OTHER TYPES OF DIABETES | Added: 12, August 2017



GESTATIONAL AND PREGESTATIONAL DIABETES

What are some connections between diabetes and pregnancy?

One connection between diabetes and pregnancy is pregestational diabetes. This is when a woman already has insulin-dependent diabetes and becomes pregnant (see below). The most well-known connection between diabetes and pregnancy is a condition called gestational diabetes. In the United States, it occurs in about 4 to 9 percent of pregnant women (the percentage varies depending on the study). Worldwide, it has been reported by some studies to occur in about 19 percent of pregnant women.

What is gestational diabetes?

Gestational diabetes occurs when a pregnant woman develops high blood glucose levels, even if she did not have diabetes before pregnancy. This type of diabetes generally develops during the woman’s second trimester and usually disappears after the baby is born. According to the American Diabetes Association, this condition is also thought to raise the mother’s and child’s risk for developing type 2 diabetes later in life.

Why do some pregnant women develop gestational diabetes?

Although not all studies agree, most research seems to indicate gestational diabetes may be caused by the hormones in the fetus’s placenta. This connection between the mother and fetus, which supplies the nutrients the baby needs, may block the action of the mother’s insulin throughout the body. If left untreated, gestational diabetes can result in very large babies and possibly the need for a caesarean delivery.

What is the O’Sullivan test?

The O’Sullivan test is a one-hour glucose-tolerance test (GTT) that is given to pregnant women to screen for gestational diabetes. It is most often performed between the 24th and 28th weeks of pregnancy.

What is pregestational diabetes?

Pregestational diabetes is used to describe the condition of a woman who already has insulin-dependent diabetes and becomes pregnant. Like gestational diabetes, pregestational diabetes can have consequences for the woman’s infant, especially if the mother’s blood glucose levels are not controlled during pregnancy.

What percentage of pregnant women develop pregestational or gestational diabetes?

Although studies vary, it is estimated that gestational diabetes affects around 4 to 9 percent of pregnant women, or 4 to 9 of every 100 women who become pregnant in the United States. It is also estimated that gestational diabetes is 100 times more common than pregestational diabetes. There are also ethnic and racial groups that are at higher risk for gestational diabetes. It is thought that the Pima Indians of Arizona have 40 percent chance of having gestational diabetes, or a tenfold higher risk than the general population. Other groups are also at an increased risk, including African Americans, obese women, women who are at an older maternal age at pregnancy, women with a family history of diabetes, women whose babies are large for their gestational age, and women with a prior history of gestational diabetes during other pregnancies.

Do any groups have a lower risk of developing gestational diabetes?

Yes, it has been estimated that teenage pregnant women have a lower risk-about one-fourth lower-of developing gestational diabetes than pregnant women age 35 or older. In addition, certain studies have indicated that Asian, Asian American, and Filipino women seem to have a lower risk of developing gestational diabetes, but more studies are needed to confirm the results.

About 5 to 10 percent of women in the United States will be affected by gestational diabetes.

How can having pregestational diabetes affect a woman’s unborn child?

If a mother who has insulin-dependent diabetes has uncontrolled blood glucose, excess glucose is often transferred to the fetus. Because of this, the baby’s system secretes an increased amount of insulin, which can cause an increase in tissue and fat deposits in the baby. According to Stanford Children’s Health, these deposits can increase the risk of birth defects, especially during the development of the fetus’s heart, brain, spinal cord, and gastrointestinal system. In many cases, too, the infant of a mother with pregestational diabetes is often larger than expected for the gestational age.

Can a woman develop diabetes by becoming pregnant?

No, there is no research that supports the idea that pregnancy causes a woman to develop diabetes, but there is the possibility of developing gestational diabetes. However, some research indicates that if a woman has had gestational diabetes, she may be at a higher risk for developing type 2 diabetes later in life. Other research seems to indicate that breastfeeding a child will lower the mother’s risk of developing type 2 diabetes. But overall, no true connection between becoming pregnant and developing diabetes has been shown.

In what way does gestational diabetes differ from pregestational diabetes in terms of the fetus?

