Renin gene expression is also regulated by circulating levels of free triiodothyronine (FT3) and free thyroxine (FT4) through beta-adrenergic activation; accordingly, the reduced sensitivity to beta-adrenergic stimulus occurring in hypothyroidism can cooperate with other hemodynamic abnormalities decreasing renin release (4, 5). This evidence concerns the gene REN and hypothyroidism.