Steroid hormone pathways, vitamin D and autism: a systematic review.

This review looked at whether hormone levels during pregnancy might help explain why autism is more common in boys. Researchers examined 22 studies about pregnancy hormones, vitamin D levels, and a condition called hyperandrogenemia (high male hormones) in mothers. They found some interesting connections between these factors and autism, but the results were complicated and not definitive. More research is needed to understand how pregnancy hormones might affect a baby's brain development.

This systematic review examined whether prenatal steroid hormones and vitamin D levels contribute to autism development, particularly the higher occurrence in males. The review analyzed 22 studies investigating three areas: steroid hormone levels in the fetal environment, maternal and fetal vitamin D levels during pregnancy, and maternal hyperandrogenemia before pregnancy. Results showed promising but complex relationships between steroid metabolism and autism. However, findings were limited by observational study designs, insufficient examination of sex differences, inadequate control for confounding factors, and unclear timing effects of hormone exposure on fetal brain development.

The evidence suggests potential mechanistic pathways but requires more rigorous research.

While promising biological pathways are suggested, current evidence is insufficient to guide clinical practice. Research highlights the need for better understanding of prenatal factors in autism development, particularly hormonal influences that may explain sex differences in autism prevalence.

Mostly observational study designs limit causal inferences. Insufficient investigation of sex-specific effects, inadequate control for confounding factors, and unclear timing of hormone exposure effects on fetal neurodevelopment. Small number of studies in each category examined.

The origins of the male preponderance in autism incidence remain unclear. The idea that perinatal factors associated with sex differentiation (e.g., steroid hormone pathways) may increase the possibility of the emergence of autism is complementary to the hypothesis that female individuals are intrinsically less likely to develop autism. Empirical evidence for the mechanistic roles of in utero steroid hormones in autism etiology is accumulating but inconsistent. We conducted a systematic review using rigorous criteria for the measurements of steroids and vitamin D exposure, to summarize the potential contributing roles of prenatal and early postnatal steroids and vitamin D alterations to the emergence of autism.

We searched PubMed, PsychInfo, Scopus, and included 22 studies for qualitative synthesis. Among them, six studies examined the association of autism diagnoses in offspring and levels of steroids and precursor steroid hormones in the fetal environment, eight studies examined the associations between autism and maternal and fetal blood vitamin D levels during pregnancy and at birth, and eight studies examined the associations between offspring autism diagnoses and maternal hyperandrogenemia diagnosed before pregnancy. We identified promising and complex results regarding the relations between steroid metabolism and autism. The interpretation of findings was limited by the mostly observational study designs, insufficient investigation of the effects of offspring sex, confounders and their cumulative effects on the development of the child, and unclear impact of the timing of steroids exposure and their effects on fetal neurodevelopment.