Saturday, May 19, 2012

Validating the Extreme Male Brain Theory of Autism

According to an abstract published for IMFAR 2012, it looks like Simon Baron-Cohen has finally gotten around to actually testing the core idea of his extreme male brain theory of autism.  The core idea being that children who go on to develop autism are exposed to a higher than normal level of prenatal testosterone.

To do so, the good doctor actually measured the level of four sex hormones (progesterone, 17a-hydroxyprogesterone, androstenedione, and testosterone) and cortisol in the amniotic fluid of 62 males with autism and 231 males without autism that had been preserved as part of the Danish Historic Birth Cohort.

The results of this analysis, although preliminary, are quite surprising.  The autism group did show an increased level of testosterone, that much was predicted by the theory.  But what was not expected was that the autism group also showed an increased level of the other three sex hormones as well.  The levels of cortisol were the same between the autism and control groups.

On a trivial level, this result calls into question the core idea of extreme male brain theory of autism because it isn't just testosterone that is out of balance, it is other sex hormones as well (i.e. testosterone and estrogen would likely both be out of balance).

On a non-trivial level, this result shows that far more than just sex hormones are out of balance.  These four  hormones are involved in other biological processes as well.  Wikipedia has a nice picture of how these hormones fit together -

The biology is a little beyond me, but notice cortisol hanging out on the right side of the picture?  I have to wonder how you can push several parts of the process without impacting one of the end results of the pathway.

Regardless, from what I understand, these four hormones are tied to the CYP17A1 pathway and this pathway is involved in a whole lot of other things.  These things include the oxidation of organic substances, metabolism of drugs and other toxic chemicals, and the synthesis of cholesterol, steroids, and other lipids.

Notice anything familiar on that list?  Here a hint, all of these things have been tied to autism or found to be out of balance in some people with autism.

So, what do you think happens to a developing fetus when an important biological pathway like this is pushed out of balance?  I don't understand the biology well enough to fully grasp the consequences but I don't think it can be anything good.

Many of the body's systems are are cross linked and when you push one of them out of balance you are going to unbalance other parts as well.  And if there is one common theme that ties together all of the many abnormal biological findings in autism, it is a tendency to be out of balance and at one extreme or the other.

Of course, these results are preliminary and need to be replicated by other groups.  The findings also need to be replicated in the general autism population.  The current paper, like so many of Simon Baron-Cohen's papers, focuses exclusively on the high functioning males with autism.  It excluded anyone with autism who had intellectual disability and anyone who was female.

These result also beg the question of why all of these hormones are out balance in the first place.  Something has to be pushing these hormones out of balance in either the mother or fetus (and please don't say "it's genetic").  It is a good thing that endocrine disruptors such as Bisphenol A aren't becoming more widespread and aren't being found in high levels in pregnant women or I might be worried.

And, almost without a doubt, the "autistic rights" movement is going to have a conniption about these results.  Instead of focusing on the fact that results like this help us to better understand the biology of autism and to come up with better ways of helping people with autism, I can almost guarantee that they are going to focus on the idea that this result might lead to a prenatal test for autism.

The summary of the paper is available from the IMFAR 2012 site and I am including it below.

S. Baron-Cohen, B. Auyeung1, B. Nørgaard-Pedersen2, D. M. Hougaard2, M. W. Abdallah2,3, L. Melgard2, A. Cohen2, L. Ruta1 and M. V. Lombardo1, (1)Autism Research Centre, University of Cambridge, Cambridge, United Kingdom, (2)Department of Clinical Biochemistry and Immunology, Statens Serum Institute, Copenhagen, Denmark, (3)Department of Epidemiology, Aarhus University Faculty of Health Sciences, Aarhus C, Denmark

Background: Autism Spectrum Conditions (ASC) are much more common in males. One hypothesized biological mechanism that could potentially influence this male bias is fetal testosterone (FT) or more generally the broader steroidogenic pathway leading to the synthesis of testosterone (Baron-Cohen et al 2011, PLOS-Biology; Baron-Cohen et al, 2005, Science). Sex steroids are well established as an epigenetic fetal mechanism for modifying gene expression and a host of other molecular/cellular factors in early brain development and may be helpful as predictive markers for those who may be at increased risk for later diagnosis.

