Editorial [Hot Topic: Relaxin and Related Peptides (Guest Editors: A. Ferlin and C. Foresta)]

Relaxin has long been regarded as a hormone of pregnancy and has been of interest only in females. However, recent discoveries in rodents have provided evidence that relaxin is a multi functional hormone and may have reproductive and non-reproductive actions in both females and males. Relaxin is a potent anti-fibrotic agent capable of remodelling collagen in various tissues including the cervix, vagina, kidney, heart, lung and liver. Relaxin has also been reported to counteract allergic reactions and protect the heart against ischaemic injury. The identification of the possible roles of relaxin in the pathophysiology of many diseases and the possible therapeutic applications of relaxin are experimental areas of great current interest to relaxinologists. Also adding great interest to this area are recent discoveries of novel hormones that are structurally similar to relaxin such as brain-specific relaxin- 3 and testis-specific INSL3. Whereas the functional significance of relaxin-3 remains to be elucidated, INSL3 has been clearly demonstrated to play a fundamental role in testicular descent in the male, and there is limited evidence that it may also contribute to oocyte development in the female. However, other promising endocrine actions of this hormone in adults have been hypothesised. Relaxin and INSL3 have been also implicated in cancer. Finally, the recent identification of the receptors for relaxin, relaxin-3 and INSL3 makes possible more rigorous approaches toward an understanding of the cellular and molecular mechanisms whereby these three hormones bring about their actions.