Medical Health Encyclopedia

Growth Factors and Angiogenesis. Macrophages also produce growth factors, which are of particular interest because they play important roles in angiogenesis, a natural process by which new blood vessels form.

Vascular endothelial growth factor (VEGF) is secreted by endometrial cells, and so is of special interest. Under normal conditions, VEGF is secreted within the uterus. When oxygen levels drop following menstruation and blood loss, VEGF levels rise and promote the growth of new blood vessels. This process is important for repairing the uterus following menstruation.

When endometrial cells land outside the uterus, however, investigators theorize that this same process occurs with unfortunate results. The cells secrete VEGF when they are deprived of blood and oxygen, which in turn stimulates blood vessel growth. In this case, however, blood vessel growth serves to promote implantation outside the womb.

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Other growth factors involved in angiogenesis that may play a role in endometriosis include transforming growth factors (such as TGF-beta), platelet-derived endothelial growth factor (PD-ECGF), and tumor necrosis growth factors.

Inflammatory Response. The damage, infertility, and pain produced by endometriosis may be due to an over-active response by the immune system to the early presence of endometrial implants. The body, perceiving the implants as hostile launches an attack. Of particular note, levels of large white blood cells called macrophages are elevated in endometriosis. Macrophages produce very potent factors, which include cytokines (particularly those known as interleukins) and prostaglandins. Such factors are known to produce inflammation and damage in tissues and cells.

Genetic Factors

A major study is underway to uncover the genetic factors that predispose certain women to endometriosis. The incidence of endometriosis in women who have a mother or sister with the disorder may be up to 10 times higher than average.