According to Stanford Children’s Health, pregestational diabetes (if the mother has uncontrolled blood glucose levels) has been associated with birth defects in certain organs of the fetus as they form. Gestational diabetes generally does not cause birth defects. This may be because women who develop gestational diabetes develop it later in their pregnancy. Thus, most women will have normal blood glucose levels during the first trimester when the fetus’s organs are forming.

What is the White Classification?

The White Classification of Diabetic Pregnancies classifies the risks associated with a woman who is pregnant and has diabetes. It was presented by American physician and researcher Priscilla White (1900–1989), who, in 1924, joined the practice of Elliot Joslin and began caring for pregnant women who had diabetes. (She was also one of the founders of the Joslin Diabetes Center in Boston; for more information about Joslin, see the chapter “Introduction to Diabetes,” and for more about the center, see the chapter “Resources, Websites, and Apps.”) White’s system was based on a pregnant woman’s age at the onset of diabetes, the duration of the disease, and whether the woman had any vascular complications. The class system White presented in 1949 included Class A, meaning the diagnosis of the diabetes is based on a glucose-tolerance test and deviates slightly from the normal levels. Class B means the pregnant woman has had diabetes less than ten years, with the onset at age 20 or older, and no vascular disease. The diabetes and associated diseases increases as the classes continued down the alphabet. For example, class F means the pregnant woman with diabetes has nephritis, or inflammation of the kidneys.

How has the White classification changed-and how does it often cause confusion?

As research uncovered information about diabetes, the White Classification of Diabetic Pregnancies listing changed accordingly. Other more complex revisions were made in the classification, based on differences in research and new discoveries of how diabetes affects other parts of the body. For example, one later classification listed class A as involving a pregnant woman having diabetes that can be controlled by diet alone, at any duration or onset age. Class B means the onset age is older than 20, with the duration less than ten years (same as with the White classification). But such listings also become more complicated. For instance, also in this listing, the classes are even farther down the alphabet, such as class H, in which arteriosclerotic heart disease is clinically evident, and class T, which is listed as “prior renal transplantation,” or excessive kidney disease that led to a kidney transplant. Still other classifications list not only other symptoms in each class but add different and/or more classes. Thus, many researchers are now calling for a more standardized classification to simplify-yet explain the complexities of-the list of types of diabetes in pregnant women.

Is there a classification based on just gestational diabetes?

As with many diseases, there are often several classifications. Gestational diabetes also has its own classification that differs from the White and subsequent listings (see above). One of the simplest states that if a pregnant woman can control her diabetes through diet, then it is called class A1; if a pregnant woman needs insulin or oral medication to control her diabetes, then it is called class A2.

Are multiple pregnancies connected to diabetes?

Multiple pregnancies, or pregnancies with more than one fetus, often pose special risks because of the extra demands on the mother’s system. For example, the need for oxygen and other nutrients for each fetus is multiplied. In addition, two common health conditions often affect the mother in multiple pregnancies. One is called preeclampsia, or having high blood pressure and protein in the urine. The other condition is gestational diabetes, or high blood sugar levels during the pregnancy (see above).

Why is breast milk so nutritious for a baby, and how is it connected to diabetes?

After a baby is born, the mother’s breast milk becomes extremely important for the baby’s nutrition. The milk has an amazingly consistent composition, and in most mothers, it is almost a “perfect food” for the child (although it is usually low in vitamin D and fluoride). Certain studies indicate that breastfeeding a baby decreases the risk of respiratory infections, high blood pressure, asthma, and a tendency to develop certain allergies. In some studies, it has been found that when a baby is breastfed, he or she will have a lower incidence of diabetes in later years. But realistically, such benefits also depend on the mother’s lifestyle habits. In other words, the nutrition of the breast milk is directly related to the nutrition of the mother. And if a nursing mother has poor nutrition, then it is often the amount of milk more than the quality that suffers.

Breastfeeding is thought to be much healthier for infants than bottle feeding. One benefit is that breastfed babies have a lower incidence of developing diabetes later in life.

Can breastfeeding protect a mother from type 2 diabetes?

