[Variations in the metabolism of lipoproteins as a function of thyroid hormones]

Like the demonstrated action of thyroid hormones on low density lipoproteins receptors and lipoproteins metabolism enzymes, plasma lipoprotein assays provide an insight into the classical variations of cholesterol blood levels observed in thyroid gland pathology. Thyroid hormones seem to play an important part in the regulation of lipid metabolism by accelerating the endogenous production of cholesterol as well as its penetration into cells. However, their most original effect consists of stimulation of tissue cholesterol removal, which may confer these hormones an anti-atherogenic property. The exact underlying mechanisms, notably their effect on the quantitative and qualitative distribution of apoproteins among lipoproteins, remain to be explored. Measurements of the cholesterol flows entering and leaving peripheral cells seem to provide a more accurate index than lipoprotein concentration to evaluate the actions of thyroid hormones, particularly those on atherogenesis.