Objectives: To test for the first time the hypothesis that fetal steroidogenic activity is elevated in individuals who later receive a diagnosis of ASC.

Methods: 62 male cases of classic autism (without a comorbid diagnosis of ’mental retardation’) or Asperger Syndrome and 231 typical male controls were selected from the Historic Birth Cohort, a biobank of amniocentesis samples taken from the Danish population since 1993. Using mass spectrometry we assessed the concentration of 4 hormones in the ?4 steroidogenic pathway tied explicitly to CYP17 enzymatic pathway (i.e. progesterone, 17a-hydroxyprogesterone, androstenedione, and testosterone) in amniotic fluid sampled during weeks 10-20 of gestation. Cortisol was also measured as a control hormone that is not within the main ?4 sex steroid biosynthesis pathway. Analysis of the main hypothesis (that ?4 pathway hormones are elevated in ASC) consisted of computing the multivariate Wilk’s lambda statistic within a permutation test (re-computed over 1,000,001 iterations). Further classification analyses were implemented using logistic regression and classification performance measures were compared to null distributions estimated under chance conditions via permutation tests.

Results: A permutation test (1,000,001 iterations) on the multivariate Wilk’s lambda statistic showed that when testing all hormones there was an overall group difference in the direction of ASC>Control (p=0.01). Following up this multivariate result with tests on each hormone individually, we found that concentration of all 4 steroidogenic hormones in the ?4 pathway were elevated in the ASC group, but there was no between-group difference in cortisol concentration. Logistic regression was then used to classify diagnostic status using all hormones. Classification accuracy, specificity, PPV, and NPV were all significantly higher than chance values estimated by permutation tests (all p<0.02). Sensitivity approached statistical significance (p=0.06).

Conclusions: This work represents the first direct verification that fetal exposure to sex steroids is elevated in those who later receive a diagnosis of autism. Given the role of sex steroids in a host of interactions at the genetic and molecular/cellular level, this finding represents an important breakthrough in understanding early factors that contribute to the pathophysiology of ASC. Classification analyses show that while these markers are statistically significant in predicting later diagnosis status, such markers should not be used as a fetal test. Future work comparing autism to other neurodevelopmental conditions will be important in clarifying the specificity of such markers to autism, and how such fetal hormones impact the neurodevelopment of autism.

Thursday, May 17, 2012

Study : Global Prevalence of Autism and Other Pervasive Developmental Disorders.

I am constantly amazed that otherwise rational people can look at the steady upward march of autism prevalence numbers and confidently state that it isn't real.  Certain researchers seem to always pull out the better awareness, broadening criteria, diagnostic substitution, and availability of services arguments to explain away any increases without ever taking the time to empirically demonstrate that these factors are actually responsible for the increase.

It might be just me, but if you are going to put forth a theory then you had best have evidence to support that that theory.  Otherwise your theories are just speculation and are no better than all of the other unsupported ideas surrounding autism, such as the extreme male brain theory of autism.

I haven't read the full text of this recent paper on global prevalence (abstract below), but from the abstract it seems to yet another "the sky isn't falling, we are just better at seeing it" type of paper.  Which, in light of all the recent research into autism prevalence and causes, just seems badly out of touch.

I have to wonder at what point the epidemic denialists will stop pulling out the same tired reasons to keep explain away the ever increasing number of people with autism.  As worldwide autism rates go from well under 1% to Korea style over 2% and beyond, at exactly what point will the denialists stop using the exact same theories to explain each and every increase?  How many times can the spectrum double before these reasons start to sound just like excuses?

Are we really going to have to wait for the sky to finish falling and literally hit them in the face before they will admit that there is in fact a problem?

Global Prevalence of Autism and Other Pervasive Developmental Disorders.

Elsabbagh M, Divan G, Koh YJ, Kim YS, Kauchali S, Marcín C, Montiel-Nava C, Patel V, Paula CS, Wang C, Yasamy MT, Fombonne E.

