Twin study: genotype-dependent epigenetic factors affecting free thyroxine levels in the normal range

Area of Science:

• Endocrinology
• Epigenetics
• Genetics

Background:

• Thyroid function is crucial for overall health.
• DNA methylation plays a role in gene regulation.
• Understanding factors affecting thyroid hormones like free thyroxine (FT4) and thyroid-stimulating hormone (TSH) is clinically important.

Purpose of the Study:

• To investigate the association between DNA methylation and thyroid function markers (FT4 and TSH).
• To explore the interplay of DNA methylation, genetic polymorphisms, and thyroid hormone levels in monozygotic twins.

Main Methods:

• Epigenome-wide association studies (EWAS) were conducted on monozygotic twin pairs discordant for FT4 or TSH levels.
• Analysis focused on the relationship between within-pair differences in hormone levels and DNA methylation.
• The influence of genetic polymorphisms on methylation sensitivity was also assessed.

Main Results:

• Two CpG sites were found to be significantly associated with FT4 levels.
• Significant differences in DNA methylation levels were observed within FT4-discordant pairs, linked to polymorphisms in the EPHB2 gene.

Conclusions:

• FT4 levels may be influenced by a combined effect of DNA methylation and genetic polymorphisms within the EPHB2 gene.
• This suggests a potential epigenetic and genetic mechanism regulating thyroid hormone levels.