Thyrotropin-releasing hormone membrane receptors

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The central focus of thyroid system control is the pituitary thyrotroph cell. Figure 1 summarizes the major events in thyrotroph cell control of thyrotropin (TSH) synthesis and release. Hypothalamic thyrotropin releasing hormone (TRH) binds to its receptor, stimulating the synthesis and release of TSH. Based on available evidence it appears that TRH-receptor Interaction increases intracellular free calcium concentrations both by mobilization from intracellular pools and by increasing transport via cell membrane calcium channels (2). The increased cytoplasmic calcium activates TSH release. Cyclic AMP may play a role both TRH and cAMP seem capable of increasing calcium inflow into the thyrotroph, as well as mobilizing calcium from intracellular pools. However, cAMP does not appear to be the primary mediator of the TRH effect. 

TSH Thyroid-stimulating hormone or thyrotropin a glycoprotein hormone released from the anterior pituitary in response to increased levels of TRH. TSH binds to TSH receptors on the basal membrane of epithelial cells of the thyroid gland to stimulate the release of the thyroid hormones, Tj and T. ... 

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