Endometriosis is a disease characterized by the growth of tissue resembling the endometrium, or tissue that lines the uterus, outside the uterus, usually around other organs in the pelvic cavity. These extra-uterine growths swell and shed with the monthly hormonal cycle, just like the normal endometrium. However, the lesions cannot be excreted normally with menstruation, and therefore lead to pain, swelling, and infertility. Endometriosis is also associated with an increased risk of cancer.

What is metaplasia?

There are several potential risk factors associated with endometriosis, but the exact cause of the disease is not well-understood. It is likely a combination of several factors.

Metaplasia is the term used to describe the abnormal conversion of one cell type into another. In the case of endometriosis, it is a proposed explanation for development of the disease: normal abdominal cells change and become endometrial-like cells in places they should not.

Why does metaplasia occur?

Some researchers think this conversion of cells into a different cell type occurs at the embryonic stages of development. Others think some cells maintain the ability to undergo transformations as adult cells, possibly in response to environmental triggers or irritation, such as retrograde menstruation or hormonal changes such as the ones that occur at the onset of puberty. It is also possible that both scenarios occur and contribute to the development of endometriosis.

It is also possible that the environmental trigger that causes metaplasia also increases inflammation and immune dysfunction — there is some evidence suggesting that endometriosis may be, at least in part, a disease associated with immune dysfunction.

Finally, there may be genetic factors promoting the occurrence of metaplasia and this may be one of the reasons endometriosis is more likely to occur in families.


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