Inactivation of Thyrotropin-releasing Hormone (TRH) by the Hormonally Regulated TRH-degrading Ectoenzyme A Potential Regulator of TRH Signals?

The peptidergic signal substance TRH is inactivated by the TRH-degrading enzyme, a peptidase that exhibits a high degree of substrate specificity and other unusual characteristics. The tissue-specific regulation of the adenohypophyseal enzyme by estradiol and thyroid hormones suggests that it may serve an integrative function in modulating the response of adenohypophyseal target cells to TRH and thus pituitary hormone secretion. The high enzymatic activity of neuronal cells indicates that centrally this peptidase also might act as a terminator of neural TRH signals.