1. In utero estrogen exposure & increased risk of Autism Spectrum Disorder (ASD): The potential epigenetic links between maternal hormone profile, maternal health exposure and the elevated risk of giving birth to an autistic child
Geoffrey A. Bocobo ’16 (Honors Thesis Advisor: Molly Helt, Ph.D.) Neuroscience Program, Trinity College, Hartford, Connecticut 06106
Introduction
Rates of ASD are on the rise (CDC, 2015)- 600% increase
Cannot be fully explained by a change in diagnostic criteria
Genetic research is very non-specific (~700 genes, fragile X)
In Utero Environment
The Extreme Male Brain Theory of Autism (Baron-Cohen, 2006)
Neuro-hormone qualities  mediates brain development, lipophilic nature = epigenetic effects
Maternal & fetal hormone levels possess moderate correlations with each other (Troisi et al., 2003)
Unrelated studies in opposition to androgen theory
Higher incidences of hyperthyroidism & breast cancer (Mouridsen et al., 2009), early age of menarche, high BMI (Lyall et al., 2011) and exposure to synthetic estrogen & endocrine mimckers (Zachor et al. 2010) all associated with higher rates of autism
These conditions are also caused by or cause increased maternal estrogen levels.
Therefore, increased maternal estrogen levels, and thus, fetal exposure to estrogen may constitute a risk factor for giving birth to a child with autism.
Materials and methods
PARTICIPATION
Mothers of ASD children & mothers of non-ASD children participated in an online survey
253 were mothers of typically developing children
232 were mothers of children with autism
Fathers & non-biological mothers were excluded from the study (variable of interest is in-utero exposure to estrogen)
Recruitment done through CT Listservs & aimed at parents with children who have ASD or a child with special needs
Each mother recruited a friend or neighbor to serve as their control
MATERIALS
Survey required checking of boxes or brief responses
Demographical information
Age of mother/child, number of children, gender, educational background, employment status, developmental outcomes of the child, etc
Indicators of maternal estrogen dominance
Menstrual cycles, contraceptive use, history of hormone related medications, BMI, exogenous exposures, etc.
PROCEDURE
Approved by Institutional Review Board: Trinity College
Mothers accessed a link with a statement about the purpose and length of the study
Consent was implied by continuing on with the survey
DATA
Results
χ(1) = 5.067, p =0.24
χ(1) = 4.674, p = 0.31
t(461) = -2.89, p = 0.04
t(468) = 4.175, p < .0001
Discussion
Compared with controls, the group of mothers of children with ASD showed higher incidences of breast cancer, χ(1) = 5.067, p =0.24, a condition associated with high levels of endogenous estrogen, and lower incidences of hyperthyroidism, χ(1) = 4.674, p = 0.31, a condition associated with lower levels of endogenous estrogen. In addition, mothers of children with autism reported both a higher body mass index by age 18, t(461) = -2.89, p = 0.04, and a younger age at menarche, t(468) = 4.175, p < .0001, both of which are consistent with greater lifetime exposure to estrogen compared with mothers of typically developing children. This study necessitates replication using a significantly larger sample size before definitive conclusions may be drawn. However, these results certainly warrant further investigation into our hypothesis and many mechanisms of action exist that can be explanatory of this phenomenon (if future research sees this estrogen theory of autism to be true).
Epigenetic disruptions may occur within the developing fetus due to high in-utero estrogen levels, which could increase the risk of the a child later developing ASD. Given the expansion of the endocrine mimicking chemicals in the environment in recent decades, could changing maternal hormones be part of the reason for ASD being on the rise? If so, and if fetal brain development is adversely affected by gestational exposure to high levels of estrogen, it is possible that mothers could potentially change their health habits to lower their risk of having a child with ASD.
Figure 6. Incidence of breast cancer in mothers of ASD children vs. in mothers of typically developing children
Figure 7. Incidence of hyperthyroidism in mothers of ASD children vs. in mothers of typically developing children
Figure 1. All of the risk genes associated with Autism Spectrum Disorder. Taken from: autism.org.uk
Figure 2. The increase in rates of Autism Spectrum Disorder in the past 40 years.
Taken from: autismspeaks.org
Figure 8. Average age of Menarche in mothers of ASD children vs. in mothers of typically developing children
Figure 9. Average BMI by age 18 in mothers of ASD children vs. in mothers of typically developing children
Figure 3. All data was analyzed using SPSS software. Taken from ibm.spss.com
Figure 4. All categorical data from the questionnaire analyzed using chi-square analysis
Figure 5. The variance and trends of the non-categorical data was analyzed via T-Tests
Figure 10. A developing fetus. Taken from webmd.com
Works Cited
I would like to thank Professor Helt for providing me with an opportunity to complete a senior thesis, despite not having much research experience under my belt at the time. I would also like to show my appreciation for all those involved with the Neuroscience Program at Trinity. Thank you for offering such a wonderful major, not to mention planning an amazing 25th year anniversary.
Acknowledgments
For Further Information
Cheslack-Postava, K et al., (2011) Closely Spaced Pregnancies are associated with increased odds of Autism in California Sibling Births. Pediatrics, 127(2),
Cohen, Baron et al., (1999) The Extreme Male Brain Theory of Autism. Neurodevelopmental Disorders, 1,
Funderbunk, SJ et al. (1983) Parents Reproductive Problems and Gestational Hormonal Exposure in Autistic and Schizophrenic Children. Journal of Autism and Developmental Disorders, 13(3),
Knickmeyer, Rebecca et al., (2007) Age of Menarche in Females with Autism Spectrum Conditions. Developmental Medicine and Child Neurology, 48(12),
Lyall, Kristen et al., (2011) Maternal Early Life Factors Associated with Hormone Levels and the Risk of Having a Child with an Autism Spectrum Disorder in the Nurses Health Study II. Journal of ASD and Developmental Disorders, 41(5),
Mouridsen, Svend Erik et al., (2009) Sibling Sex Ratio of Individuals Diagnosed with Autism Spectrum Disorder as Children. Developmental Medicine and Child Neurology, 52(3),
Trowoger, Shelley et al., (2006) Intake of Folate and Related Nutrients in Relation to Risk of Epithelial Ovarian Cancer. American Journal of Epidemiology, 163(12),
Wilkerson, DS et al., (2002) Perinatal Complications as Predictors of Infantile Autism. International Journal for Neuroscience, 112(9),
Zachor, Lahat, & Itzchak (2010) IVF and prematurity are prenatal risk factors associated with Autism Spectrum Disorder but not with Autism severity. Presented at the Ninth Annual International Meeting for Autism Research (IMFAR).
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