Biology of the relaxin-like factor (RLF)

The relaxin-like factor (RLF) is a novel member of the insulin-IGF-relaxin family of hormones and growth factors. Also known as the Leydig cell insulin-like factor (Ley-I-L), this peptide and the mRNA encoding it appear to be expressed in very large quantities in the Leydig cells of the testis. However, it is also produced in the ovary of a number of species in both follicular theca cells and in the corpus luteum of the cycle and pregnancy. RLF gene transcripts have been identified at a much lower level of expression throughout the bovine female reproductive tract and also in the hypothalamus. Although data are limited, it would appear that RLF represents a new differentiation-related factor with specific functions linked to reproductive physiology in male and female mammals.