thyroid hormone mediated signaling pathway

Definition

Target type: biologicalprocess

The series of molecular signals mediated by the detection of a thyroid hormone. [GOC:hjd]

Thyroid hormone (TH) mediated signaling is a crucial endocrine pathway that regulates a wide range of physiological processes, including metabolism, growth, development, and homeostasis. The pathway begins with the synthesis and secretion of TH from the thyroid gland. TH consists of two primary hormones, thyroxine (T4) and triiodothyronine (T3), which are derived from the amino acid tyrosine. T4 is the primary hormone produced by the thyroid gland, but T3 is the more active form of the hormone. T3 is generated from T4 through deiodination by enzymes known as deiodinases. Once secreted into the bloodstream, TH circulates bound to carrier proteins, primarily thyroid-binding globulin (TBG).

Upon reaching target tissues, TH dissociates from its carrier proteins and enters cells. Inside cells, TH binds to nuclear receptors, specifically thyroid hormone receptors (TRs). TRs are members of the nuclear receptor superfamily, which are transcription factors that regulate gene expression. TRs exist as heterodimers with retinoid X receptors (RXRs). In the absence of TH, TRs are bound to DNA in the promoter regions of target genes, repressing their transcription. When TH binds to TRs, the complex undergoes a conformational change, leading to the recruitment of co-activators and the initiation of transcription.

The binding of TH to TRs and subsequent activation of gene expression triggers a wide array of cellular responses. These responses include:

- **Metabolic regulation**: TH plays a critical role in regulating metabolism, particularly energy expenditure, carbohydrate metabolism, and lipid metabolism. It stimulates the production of heat (thermogenesis) and increases basal metabolic rate, contributing to the regulation of body temperature.
- **Growth and development**: TH is essential for normal growth and development, especially during fetal and neonatal stages. It regulates bone growth, brain development, and maturation of the nervous system.
- **Cardiovascular function**: TH influences heart rate, contractility, and blood pressure. It also plays a role in regulating blood lipid levels.
- **Homeostasis**: TH helps maintain homeostasis by regulating body temperature, water balance, and electrolyte balance.

The intricate interplay between TH and its receptors highlights the complexity and importance of this signaling pathway. Dysregulation of TH levels or signaling can lead to a variety of disorders, including hypothyroidism and hyperthyroidism. Understanding the mechanisms of TH signaling is crucial for developing effective treatments for these conditions and other related diseases.'
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Proteins (3)

Compounds (19)