RBM20 and thyroid gland disorder: In this study, we investigated RBM20 expression levels and RBM20-mediated pre-mRNA splicing regulated by hormones (thyroid and insulin) in fast and slow muscle types, and also determined whether thyroid hormone modulates the RBM20-mediated pre-mRNA splicing via the genomic or non-genomic signaling pathways in differentiated and undifferentiated muscle myoblasts (C2C12 cells).