Increased blood levels of cholesterol that are seen in hypothyroidism are most likely due to
Thyroid hormones induce the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, which is the first step in cholesterol biosynthesis.Moreover, triiodothyronine (T3) upregulates LDL receptors by controlling the LDL receptor gene activation. This T3-mediated gene activation is done by the direct binding of T3 to specific thyroid hormone-responsive elementsFuhermore, T3 controls the sterol regulatory element-binding protein-2 (SREBP-2), which in turn regulates LDL receptor's gene expression Ref: DM Vasudevan, 7th edition, page no: 336, 334, 676
Decreased calorigenesis
Decreased production of LDL receptor in liver and the thus decreased clearance by liver
Decreased production of LDL receptor in the adipose tissue and increases release of cholesterol from adipose tissues
Increased breakdown of lipoproteins releasing releasing cholesterol in circulation
Endocrinology