Monday 2 September 2013

Induced labour, maternal thyroid hormone and autism

The BBC TV program 'The Nine Months That Made You' was a particularly interesting eye-opener for me. Not only did it introduce the work of David Barker (see this post) and his very thoughtful hypothesis but also stressed how environmental factors during those early months (and perhaps even before we were glints in our parents' eyes) might have potentially far-reaching effects on how we live our lives.

With the early months in mind, I'm introducing two pieces of research which have been (fairly) recently doin' the rounds. The first is the paper by Simon Gregory and colleagues* who suggested that there may be a correlation between the medical induction of labour and an elevated risk of offspring autism. You can also see some media coverage of this paper here and some rather more critical discussion here. The second paper is by Gustavo Román and colleagues** who again with the correlation machine in full working order suggested that the risk of offspring autism was greater for those mothers who were deficient in thyroid hormone. Again, some coverage can be viewed here.

I'm not on this occasion going to focus too much on the Gregory paper because others have done a far better job than I could. I was interested in two points raised in the article though: (a) that males seemed to show more of an 'association' between such birthing interventions and subsequent risk - think fragile male for example, and (b) that we are presented with a slightly different viewpoint about the potential value of the 'cuddle hormone', oxytocin. Indeed this potentially more ominous side to oxytocin is something that has been discussed previously in the scientific literature (see here).

The Román paper on maternal hypothyroxinemia - low levels of thyroid functioning - and offspring autism risk is an interesting one. A couple of years back I wrote a post on autism and the thyroid (see here). At that time (2011) there was only a limited published research base on how the thyroid hormones and its functions 'might' be linked to autism, but that's not to say it hadn't been mentioned (see this paper***). The difference with the Román paper was the focus on maternal thyroid function in line with other reports that hypothyroxinemia in pregnancy might not be particularly desirable for later offspring outcomes (see this paper**** open-access for example).

Based on quite a large initial sample of over 5000 women taking part in the Generation R Study in the Netherlands (which itself has produced some interesting work), Román et al. looked at various aspects of thyroid function during early-middle pregnancy. They specifically focused on severe maternal hypothyroxinemia. A number of years later, mums (and dads) then completed various measures of behavioural functioning for offspring from which authors derived "a probable autistic child". The results suggested that where severe maternal hypothyroxinemia (n=136) was present, the odds ratio for having a 'probable' child with autism was significantly elevated.

I probably don't need to point out why I have highlighted the word 'probable' in the above paragraph. The fact that the authors relied on parental report of one of the sub scales of the Child Behavior Checklist "and/or" the Social Responsiveness Scale could be construed as at odds with the title of the behaviour which specifically talks about "increased autism risk" over and above what they were actually looking at: "autistic symptoms". You might think I am just nit-picking about this but certainly I wouldn't want anyone to think that diagnosing an autism spectrum conditions is as easy as just filling out a short questionnaire. Screening and part of the assessment procedure... yes, diagnosis... no.

That all being said I remain interested in the findings and wisely how the authors stress that their findings "cannot establish causality" That and the fact that Román has previously published on some interesting ideas to account for thyroid issues in relation to autism***** means that science has a few more avenues to look at to potentially account for their findings (see here too).

Music maestro please. How about Blur with Girls and Boys?


* Gregory SG. et al. Association of Autism With Induced or Augmented Childbirth in North Carolina Birth Record (1990-1998) and Education Research (1997-2007) Databases. JAMA Pediatr. 2013 Aug 12. doi: 10.1001/jamapediatrics.2013.2904.

** Román GC. et al. Association of gestational maternal hypothyroxinemia and increased autism risk. Ann Neurol. 2013 Aug 13. doi: 10.1002/ana.23976.

*** Hoshiko S. et al. Are thyroid hormone concentrations at birth associated with subsequent autism diagnosis? Autism Res. 2011 Dec;4(6):456-63. doi: 10.1002/aur.219.

**** Negro R. et al. Hypothyoxinemia and pregnancy. Endocr Pract. 2011 May-Jun; 17(3): 422–429.

***** Román GC. Autism: transient in utero hypothyroxinemia related to maternal flavonoid ingestion during pregnancy and to other environmental antithyroid agents. J Neurol Sci. 2007 Nov 15;262(1-2):15-26.

---------- Gregory SG, Anthopolos R, Osgood CE, Grotegut CA, & Miranda ML (2013). Association of Autism With Induced or Augmented Childbirth in North Carolina Birth Record (1990-1998) and Education Research (1997-2007) Databases. JAMA pediatrics PMID: 23938610 Román GC, Ghassabian A, Bongers-Schokking JJ, Jaddoe VW, Hofman A, de Rijke YB, Verhulst FC, & Tiemeier H (2013). Association of gestational maternal hypothyroxinemia and increased autism risk. Annals of neurology PMID: 23943579

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