Prolactin-releasing hormone

Prolactin releasing hormone, also known as PRLH, is a hypothetical human hormone or hormone releasing factor. Existence of this factor has been hypothesized as prolactin is the only currently known hormone for which almost exclusively negative regulating factors are known (such as dopamine, LIF, some prostaglandins) but few stimulating factors. While many PRL stimulating and enhancing factors are well known (such as TRH, oxytocin, steroid hormones) those have primary functions other than stimulating prolactin release and the search for hypothetical releasing factor or factors continues.

The prolacting releasing peptide identified in 1998 was a candidate for this function, however as of 2008 it appears its function is not yet completely elucidated.