Although several studies seem to indicate that breastfeeding can cause certain changes in a mother’s body that may help protect against type 2 diabetes, the connection has not been proven. But there are some indications that this may be true. For example, one recent study looked at 1,000 ethnically diverse women who had been diagnosed with gestational diabetes. The researchers examined each woman in terms of, for example, lactation intensity and duration. They then tested the women’s blood glucose six to nine weeks after delivery and annually for two years after. By that time, almost 12 percent of the women developed type 2 diabetes, and after accounting for several factors (such as age or other risk factors), the researchers found that women who exclusively breastfed or mostly breastfed were about half as likely to develop type 2 diabetes as those who did not breastfeed. In addition, the researchers found that the length of time a woman breastfed affected her chances of developing type 2 diabetes. Women who breastfed longer than two months lowered the risk of type 2 diabetes by almost half and beyond five months lowered the risk by more than half. But again, more research needs to be done.

Should a mother take diabetes medication while breastfeeding?

If a mother with diabetes decides to breastfeed her baby and takes either insulin or oral medication, it is important to understand certain safety factors while breastfeeding-not only for the baby’s health but for the mother’s sake, too. According to the American Diabetes Association, most diabetes medications can be taken safely as a woman breastfeeds her baby, but the ADA strongly advocates that the woman check with her doctor just to be sure.

What are some tips for mothers who have diabetes and wish to breastfeed their infant?

According to the American Diabetes Association, breastfeeding can be a challenge for mothers who have diabetes, especially because it often makes it harder to stabilize blood glucose levels. The organization suggests that to prevent lower blood glucose levels, the mother should plan to have a snack before or during nursing, drink plenty of fluids (such as water or a caffeine-free beverage) while nursing, and have something nearby to eat in case of low blood glucose so the child’s feeding will not be interrupted. And as always when breastfeeding, it is best to get the right amount of fluids, nutrients, and proteins. Such a nutritional plan can be worked out between a health care professional or dietitian and the breastfeeding mother.

GENES AND VARIOUS TYPES OF DIABETES

What are chromosomes and genes?

A chromosome is the threadlike part of a cell that contains DNA, or deoxyribonucleic acid. It also contains the genetic material of a cell. In some cells, the chromosomes consist entirely of DNA and are not enclosed in a membrane (called a nuclear membrane). In other cells, the chromosomes are found within the central nucleus of the cell and contain both DNA and RNA (ribonucleic acid). Overall, the human genome contains 24 of these distinct, physically separate units. (For more about DNA and RNA, see sidebar.) Arranged linearly along the chromosomes are tens of thousands of genes (from the Greek term genos, meaning “to give birth to”). They are complex protein molecules and are responsible-as a unit or in biochemical combinations-for the transmission of certain inherited characteristics from the parent to the offspring, such as eye color.

The chemical structures of DNA (left) and RNA. These are the molecules so important to maintaining life processes and genes.

What are DNA and RNA?

DNA, or deoxyribonucleic acid, is a nucleic acid found in the body. DNA forms from the repetition of the simple “building blocks of life” called nucleotides. These nucleotides are made of a phosphate, sugar (deoxyribose), and a nitrogen base. There are five types of bases-called adenine (A), thymine (T), guanine (G), cytosine (C), and uracil (U). In a DNA molecule, this basic unit is repeated in a double-helix structure made from two chains of nucleotides linked between the bases. These are linked either between A and T or between G and C. (There are no other links because these particular base structures do not allow any other combinations.) DNA molecules in a single human cell are extremely long. In fact, if one were stretched out and laid end to end, it would measure approximately 6.5 feet (2 meters) in length. The average human body contains 10 billion to 20 billion miles (16 billion to 32 billion kilometers) of DNA distributed among trillions of its cells. In fact, if the total DNA in all the cells from one human were unraveled, it would stretch to the sun and back more than 500 times.

RNA, or ribonucleic acid, is also a nucleic acid found in the body. But unlike DNA, it consists of a single chain instead of a double, and the sugar is ribose rather than deoxyribose. The bases are the same as in DNA, except that the thymine (T) is replaced by another base, uracil (U), which, like the thymine in DNA, links to adenine (A). All RNA exists in three different forms and depending on the cell is formed either in the central nucleus or in the nucleoid region (an irregularly shaped region within certain types of cells).

What is a mutation?

