Figure 1: Continually high circulating levels of the stress related hormones, a peculiar feature of HF [A], induce decreases in intracellular Mg2+ [B], which may induce the progressive loss of ACs activity. The subsequent reduction in intracellular cAMP production and loss of circadian rhythm (LCR) [C], will lead to desensitization of β1-ARs [D] and heart failure development [E]. The treatment of these patients with diuretics increases the loss of magnesium, which could contribute significantly to maintaining the vicious circle and worsening of heart failure.