Thyroid hormone acts in virtually every biological sys- tem in vertebrates by controlling the expression of dif- ferent sets of genes. To achieve this, thyroid hormone inter- acts with two receptors (TR), TR and TR , located in the nucleus of its target cells, which turn gene transcription on or off and thus mediate the biological effects associated with the thyroid secretion (1, 2). The distribution of TR and TR among different target tissues is not homogeneous: TR pathways are implicated in the brain, skeletal muscle, heart, and bone, whereas the TR pathways play a metabolic role in liver and adipose tissue (3). Together both TR isoforms control a vast network of biological processes that includes critical roles in development, growth, and metabolic homeostasis (4).
Crossing the Hurdles of Thyroid Hormone Receptor – Activation.
Miriam O. Ribeiro and Antonio C. Bianco Endocrinology, March 2011; doi: 10.1210/en.2010-1491