A mutation is a change (or alteration) in the DNA sequence of a gene. Although people often use the term “mutant” in a disparaging manner, mutations are important because of the variation they contribute to a population’s gene pool. Without mutations, there would be no variations and no natural selection within the population-human or otherwise. But mutations can also create harmful effects that cause diseases and disorders. One example of a mutation and resulting disease is sickle-cell disease (also called sickle-cell disorder or anemia). It occurs when a person inherits two abnormal copies of the hemoglobin (the oxygen-carrying protein) gene, one from each parent. The disease causes red blood cells to become rigid and sickle-like in shape and, thus, unable to carry as much oxygen throughout the body.

Have any genes been found in connection with type 1 diabetes?

To date, researchers have identified several different genes that are believed to make a person more likely to develop type 1 diabetes. But they have not found any one single gene that makes all people who inherit it develop the disease (which is why some family members never develop type 1 diabetes, whereas other siblings do develop the disease). Overall, scientists call the genes they have found “diabetes susceptibility” genes.

What is polygenic diabetes?

Polygenic diabetes is actually what doctors most often refer to when discussing type 1 and type 2 diabetes. This means that there are multiple genes-more than one and often several-that can increase the risk of developing type 1 and type 2 diabetes.

What is monogenic diabetes?

Monogenic diabetes is when a person has one gene mutation that causes diabetes. It is estimated that of the human body’s 25,000 genes, more than 20 are associated with monogenic diabetes. An error in one of these single genes can cause an adult or child to develop monogenic diabetes. It accounts for an estimated 1 to 5 percent of all cases of diabetes, depending on the study. According to the American Diabetes Association, it is most common in infants, children, and young adults. Monogenic diabetes includes maturity-onset diabetes in the young (MODY) and neonatal diabetes mellitus (NDM). Not everyone knows that he or she has this single gene and diabetes, with estimates as high as 80 percent of all cases of monogenic diabetes going undiagnosed. In fact, if this form of diabetes is not treated correctly, goes undiagnosed, or is confused with type 1 diabetes, it can lead to problems. (See also MODY and NDM, below.)

Is there genetic testing for monogenic diabetes?

Yes, genetic testing can be used to detect monogenic diabetes, but as of this writing, it is often expensive, and some insurance companies do not pay for the screening. Many health care specialists will test babies who seem to have routine high blood glucose levels. But not all children who have any type of monogenic diabetes will be diagnosed unless they show classic symptoms that lead the health care professional to test for diabetes. This is why it is estimated that almost half of all infants who have or will develop a form of monogenic diabetes go undiagnosed.

Who gets neonatal diabetes mellitus (NDM)?

A rare condition called neonatal diabetes mellitus (NDM) appears in neonates, or babies in the first six months of their life. It is caused by a mutation in a single gene and is considered a form of monogenic diabetes. The number of infants born with neonatal diabetes is not precisely known, but it is thought that one in every 100,000 to 500,000 live births, and about one in 400,000 infants, are diagnosed with neonatal diabetes in the first six months of life.

What is polyglandular autoimmune syndrome, type II?

Polyglandular autoimmune syndrome, type II (it is sometimes used interchangeably with Schmidt syndrome) is a rare autoimmune disorder. It most often occurs when there is an extreme lowering of the levels of several hormones from the glands that secrete the hormones. It usually refers to a combination of many diseases, such as Addison’s disease (an autoimmune adrenal [kidney] insufficiency), autoimmune hypothyroidism or hyperthyroidism, type 1 diabetes mellitus, and/or others.

Is there a difference between neonatal diabetes mellitus and type 1 diabetes?

There is a definite difference between neonatal diabetes mellitus (NDM) and type 1 diabetes (the type most associated with children, although it can occur later in life, too). In particular, type 1 diabetes normally appears after the infant’s first six months of life, whereas NDM can affect the health and development of a child beginning at conception.

Why does neonatal diabetes mellitus occur?

The reason for neonatal diabetes mellitus (NDM) has to do with genes. In fact, to date, more than a dozen different genes (some research suggests more than 20) have been found to cause neonatal diabetes, with some causing both temporary and permanent NDM. For example, according to the American Diabetes Association, if an infant is born with such a defective gene, he or she may have neonatal diabetes throughout adult life. Two of the most common single mutated genes are labeled KCNJ11, which represents 30 percent of all cases of permanent neonatal diabetes, and ABCC8, representing about 20 percent.

