Endometriosis is when the endometrium, tissue that lines the inside of the uterus, is found outside of the uterus in other ares of the body, except the spleen. The growths respond to normal hormonal surges, to grow or shed, but the blood generated has nowhere to go, so causes pain, inflamtion, and adhesions.

Endometriosis tissue also generates small amounts of hormones themselves thereby meaning they continue to grow very slowly fuelling themselves – even after treatment for hormones etc..