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Module 10: Figure thyrotroph regulation

Regulation of TSH secretion by thyrotrophs.

Release of thyroid-stimulating hormone (TSH) by thyrotropin-releasing hormone (TRH) depends on the activation of phospholipase C (PLC) to produce inositol 1,4,5-trisphosphate (InsP3). The latter then releases Ca2+ from the endoplasmic reticulum to induce the exocytosis of the vesicles containing TSH. Ca2+ may also act to switch on the expression of the β-TSH gene. The latter is also under negative control by T3, which is produced locally from T4 by an enzyme located on the folliculostellate (FS) cells.