Oxytocin is a relatively small peptide hormone (nine amino acids) that is produced in the posterior pituitary gland. Although it is produced in both men and women, the most well known function of oxytocin is in females where it acts as a facilitator of uterine contractions during labor, and as a stimulator of milk release from the breasts in the post-partum period. More recent research has implicated oxytocin in the emotional bonding response that occurs between females and their infant offspring, and also that which occurs with adult romantic partners over time. You may have heard that oxytocin is released after sex especially in women (which may be why women tend to be more affectionate afterwards). Oxytocin is also FDA approved as a drug to facilitate labor in women and to help with post childbirth bleeding.
Like many hormones in the body, science is discovering that oxytocin may have a wide variety of actions on multiple tissues – activities beyond the classical ones for which it is most well known. Most recently evidence has popped up suggesting that oxytocin is a factor in the regeneration of muscle tissue and that its levels are suppressed with age.
Researchers at UC Berkeley published a paper demonstrating that oxytocin is an indispensable factor in the healthy repair and maintenance of skeletal muscle tissue. They used young and old mice and showed that levels of oxytocin in the older mice were much lower than the younger mice. Administration of oxytocin (by subcutaneous injection) for a few days restored the ability of muscle to repair itself in these older mice to levels seen in younger mice. Conversely, mice bred with inability to produce oxytocin were born normal but quickly developed sarcopenia (muscle loss associated with aging).
The mechanism of this enhanced muscle regenerative capacity is thought to be due to increasing the proliferation and activation of muscle satellite cells. Muscle satellite cells are known to decrease with aging and they serve a key role in muscle recovery and growth. Injury (exercise induced or via trauma) causes the release of certain chemical signals which stimulate satellite cells to fuse with their parent muscle cells where they add myonuclei (the powerhouse of protein synthesis within the muscle cell).
It has been shown previously that muscle cells possess functional oxytocin receptors and that muscles themselves can manufacture oxytocin. One study in particular showed that in cattle the expression of oxytocin in muscle is increased dramatically in cattle receiving the anabolic steroid implant Revalor H, and it is speculated that oxytocin may be related to the increased muscle mass that results. The UC Berkeley study now shows that direct systemic administration of oxytocin may have positive effects upon skeletal muscle as well.
As I mentioned previously, oxytocin is an FDA approved drug so its safety profile has been examined. However its intended use is short term, and any usage to treat a condition such as sarcopenia would require more long term administration. Oxytocin is also available freely from veterinary stores and is actually not very expensive. I don’t really know what dosages might theoretically work in a human (if any dose would work at all).