adversely affect child development.
There are a number of reasons why some women may have higher levels of testosterone than others including individual genetic variability, age (the 30s being a troublesome time), hormonal disorders - particularly those affecting the ovaries and/or adrenal glands (the most common being polycystic ovarian syndrome (PCOS)), and the use of steroid medications and other drugs such as Phenytoin (Dilantin) which is used to treat epilepsy. Environmental pollutants may also cause hormonal imbalances but the research is still unclear regarding testosterone.
Dr. Whitehouse conceded testosterone measurements taken from umbilical cord blood at birth might not be representative of mid-pregnancy levels, when brain development is at a critical stage. However, he said measurements of amniotic fluid, used by British scientists who have also linked male hormones to autistic behaviours, were potentially even less useful as it is usually only older mothers who undergo the amniocentesis test.
Dr. Whitehouse said the so-called ''extreme male-brain'' theory of autism was attractive because, ''there aren't too many actual biological theories this ties in most of the behaviours we see.'' He is now seeking funding to continue his studies on the entire 2000 strong West Australia cohort, including boys, to definitively determine the role of testosterone in autism.