Corticotropin-releasing factor is produced by rat Leydig cells and has a major local antireproductive role in the testis.

Cultured rat Leydig cells secreted considerable amounts of corticotropin-releasing factor (CRF). A major stimulus for Leydig cell-derived CRF was the trophic hormone LH/hCG, which released the peptide in a dose dependent fashion. Incubation of Leydig cells with a CRF antagonist revealed tonic suppression of basal and hCG-stimulated testosterone production by endogenously produced CRF. These findings demonstrate that CRF acts via functional Leydig cell receptors to exert autocrine inhibitory actions on Leydig cell steroidogenesis. In the testis CRF acts as an antireproductive hormone and as a major local inhibitory regulator of Leydig cell function.