NCX1 (Na(+)/Ca(2+) exchanger (NCX-1)) expression and protein levels vary during heart development and in response to changes in thyroid hormone levels (1). The expression of the NCX1 gene is two-fold higher in the hearts of fetal versus adult mice. In addition, NCX1 mRNA and protein levels were upregulated in hypothyroidic hearts. In hyperthyroidic hearts this response was reversed, however.
