What causes adenomyosis?

Adenomyosis happens when endometrial-like tissue grows into the muscular wall of the uterus (the myometrium). Each cycle, this tissue can still respond to hormones—swelling and bleeding in place—which can drive inflammation, uterine tenderness/enlargement, heavy bleeding, and cramping that may be severe.

What causes it in the first place isn’t fully understood. What we do know is that adenomyosis appears to be multifactorial, with overlapping genetic, hormonal, and immune/inflammatory influences likely contributing; newer research is also exploring cellular and metabolic changes inside the uterine environment that may help explain why symptoms persist.

A key point is that adenomyosis stays within the uterus (it doesn’t “spread” throughout the pelvis the way endometriosis can), though it can be diffuse or form more localized areas called adenomyomas. Because causes and patterns vary, our team focuses on clarifying your individual picture—your symptoms, imaging findings, and any overlap with endometriosis—so you can move toward a treatment plan that matches your goals.