Thyroid-stimulating hormone (TSH) has been shown to stimulate cholesterol synthesis in liver. Zhang et al, in J. Lipid Res. (2105) 56, 963–971 investigated the mechanism of this effect by treating mouse hepatocytes (liver cells) with TSH. The data below show the ratio of phosphorylated HMG-CoA reductase to total HMG-CoA reductase in these cells following treatment with 0, 1, or 4 mM bovine TSH (bTSH). Based on these data and your knowledge of the regulation of HMG-CoA reductase, propose a mechanism that explains the stimulatory effect of TSH on cholesterol synthesis. 

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bTSH (μm) Phosphorylated/total HM GCR (fold) 0.0 0.5 H* 4 * 1.0 1.5