We provide a systematic review of epidemiological surveys of autistic disorder and pervasive developmental disorders (PDDs) worldwide. A secondary aim was to consider the possible impact of geographic, cultural/ethnic, and socioeconomic factors on prevalence estimates and on clinical presentation of PDD. Based on the evidence reviewed, the median of prevalence estimates of autism spectrum disorders was 62/10,000. While existing estimates are variable, the evidence reviewed does not support differences in PDD prevalence by geographic region nor of a strong impact of ethnic/cultural or socioeconomic factors. However, power to detect such effects is seriously limited in existing data sets, particularly in low-income countries. While it is clear that prevalence estimates have increased over time and these vary in different neighboring and distant regions, these findings most likely represent broadening of the diagnostic concets, diagnostic switching from other developmental disabilities to PDD, service availability, and awareness of autistic spectrum disorders in both the lay and professional public. The lack of evidence from the majority of the world's population suggests a critical need for further research and capacity building in low- and middle-income countries. Autism Res 2012

PMID: 22495912 DOI: 10.1002/aur.239

Sunday, May 13, 2012

Study : A common X-linked inborn error of carnitine biosynthesis may be a risk factor for nondysmorphic autism.

It isn't often that I read a paper on autism that presents a complete picture of what autism might be (for some people) from genetic cause to biological pathways to possible treatment.  But a paper on an inborn error of carnitine biosynthesis from last week might fit the bill.

This paper ties together a genetic mutation, the effect of the mutation on the body's biological pathways, possible dietary factors in early childhood, and hints at a possible way to treat existing autism or to decrease the risk of autism developing in the first place.

The abstract is below and, if you are interested, the study text is open access and available here.

A common X-linked inborn error of carnitine biosynthesis may be a risk factor fornondysmorphic autism.

We recently reported a deletion of exon 2 of the trimethyllysine hydroxylase epsilon (TMLHE) gene in a proband with autism. TMLHE maps to the X chromosome and encodes the first enzyme in carnitine biosynthesis, 6-N-trimethyllysine dioxygenase. Deletion of exon 2 of TMLHE causes enzyme deficiency, resulting in increased substrate concentration (6-N-trimethyllysine) and decreased product levels (3-hydroxy-6-N-trimethyllysine and ?-butyrobetaine) in plasma and urine. TMLHE deficiency is common in control males (24 in 8,787 or 1 in 366) and was not significantly increased in frequency in probands from simplex autism families (9  in 2,904 or 1 in 323). However, it was 2.82-fold more frequent in probands from male-male multiplex autism families compared with controls (7 in 909 or 1 in 130; P = 0.023). Additionally, six of seven autistic male siblings of probands in male-male multiplex families had the deletion, suggesting that TMLHE deficiency is a risk factor for autism (metaanalysis Z-score = 2.90 and P = 0.0037), although with low penetrance (2-4%). These data suggest that dysregulation of carnitine metabolism may be important in nondysmorphic autism; that abnormalities of carnitine intake, loss, transport, or synthesis may be important in a larger fraction of nondysmorphic autism cases; and that the carnitine pathway may provide a novel target for therapy or prevention of autism.


Celestino-Soper PB, Violante S, Crawford EL, Luo R, Lionel AC, Delaby E, Cai G, Sadikovic B, Lee K, Lo C, Gao K, Person RE, Moss TJ, German JR, Huang N, Shinawi M, Treadwell-Deering D, Szatmari P, Roberts W, Fernandez B, Schroer RJ, Stevenson RE, Buxbaum JD, Betancur C, Scherer SW, Sanders SJ, Geschwind DH, Sutcliffe JS, Hurles ME, Wanders RJ, Shaw CA, Leal SM, Cook EH Jr, Goin-Kochel RP, Vaz FM, Beaudet AL. A common X-linked inborn error of carnitine biosynthesis  may be a risk factor for nondysmorphic autism. Proc Natl Acad Sci U S A. 2012 May 7. [Epub ahead of print]
PubMed PMID: 22566635.