Prenatal steroid hormones in autism Aim of the project In 2015, the Autism Research Centre published a study that examined the concentrations of several prenatal steroid hormones in the amniotic fluid of males who were diagnosed with autism in Denmark and compared them to neurotypical controls (Baron-Cohen et al. 2015). Following principal component analysis, they found that a “steroidogenic” factor, derived out of all the assayed steroids, could explain most of the variance in autism likelihood. This factor was comprised from the concentrations of prenatal androgens such as androstenedione, testosterone, as well as other potent prenatal hormones, such as cortisol and progesterone. In 2019 they revisited the same cohort of individuals and examined every hormone separately, as well as a series of prenatal estrogens. Interestingly, univariate analyses revealed that the concentrations of estradiol, estrone and progesterone individually were the most predictive of autism likelihood (Baron-Cohen et al. 2019). However, it remains unclear whether these hormones have effects on brain development and are specific to the aetiology of autism. Furthermore, further research is required to elucidate the specific role of androgens, as their univariate associations with autism were marginal. Nevertheless, they may be important for their role in estrogen synthesis, as well as the masculinising properties of estrogens themselves. To complement and extend these findings to autistic females and to test for replication, researchers from the University of Cambridge propose a more detailed assessment of steroidogenesis in amniotic fluid of autistic females, as well as in new cohort of autistic males in Denmark. Importance of research Since amniocentesis is being replaced by nuchal translucency scans for screening, it is important to note that amniotic fluid samples will in the future be increasingly scarce. Given the recent findings of endocrine imbalance in autism (Cherskov et al. 2018; Baron-Cohen et al. 2019), the proposed studies can add important insight into the aetiology of autism, as well as provide potential avenues for earlier diagnosis and better treatments in cases of severe disability and comorbid conditions. Researchers involved Alex Tsompanidis Key findings This is a 10 month study starting in October 2019.