Hypothyroidism on lipid metabolism

CORIA M, CARMONA Y. OLIVEROS L., GIMÉNEZ M

Hypothyroidism- Influences and Treatments

INTECH

Año: 2012; p. 1 - 348

Hypotyroidism and lipid metabolism It has long been known that T3 plays a critical role in lipid metabolism by regulating genes involved in lipogenesis and lipolysis. The underlying mechanisms, however, have only begun to be unraveled in recent years. Thyroid hormones are of vital importance in maintaining the initial level of phospholipids in cell membranes and fatty acids composition of the lipids .Hypothyroidism, characterized by low serum thyroid hormone levels, is associated with reduced metabolism, reduced lipolysis, weight gain, reduced cholesterol clearance, and elevated serum cholesterol. It is known that thyroid hormone has genomic and no genomic effects. Nuclear mechanisms of thyroid hormone action have been extensively described , but an increasing number of nogenomic effects of the hormone at the cellular level have been recognized in the past 10 years . Nongenomic actions of thyroid hormone are by definition independent on nuclear receptors for the hormone and have been described at the plasma membrane, various organelles, the cytoskeleton, and in cytoplasm. The actions include alterations in transport of Ca+2, Na+ and glucose; changes in activities of several kinases, including protein kinase C (PKC), cAMP -dependent protein kinase and mitogen -activated protein kinase. Iodothyronines also can regulate nongenomically through a PKC activation of neutral lipids, phospholipids and phosphatidylinositol 4,5- bisphosphate (PtdIns (4,5)P2) Thyroid hormone receptors (TRs) also possess two isoforms, TR-α and -β (Nr1a1 and Nr1a2), and each isoform exists as two or three subtypes, respectively (α1, α 2, β1, β2, and β3) TR- α plays a key role in postnatal development, adipose tissue and cardiac metabolism, whereas TR-β regulates multiple steps in hepatic metabolism as well as thyroid hormone levels.