I see a lot of endometrial cancer patients- which means I see a lot of overweight patients. Why you ask? What does body size have to do with cancer?
The female body is a very fine tuned machine. Each month during the menstrual life, the pituitary gland sends out signals that tell the ovary to start producing an egg and making estrogen. This estrogen causes the lining of the uterus to thicken in anticipation of a fertilized egg making a landing. After the egg is released (around day 14 if your counting) the ovary converts over to making progesterone. This "matures" the lining of the uterus, turning the "proliferative endometrium" into a "secretory endometrium". The corpus luteum (the old cells in the ovary that helped kick start the egg and that have now switched over to progesterone production) only has a life of 14 days. Once this corpus luteum "dies" the progesterone levels drop, and this withdrawal of progesterone causes the lining of the uterus to shed... yep Aunt Flo. And the cycle starts over.
So what happens if you don't ovulate (produce an egg)? No progesterone conversion, no maturation of the lining of the uterus, and the continued estrogen stimulation continues to cause growth of the lining of the uterus. Now, this may become unstable, and an unstable endometrium likes to slough off. This usually happens when you least expect it- like when you wore those white pants to the office. This is what most women refer to as irregular periods. Sometimes this sloughing is on a semi-regular basis, and can fool some women into thinking that they are ovulating. Sometimes its heavy, sometimes nothing for months at a time.
So what does this have to do with the size of your waist? Fatty tissue in our bodies has an enzyme called aromatase. This converts male hormones such as androstenedione, produced by the adrenal glands, into estrone. Estrone acts as a weak estrogen, stimulating the lining of the uterus to continually grow. However, this estrone also fools the brain. Instead of sending out signals such as FSH that would stimulate the ovary to produce another egg, the estrone causes a release of LH which tells the ovary to produce more androstenedione. This androstenedione is then converted into more estrone thus starting the cycle over again. Although estrone is a weak estrogen, a long enough period of stimulation will eventually thicken the lining of the uterus significantly. Over time, this continued stimulation of growth, without the maturing effects of progesterone lead to occasional genetic abnormalities. These genetic abnormalities accumulate in the form of pre-cancers and eventually cancer. One example of one of these pre-cancers is a condition called endometrial hyperplasia. I will discuss this condition, especially complex atypical endometrial hyperplasia, in another blog post as it gets quite complex. So, the more fat you have, the less likely you are to ovulate regularly. And the less likely that you ovulate the less likely you are to produce progesterone. So you see, it's actually the regular progesterone induced maturation and sloughing of the lining of the uterus that prevents endometrial cancer.
It's obviously more complex than that however. Not all obese patients develop uterine cancer, and not all patients with uterine cancer are obese. However this appears to be the major risk factor, and the reason why America's endometrial cancer rates continue to rise. So what can you, as a patient, due to prevent individual cancer? It's simple–exercise, eat right, and lose weight. If you're still in menstruating years, make sure that you are actually ovulating if you're not on some form of progesterone containing birth control. If you don't ovulate, and you suspect that your estrogen levels are too high, talk to your doctor about some form of semi-regular progesterone supplementation. Lastly, if you notice any abnormal bleeding, particularly if you're overweight or menopausal please see your doctor as soon as possible.
Until next time…
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