How are some children affected by neonatal diabetes mellitus (NDM)?

According to the National Institutes of Health, a child’s health can be affected from birth onward if he or she has neonatal diabetes mellitus. For example, some fetuses with NDM may show signs of slow growth, high blood sugar, dehydration, and even difficulty growing after they are born. Children with NDM may also continue to grow more slowly than other children their age, and if the NDM is severe enough, the child may also experience developmental problems.

Can infants outgrow neonatal diabetes mellitus (NDM)?

Yes, some infants will eventually outgrow neonatal diabetes (in that case it’s called transient neonatal diabetes mellitus), while others will have it all their lives (permanent neonatal diabetes mellitus). Nearly 50 percent of the babies born with neonatal diabetes will see the disease disappear by age 18, but the rest will have permanent neonatal diabetes.

What is autoimmunity?

Autoimmunity occurs when the immune system of a person’s body attacks cells that are considered good for the body, mistaking them for foreign cells. This is one reason that scientists believe type 1 diabetes occurs as the autoimmune system attacks the beta cells (the insulin-producing cells) in the pancreas, and the body can no longer make insulin. (For more about beta cells and the pancreas, see the chapter “How Diabetes Affects the Endocrine System”; for more about autoimmunity and the immune system, see the chapter “Diabetes and Body Connections.”)

What are HLAs?

HLAs, or a set of proteins known as human leukocyte antigens, may predispose a person to diabetes. The HLAs are actually a set of proteins formed by a set of genes. These genes code for certain proteins called antigens that usually identify a person’s cells as their own cells-in other words, they tell the immune cells not to destroy the cells that are part of the person’s body. Researchers suggest that some of the HLAs incorrectly tag a person’s own beta cells as “unfriendly,” causing the immune-system cells to attack the beta cells in a form of autoimmunity that can easily affect blood glucose levels.

What is the MODY form of diabetes?

A genetic form of diabetes, caused by a single gene mutation, is called maturity-onset monogenic diabetes of the young, or MODY. It most often occurs as a child approaches puberty or young adulthood, with most people diagnosed by age 25. It is thought that 3 to 5 percent of all patients with diabetes have MODY (the numbers vary depending on the study). It is also estimated that every child born to a parent with MODY has a 50 percent chance of developing the condition. As for symptoms, the child may or may not show any at all.

Genetically speaking, at least 11 different genes are responsible for the different forms of MODY, and each appears to have different symptoms attached, thus demanding different treatments. For example, according to the Diabetes Genes group in the United Kingdom, people who have a defect in the GCK gene may have hyperglycemia, with an A1c ranging from 5 to 7 percent-with little effect by diet and exercise modification on their blood glucose levels.

Is there a difference between MODY and MODY1?

Yes. In particular, MODY is “maturity-onset diabetes of the young” and due to mutations in the HNF1A gene, while MODY1 is “maturity-onset diabetes of the young, type 1,” caused by mutations in the gene HNF4A on chromosome 20. There are also other MODYs, such as MODY2, due to mutations in the GCK gene on chromosome 7, and depending on the mutation, MODY3, MODY4, and so on. A person with a certain type of MODY will have complications based on the mutation, and in general, these conditions disrupt insulin production. The most common forms are MODY2 and MODY3.

Why are some treatments given to people with MODY1 often questioned?

MODY1 occurs when the beta cells in a person’s pancreas-the cells that secrete insulin-are under stress. Most health care professionals provide the standard therapies given to people with type 2 diabetes in order to make the beta cells secrete more insulin, but a study in 2016 questioned this practice. Most health care professionals treat MODY1 patients with the standard type 2 diabetes drug therapies, including oral medications that make the pancreas’s insulin-secreting beta cells more active. But the researchers believe that the type 2 medications given to a person with MODY1 to increase the activity of the beta cells actually increases stress on those cells. This, in turn, may cause the destruction of the cells, causing even more problems with blood glucose levels. Thus, many researchers caution professionals who diagnose diabetes in patients to determine whether or not the patient has type 2 or MODY1 diabetes before initiating treatments.

What is congenital hyperinsulinism?

