Corticotrophin releasing hormone: its potential for a role in human myometrium

Aside from its role as a hypothalamic stress hormone, corticotrophin releas ing hormone (CRH) is also a placental hormone, at least in primates. Althou gh the function of placentally derived CRH remains to be fully elucidated, elevated CRH levels have been associated with premature labour, suggesting that the hormone may be involved in regulating the duration of pregnancy, I ndeed, pregnant human myometrium expresses functional CRH receptors (CRH R1 and CRH Rt subtypes) thought to signal predominantly via the second messen ger cAMP. Thus, like other cAMP-producing hormones in the myometrium such a s beta (2) agonists, CRH may play a part in maintaining uterine quiescence. However, several of the CRH receptor isoforms identified to date have a re duced ability to activate adenylate cyclase, raising the question as to whe ther they are linked to other signal transduction pathways. Here, we discus s critically the evidence for the peptide's role in regulating contractilit y, both directly at the myometrium and indirectly via the fetal membranes a nd decidua, The possibility of a role in myometrial growth modulation is al so described.