Bidirectional association between hypothyroidism and myasthenia gravis: a Mendelian randomized study

Area of Science:

• Endocrinology
• Neurology
• Genetics

Background:

• Observational studies suggest a link between hypothyroidism and myasthenia gravis (MG).
• A causal relationship between hypothyroidism and MG has not been definitively established.
• Mendelian randomization (MR) offers a robust method to investigate causal associations.

Purpose of the Study:

• To investigate the potential causal association between hypothyroidism and myasthenia gravis (MG).
• To leverage genetic data for a two-sample Mendelian randomization study.
• To determine if hypothyroidism is a risk factor for developing MG.

Main Methods:

• Utilized summary statistics from large genome-wide association studies (GWAS) for hypothyroidism and MG.
• Selected single-nucleotide polymorphisms (SNPs) as genetic instrumental variables, ensuring no linkage disequilibrium and statistical significance.
• Employed inverse variance weighted (IVW), weighted median, and MR-Egger methods for causal inference, with sensitivity analyses including heterogeneity and pleiotropy tests.

Main Results:

• Genetic liability to hypothyroidism was significantly associated with an increased risk of MG (IVW, OR: 1.36, p=7.53×10⁻⁵).
• Results were consistent across different MR methods and supported by an independent validation dataset.
• Bidirectional MR analysis indicated no evidence of reverse causality from MG to hypothyroidism.

Conclusions:

• This Mendelian randomization study provides evidence that hypothyroidism causally increases the risk of myasthenia gravis (MG).
• Further research into the underlying biological mechanisms is warranted.
• Understanding this causal link may lead to novel therapeutic strategies for MG.