Congenital hyperinsulinism is not common, but it occurs when a person has abnormally high levels of insulin. Because of this, the person may experience frequent episodes of hypoglycemia, or low blood glucose levels. It is caused by mutations in the genes that regulate the release of insulin, leading to an oversecretion of the hormone by the pancreas’s beta cells.

OTHER LESSER-KNOWN FORMS OF DIABETES

What diabetic condition is often associated with iron?

“Bronze diabetes” (also called the “Celtic Curse”) is when the body is unable to eliminate excess iron properly, and some of the overabundance of iron collects in the pancreas. As the name implies, a person who has bronze diabetes takes on a bronze skin hue because of the accumulation of iron. This form of diabetes is actually caused by an underlying condition called hemochromatosis, an autoimmune disease that causes the body to store excess iron not only in the liver and pancreas but also in the heart, sexual organs, skin, and joint tissues. If or when the overabundance of iron eventually collects in the pancreas, it can “overload” the organ, creating this type of diabetes.

What is hemochromatosis?

Hemochromatosis is often classified with other “iron-overload” diseases, or those caused by an excessive amount of iron in the body. Normally, a person’s body extracts the correct amount of iron from foods in the intestines. If a person has hemochromatosis, this mechanism fails. As more and more iron is absorbed, the body cannot excrete the excess. It eventually accumulates the excess iron in specific tissues in the body, especially the pancreas, liver, and heart.

How is hereditary hemochromatosis connected to genetics?

Hereditary hemochromatosis (HH) is a genetic form of hemochromatosis caused by a single gene defect. According to the National Human Genome Research Institute, the main gene, called HFE, was first identified on chromosome 6 in 1996. Most cases of HH result from a common mutation in this gene, known as C282Y. But other mutations have been identified that cause this disease, including one known as H63D. Hemochromatosis is most often inherited from both parents. If only one parent has the gene, then he or she becomes a carrier for the disease but usually does not develop it (although he or she may have a slightly elevated amount of iron in the system).

Who is likely to develop bronze diabetes in the United States?

According to the American Diabetes Association, it is thought that one in every 200 (some studies say 300) people in the United States may have both copies of the gene for hemochromatosis. Of this number, it is estimated that about half of them will eventually develop complications, including bronze diabetes. According to the Centers for Disease Control and Prevention, as many as 75 percent of patients with hemochromatosis eventually develop bronze diabetes. In the United States, it is estimated that 1 million people have hemochromatosis.

Some more recent studies also indicate that bronze diabetes may be age- and/or even gender-driven. This is because bronze diabetes is rare in children, young adults, and premenopausal women under 50, while men between the ages of 40 and 60 are more likely to be diagnosed. There may be an understandable reason that women under 50 do not develop the disease as readily as men. Women regularly lose a significant amount of blood each month through menstruation until menopause, as well as during childbirth. Because of this, they lose a significant amount of iron. For most women with the defective gene that causes hemochromatosis, the blood loss before age 50 is often enough to keep the disease-and thus possibly bronze diabetes-at bay until well after menopause.

Was there a single ancestor who began the genetic mutation for hereditary hemochromatosis?

Yes, according to many studies, the origin of hereditary hemochromatosis was most likely from a single individual in Europe around 60 to 70 generations ago. The mutation in the HFE gene in this person was passed on to subsequent generations. And because this mutant gene does not cause problems early in life-especially through the child-bearing years in women-there was no reason for the mutation to be “stopped” by natural selection as with other mutations. Thus, hemochromatosis often affects Caucasians of Northern European decent and, to a lesser extent, other ethnic groups that develop other “iron-overload” diseases.

Did writer Ernest Hemingway suffer from hemochromatosis?

Many researchers believe that American writer Ernest Hemingway (1899–1961) suffered from undiagnosed hemochromatosis, or bronze diabetes. It is thought that the disease often has a family history; for Hemingway, that appeared to be the case, as many members of his family reportedly committed suicide. (The iron accumulation plays a role in affecting mood and brain function.) Because depression and suicide are closely associated with hemochromatosis, as is the diabetes that afflicted Hemingway (along with his liver problems, heavy drinking, and high blood pressure), the disease could have been the cause of his suicide at age 61 (just weeks short of his 62nd birthday).

