Relaxin

Relaxin is a naturally occurring peptide hormone, structurally related to insulin, with a molecular weight of about 6000 Da. It is primarily produced by the corpus luteum in females and also found in males. In pregnancy, relaxin plays a key role in reproductive physiology by relaxing the uterine muscle and loosening pelvic ligaments to facilitate childbirth. Beyond reproduction, relaxin acts as a potent vasodilator through activation of nitric oxide pathways and other signaling cascades (such as PI3K/Akt and VEGF), leading to increased cardiac output and renal perfusion. These properties have led to its investigation as a treatment for acute heart failure, where it has shown favorable trends in early clinical trials[3][7][8]. Relaxin exerts its effects mainly via G protein-coupled receptors known as relaxin family peptide receptors (RXFP1-4), with RXFP1 being the primary receptor mediating cardiovascular actions[6][8]. Recombinant forms such as serelaxin have been developed for therapeutic use[4].