Iron deficiency anemia
Red blood cells are responsible for transporting oxygen throughout the body; iron is necessary for the production of those blood cells. Without enough iron, the body cannot produce sufficient red blood cells to adequately distribute oxygen, a condition called iron deficiency anemia. Malabsorption of nutrients, like iron, is common for individuals with celiac disease, and there is a high occurrence of anemia (up to 33%) in celiac disease patients. The relationship is so strong, in fact, that people whose anemia has no obvious cause (i.e. blood loss) should be tested for celiac disease.
Early onset osteoporosis or osteopenia
Osteopenia is the thinning of bones that occurs when the body uses up bone mass faster than it can get replaced. At its most severe, this condition becomes osteoporosis, in which bones become so brittle and fragile that even a cough might cause bone breakage. Damage to the small intestine, such as is present for untreated or newly diagnosed celiac patients, can prohibit calcium absorption, leading to osteopenia and osteoporosis at a much younger age than for unaffected individuals. Adherence to a gluten-free diet can actually result in improved bone density, though it is also important to take other, more traditional precautions to maximize bone health.
Infertility and miscarriage
Infertility is defined as the inability of a couple to achieve pregnancy after 12 months of regular intercourse without contraceptive use. A number of studies over the last couple of decades have suggested some link between infertility (and/or miscarriage, an inability to successfully carry a fetus until it can survive outside the womb) and celiac disease, though the relationship is not yet completely clear. There is a slightly higher prevalence of undiagnosed celiac disease in women experiencing infertility, and adoption of a gluten-free diet has seemed to lead to increased fertility in those patients.
Lactose intolerance is the inability to properly digest the sugar (lactose) found in milk and other dairy products. As this type of digestion occurs in the small intestine, it is not surprising that lactose intolerance and celiac disease commonly co-occur, in a condition called secondary lactose intolerance. As many as 24% of people with lactose intolerance may also have celiac disease. Interestingly, by following a gluten-free diet and allowing the intestinal villi to heal, lactase enzyme production may be re-established, effectively ending the lactose intolerance.
Vitamin and mineral deficiencies
A vast amount of our vitamin and mineral absorption occurs through the small intestine. When the intestinal villi are damaged like they are with celiac disease, the body is unable to absorb the vitamins and minerals from food as it passes through the system. This can lead to deficiencies of iron (anemia), calcium (osteopenia), fiber, zinc, magnesium, folate, niacin, riboflavin, vitamin B-12, vitamin D and, less commonly, copper and vitamin B-6. Many of these deficiencies can be treated with supplements, once a gluten-free diet is in place and the villi begin to heal.
Central and peripheral nervous system disorders
There is no doubt that there is a relationship between celiac disease and an assortment of nervous system disorders, ranging from neuropathy and ataxia to depression and anxiety. This is currently an area of significant study in the celiac disease community, and the relationship is thought to be comprised of three possible factors: 1) nutritional deficiencies resulting from vitamin/mineral malabsorption; 2) possible “clustering” of autoimmune conditions; and 3) structural similarities between proteins targeted by celiac disease and those present in the brain.
Exocrine pancreatic insufficiency (EPI) is a condition in which the pancreas fails to produce enzymes necessary to break down and digest food properly. While the two conditions do not seem to have a cause/effect relationship, there is indication that they co-exist in about 5% of celiac cases. For those patients with a formal diagnosis of celiac disease for whom adherence to a gluten-free diet does not seem to be enough to treat symptoms, testing for EPI is recommended, as it may be responsible for the non-responsiveness.
Gall bladder malfunction
The gall bladder is a tiny organ below the liver that produces bile to assist in the breakdown and digestion of fats. This is a function critical to digestion, and a malfunctioning gallbladder can lead to a vast array of symptoms from heartburn and indigestion to crippling abdominal pain. Damage to the small intestine can cause communication difficulties to the organs, like the gallbladder, that secrete digestive enzymes, leading to a domino effect; an estimated 60% of celiac patients have liver, gallbladder or pancreatic issues. Some sources even suggest that celiac disease is the cause of gallbladder disease; it is important that people suffering with gallbladder problems seek testing for celiac as well.Source: https://celiac.org/celiac-disease/understanding-celiac-disease-2/what-is-celiac-disease/24477-2/