In a new study, published in Borderline Personality Disorder and Emotion Dysregulation, Springer Nature, researchers from Queen Mary University of London investigate the association between genetics, thyroid function, and mental health disorders.
Thyroid gland
Evidence from genetic studies shows a possible overlap between borderline personality disorder (BPD) and schizophrenia (SCZ). Yet, the exact nature of the role of thyroid function, particularly in terms of causality, in these mental disorders, remains unclear. To address this gap, a team of scientists at Queen Mary University of London investigated the potential of casual associations through Mendelian Randomisation genetic studies.
The study investigated whether genetic variations associated with thyroid function, such as levels of thyroid-stimulating hormone (TSH) and free thyroxine (FT4), or the presence of hypothyroidism, are linked to the risk of developing BPD or SCZ. Additionally, researchers explored the reverse causal associations, examining whether genetic predisposition to BPD or SCZ have a causal effect on thyroid dysfunction.
Initial findings suggested a potential causal link between FT4 levels and BPD or SCZ, primarily attributed to genetic changes in the LHX3 and DIO1 genes. LHX3 is known to play a crucial role in the expression of genes implicated in pituitary gland and nervous system development, as well as associations with sex hormones such as testosterone. The protein encoded by the DIO1 gene is essential for the production of the thyroid hormone, Triiodothyronine (T3), which is crucial for growth.
However, further analysis revealed that these genetic variants may exert their effects through complex mechanisms potentially unrelated to direct thyroid hormone regulation. Upon excluding variants in the LHX3 and DIO1 genes, the researchers found no evidence for a causal relationship between thyroid function and BPD or SCZ.
Dr Eirini Marouli, lead study author and Reader in Computational Biology at Queen Mary University of London’s William Harvey Research Institute said: “It is important to understand the underlying mechanisms through which changes in our DNA related to thyroid function could potentially affect BPD or SCZ risk, any reverse causal associations, along with pathways not directly driven by thyroid function. In addition, other non-genetic effects, such as lifestyle and development, might be involved in the presence of thyroid dysfunction, BPD or SCZ in the population."
“This study has potential implications in evaluating treatment options for individuals presenting with symptoms of thyroid dysfunction, BPD or SCZ along with personalised medicine.”
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