08/19/2026
We used to think of skeletal muscle primarily as a mechanical tissue that contracts, moves the skeleton, and burns energy. We now know that muscle is also an endocrine organ. When muscle contracts, it releases myokines, signaling molecules that communicate with tissues throughout the body.
One of the hormones produced by muscle is irisin. Irisin is being investigated for its role in glucose metabolism, insulin sensitivity, inflammation, mitochondrial function, brain health and the muscle–brain axis.
For women, this conversation becomes particularly important as they move through hormonal transitions such as menopause. Declining estrogen can alter body composition and metabolic health, making preservation of muscle mass and function increasingly important.
But here’s the nuance: Irisin isn’t the reason exercise works. Exercise creates a complex orchestra of signals, including myokines, metabolites, neural signals and hormonal responses. Irisin is one instrument in that orchestra.
We’re still learning exactly how important each instrument is. The bigger message is much simpler: Muscle is metabolic tissue. Muscle is endocrine tissue. Muscle is communication tissue. So don’t train only for appearance. Train for the messages your muscles send to the rest of your body.