This is not a new question! People have suffered and wondered about the causes of gallstones for more than a thousand years. Egyptian mummies have been found with gallstones. 10-20% of people will develop gallstones at some point in their lives. Gallstones are either cholesterol gallstones or pigmented gallstones. The pigmented stones are created by crystallization of bilirubin, which is a substance in our bile. Cholesterol stones develop when there is abnormal metabolism of cholesterol for some reason and the cholesterol is not soluble within the bile, which also results in crystal of cholesterol.
In either case, a small nucleus of the crystal develops and then aggregates into a larger ‘stone’. Imagine a grain of sand which is like a tiny snowball and the more it rolls around it gathers more crystals and becomes larger and larger. The older you get, the more chance you have of developing them. But why? Many times this can only be chalked up to ‘bad luck’. But, there are some factors which predispose people to develop gallstones. One is heredity. Those of American Indian or Mexican heritage have increased risk. If your mother, father, or grandparent had gallstones you are at increased risk as well.
Being female increases your risk, but this is primarily due to either being pregnant or taking birth control pills. Why is it women develop gallstones more than men? Both pregnancy and oral contraceptives change the relationship in the levels of estrogen and progesterone. Both of these hormones change the relationship of cholesterol metabolism leading to crystal and then stone formation. Not everyone with high cholesterol develops gallstones and many of those who actually have cholesterol stones do not have high levels of cholesterol found in the blood. Again, it is more of a function of whether or not the cholesterol within the bile is soluble, or forms crystals.
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