How do health care professionals diagnose hemochromatosis?

Diagnosing hemochromatosis purely from symptoms is difficult, as it often mimics other conditions. In addition, a person may not show any signs or symptoms until the illness has progressed to the later stages. In the early stages, the symptoms seem nonspecific, including joint pain, lack of energy, weight loss, and abdominal pain. As more iron accumulates, people may develop arthritis, problems with sexual activity, and thyroid problems, often hypothyroidism (an underactive thyroid). In the later stages, the iron accumulates first in the liver, possibly causing liver diseases such as cirrhosis. From there, it can affect the heart and pancreas, eventually often leading to heart disease and/or diabetes.

If hemochromatosis is suspected, there are several ways to diagnose the disease. One way is through a blood test to learn whether there is too much iron in the body. This is done using a transferrin saturation test or a serum ferritin test. Another way is to test for the defective gene HFE (see above for more information about this gene).

What could happen to a person with hemochromatosis if it is not treated?

According to the American Diabetes Association, if a person with hemochromatosis is not treated for the condition, it can affect the pancreas (leading to diabetes), liver (leading to cirrhosis), and heart (leading to heart disease). As with many conditions, because the symptoms for hemochromatosis resemble so many other diseases, it is thought to be severely underdiagnosed.

How is hemochromatosis treated?

The good news is that, once diagnosed, hemochromatosis is relatively simple to treat (as long as it hasn’t progressed too far). The treatments include phlebotomy, in which blood is removed from the body through a vein over multiple sessions. (On average, it is usually once or twice a week for several months, up to a year or more.) According to the National Institutes of Health, a newer treatment that includes fewer treatments than a phlebotomy is called erythrocytapheresis, in which red blood cells are separated from the whole blood, and the iron is removed.

In addition, the person’s diet can help slow down iron overload. This means avoiding iron-containing supplements and limiting intake of such iron-rich foods as red meat and especially organ meats, such as liver. Some health care professionals also suggest avoiding supplements that contain vitamin C, as that vitamin is known to increase iron absorption in the body.

What is the history behind the term “brittle diabetes”?

Brittle diabetes has often been used to describe a type of diabetes characterized by large and sudden swings in blood glucose levels. The true meaning of brittle diabetes is often debated. Some health care professionals believe it is a myth, while others believe it is a distinct condition. The concept was first mentioned in the literature in the 1940s to describe type 1 diabetics that did not respond well to insulin treatment. The biggest challenge of defining brittle diabetes was obvious. There were few ways that diabetics could easily measure their blood sugar levels, as there were no blood glucose meters or continuous blood glucose monitors. Thus, brittle diabetes became known as sudden episodes of low glucose levels (severe hypoglycemia) and recurrent, extremely high blood glucose levels (or recurrent diabetic ketoacidosis, or DKA; for more about DKA, see the chapter “Type 1 Diabetes”). Many experts believe this term was once used when a doctor did not know how to treat such extreme highs and lows of blood glucose. Today, the term is sometimes used to describe the unexplained variability of glucose levels.

In fact, with modern technology-in the form of glucose monitors and meters-it is much easier for a person with diabetes to control blood glucose levels. Thus, the number of people with so-called brittle diabetes has gone down significantly. According to some recent studies (in particular, those that included people with type 1 diabetes), life-interfering glucose fluctuations are rare, and some experts believe it is becoming even less common. The main reasons are the advancement of glucose metering and monitoring technology, better medications, and the advances in treating an individual diabetic-not only the physical but also the emotional conditions that can cause such extreme blood glucose levels.

NOT TRULY DIABETES

What has been called “type 3 diabetes”?

The term “type 3 diabetes” was introduced around 2005 as another name proposed for Alzheimer’s disease. This was suggested because of the possible connection between insulin resistance in the brain and the eventual onset of Alzheimer’s. Other recent studies indicate that Alzheimer’s is accompanied by inflammation, or the body’s response to an invading microbe (in fact, postmortem studies commonly reveal microbes in the brains of the elderly). Perhaps one day researchers will discover that inflammation and diabetes may be two of the major conditions that lead to the development of Alzheimer’s, especially since a person with type 1 or type 2 diabetes often has difficulty fighting off inflammation. But at this writing, the true reason(s) for Alzheimer’s is still highly debated.

