Hypothalamic tripeptide (thyrotropin-releasing hormone)
A hypothalamic tripeptide that triggers pituitary TSH release; used as a pharmacological probe for pituitary function and investigated for cognitive enhancement.
Abstract
TRH (thyrotropin-releasing hormone; pyroglutamyl-histidyl-prolinamide; CAS 24305-27-9; molecular formula C16H22N6O4; molecular weight 362.39) is a hypothalamic tripeptide that activates pituitary TRH receptors to trigger TSH release. Discovered independently by Schally and Guillemin in the late 1960s (Nobel Prize 1977). The compound is the smallest peptide hormone of the hypothalamic-pituitary axis. Pharmacologically, exogenous TRH has been used as a clinical probe of pituitary thyrotroph function (the TRH stimulation test, now largely supplanted by sensitive TSH assays). Beyond TSH release, TRH receptors are distributed throughout the CNS and TRH has direct effects on arousal, mood, and cognitive function; clinical trials in depression, ALS, and spinocerebellar ataxia have been mixed. Plasma half-life is approximately 5 minutes, severely limiting clinical use; analog development has produced taltirelin (approved in Japan for spinocerebellar degeneration) and other TRH receptor agonists with extended pharmacokinetics. Used as the canonical hypothalamic peptide for pituitary axis research.
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