GLOSSARY

Thyroid Hormone Receptor Signaling
Thyroid hormone receptors regulate gene expression in response to thyroid hormone, particularly T3. TR-alpha and TR-beta isoforms show different tissue distributions and support distinct aspects of development and metabolic regulation.

Access to the receptor

Transporters deliver hormone into cells, while deiodinase enzymes influence local T3 availability. Serum T4 or T3 therefore describes exposure only partly, because intracellular handling changes the ligand concentration near the receptor.

Transcriptional control

Many thyroid hormone receptors interact with DNA and RXR partners. Ligand binding changes the recruitment of coregulators. The effect can activate or repress different genes depending on the regulatory context.

Applied interpretation

Normal thyroid action requires an intact chain from transport and conversion to receptor activity. In exercise physiology, altered energy expenditure cannot be attributed to a thyroid receptor change merely because a blood hormone concentration has shifted.