What is Alzheimer’s disease?

Alzheimer’s disease occurs when there are nerve-cell changes in certain parts of the brain. These changes result in the death of a large number of cells, causing several symptoms that range from mild forgetfulness to serious impairments in thinking, judgment, and the ability to perform daily activities.

What is diabetes insipidus?

Diabetes insipidus (DI) is not a true form of diabetes but rather a rare disease linked to the body’s hypothalamus and pituitary gland. Similar in some symptoms to diabetes mellitus (DM), DI causes frequent urination and excessive thirst, but that is where the similarities end. Diabetes mellitus is associated with the body’s pancreas and is caused by insulin deficiency or resistance, thus leading to an imbalance in blood glucose (sugar) levels. On the other hand, DI occurs when the system that regulates the kidney’s handling of fluids is upset by certain circumstances, such as disease or trauma.

What steps lead to developing diabetes insipidus?

Diabetes insipidus occurs when the body’s fluids become unbalanced. Normally, the body balances fluid volume and composition, with the fluid intake governed by thirst and the rate of excreting urine by the production of vasopressin, also called antidiuretic hormone (ADH). This hormone is made in a small gland in the brain called the hypothalamus. The ADH is then stored in the nearby pituitary gland and released when needed into the bloodstream. When the ADH reaches the kidneys, it concentrates urine by reabsorbing some of the filtered water into the bloodstream, therefore making less urine. When this system is not working properly-in other words, when the kidneys’ ability to regulate fluids does not work well-the result is often DI.

How does a doctor test for diabetes insipidus?

Because diabetes insipidus and diabetes mellitus have a crossover of symptoms-chiefly frequent urination and excessive thirst-a health care provider may suspect that a person with DI actually has diabetes mellitus. Therefore, testing is needed to distinguish the difference, including urinalysis (to determine the concentration of a person’s urine) and a fluid-deprivation test (which will change body weight, urine output, and urine concentration when fluids are withheld, all of which can be used to learn whether there is any defect in ADH production or the kidneys’ response to ADH).

What are the various forms of diabetes insipidus (DI)?

There are several different forms of diabetes insipidus. The following lists some of these forms and the factors that explain the differences:

Central DI-This is the most common form of DI. It is caused by damage to the pituitary gland, which stops the normal storage and release of ADH (antidiuretic hormone). Damages to the pituitary gland can be caused by a variety of diseases, head injuries, neurosurgery, or even genetic disorders.

Nephrogenic DI-This is caused by a disruption in the kidneys’ ability to respond to ADH. The disruption can be caused by various drugs (lithium, for example) or by several types of chronic diseases, such as sickle-cell disease, inherited genetic disorders, kidney failure, or partial blockage of the ureters. It is often treated with several drugs, including hydrochlorothiazide.

Dipsogenic DI-This is caused by an actual defect in or damage to the body’s thirst mechanism, which is located in the brain’s hypothalamus. Abnormal increase in thirst and fluid intake are seen in a person with this problem, and those, in turn, suppress ADH secretion-and increase the urine output. So far, there is no real treatment for dipsogenic DI. (For more about ureters and the urinary system, see the chapter “How Diabetes Affects the Urinary System.”)

Gestational DI-Similar to gestational diabetes, gestational DI occurs only during pregnancy, but that is where the similarity ends. Gestational DI results when a specific enzyme made by the placenta destroys the ADH in the mother. (The placenta is the system of tissues and blood vessels that develop with the fetus; it is attached to the mother, supplying nutrients and eliminating waste products between the fetus and mother.) It is most often treated with desmopressin (although there is a rare form of gestational DI, in which the thirst mechanism is abnormal, which is not treated with desmopressin).

What is “uric acid diabetes”?

According to a recent study, there may be a connection between uric acid and how the body metabolizes carbohydrates and fats (lipids). The researchers suggested the phrase “uric acid diabetes” after discovering a statistically high incidence of diabetes in people with hyperuricemia (an abnormally high amount of uric acid in the blood), gout, or both. But more studies need to be conducted to verify whether there truly is a uric acid–diabetes connection. (For more about uric acid, see the chapter “How Diabetes Affects the Urinary System.”)