It is known to mediate the hemodynamic changes that occur during pregnancy, such as increased cardiac output, increased renal blood flow, and increased arterial compliance. It also relaxes other pelvic ligaments. It is believed to soften the pubic symphysis. In males, relaxin enhances motility of sperm in semen.
Relaxin is a protein hormone of about 6000 Da and belongs in the insulin superfamily. It consists of 7 peptides of high structural but low sequence similarity.
In the female, it is produced by the corpus luteum of the ovary, the breast and, during pregnancy, also by the placenta, chorion, and decidua. In the male, it is produced in the prostate and is present in human semen.