How do thyroid hormones regulate cellular metabolism?

Thyroid hormones, primarily triiodothyronine (T3), regulate cellular metabolism by acting at the genetic level to alter protein synthesis. Once T3 enters a target cell, it binds to nuclear receptors, and the resulting complex interacts with DNA to increase the transcription of specific genes into mRNA. This process stimulates the production of various enzymes and proteins that govern metabolic activity.12

Key metabolic effects include:

• Energy Utilization: T3 increases the synthesis of proteins that regulate how cells consume oxygen and utilize nutrients within mitochondria. It specifically activates pathways that dissipate energy as heat.1
• Nutrient Metabolism: These hormones stimulate carbohydrate utilization and lipid metabolism, which includes increasing the utilization of cholesterol.1
• Systemic Activation: By influencing protein expression, thyroid hormones promote central and autonomic nervous system activity, leading to increased heart rate and cardiac muscle contraction.1

While thyroxine (T4) is the primary hormone secreted by the thyroid gland, it functions largely as a precursor that is converted into the more biologically active T3 by deiodinase enzymes within target tissues.2