Is the lack of research into the interplay between relaxin and the musculoskeletal system a result of relaxin having historically just been seen as a lady-pregnancy thing?
University of Iowa gynecologist Dr Michael Haugsdal
noted a lack of established information on the musculoskeletal impact of hormones, particularly beyond the context of pregnancy-induced changes.
[…] During his education, Haugsdal said that relaxin was most often mentioned in the context of pregnancy, while [Dr Robert Westermann
, head of the Young Adult Hip Preservation Clinic at the University of Iowa] confirmed that it was not a part of orthopedic education.
These facts are, I am sure, entirely unrelated.
Anyway, thankfully, some research is now being done, thanks to a female medical student called Emily Parker who noticed the 20 year gap between early relaxin-musculoskeletal studies and literally anything else happening, and decided to take on this particular gendered data gap.
And in her recent write-up of her research
, she notes that the representation of relaxin as a “pregnancy” hormone is a category error:
In reality relaxin is a menstrual cycle hormone, peaking just prior to menses, with collagen degradation being a key function. It binds receptors upregulated by the preceding estrogen peak, and activates collagenases also increased in number by the peak of estrogen. Thus, during the menstrual cycle luteal phase, relaxin binds receptors in target tissue, triggering degradation of existing collagen while suppressing synthesis of new collagen.
This mechanism of action is problematic for women because they express receptors beyond the confines of the reproductive system. Prior ACL/relaxin studies confirmed that female ACLs strongly bind relaxin, while male ACLs do not. Later clinical studies showed a significant, positive correlation between high relaxin levels and high ACL injury rates. Importantly, recent studies even bring up potential interventions such as menstrual cycle tracking and hormonal contraceptives.