Diabetes in Disguise: When other medical conditions mimic or cause the disease

With all of the media coverage type 2 diabetes has received in recent years, most people know that the disease is very common.

The most prevalent form of the condition, type 2 diabetes is caused by a combination of factors, including insulin resistance, a condition in which the body’s muscle, fat and liver cells do not use insulin effectively, added to by an inability, over time, to produce enough insulin to compensate for the body’s impaired ability to use insulin.

There are a number of risk factors for type 2 diabetes, among them a family history of the disease, older age, sedentary lifestyle, overweight/obesity and being of a certain racial/ethnic background (Native American, Hispanic, African American, Southeast Asian). In women, having a prior diagnosis of PCOS (polycystic ovarian syndrome) or a history of gestational diabetes (diabetes in pregnancy) are also risk factors

In some instances, however, there may be a separate reason altogether that plays a part in the onset of diabetes.

For example, certain medications can increase blood sugars. The most common of these drugs are steroids (causing a condition referred to as “Cushing’s syndrome”) that are often used to reduce inflammation in lung diseases such as asthma and emphysema and for rheumatologic conditions like arthritis, and creams/lotions applied to the skin for the treatment of skin conditions such as eczema and psoriasis. Short-term use of these medications may not cause problems, but when use is frequent or extended it can cause insulin resistance and may result in permanent type 2 diabetes that can be difficult to treat.

A second offending class of drugs is medications used for psychiatric illness, specifically drugs used to manage psychosis, a mental disorder characterized by a disconnection from reality. Often these drugs are necessary to manage serious symptoms of the condition, and the resulting diabetes must simply be treated if it occurs. However, alternatives sometimes can be found that control the symptoms, but don’t increase the risk for development or worsening of diabetes.

Other less common but essential medications that can cause or worsen diabetes are drugs used to prevent rejection of a kidney, liver or heart transplant and medications used to treat HIV infections.

Among medical conditions that may causes diabetes is a rare hormonal disorder called Cushing’s disease. Cushing’s occurs when the pituitary, the master hormone gland located in the brain, produces and secretes too much of a hormone called ACTH. The ACTH in turn signals the two adrenal glands, located above the kidneys, to make extra cortisol. Known as the “stress” hormone, cortisol’s function is to maintain the body’s blood pressure and blood sugar in the appropriate range for everyday needs (see related story on page 20). When excess cortisol is produced, patients can experience increased or worsening blood sugar, bone fractures and high blood pressure.

It may be difficult to tell the difference between Cushing’s and common obesity. Cushing’s patients typically gain weight, develop fatty deposits behind the neck or above the collar bones and encounter wide, purple stretch marks on their skin. The disease also causes thinning skin that manifests as easy bruising and thinned musculature in the arms and legs that appears as muscle weakness. Treatment includes surgery and/or medication. Diabetes may resolve with treatment of Cushing’s, but the condition is complex, and associated illnesses such as diabetes should be followed closely.

Another rare hormonal disorder that causes high blood sugar is acromegaly, which literally means “big fingers.” Acromegaly occurs when the body produces excess growth hormone due to a growth in the pituitary gland. The bones of the body may grow along with the soft tissues and even the internal organs over a long period of time in acromegaly. This typically is such a slow process that patients, or even more often their family members and doctor, don’t notice changes until years after the original onset of signs and symptoms. Beyond diabetes, which often is the first problem identified in these patients, the person with acromegaly is at risk for arthritis, high blood pressure, heart disease, sleep apnea, fertility problems, growths in the large intestine (colonic polyps) and thyroid issues such as thyroid nodules. Treatment generally includes pituitary surgery and may include drugs such as somatostatin, which can make diabetes worse or more difficult to manage.

Chronic pancreatitis (repetitive injury to the pancreas from inflammation and subsequent scarring) can occur from alcohol abuse, gallstones, abnormal development in the organ’s structure (anatomic malformation) and other causes. Since the pancreas is the body’s insulin factory, when most of it is affected by disease, the patient can develop high sugars.

A rare genetic disorder known as hemochromatosis may also cause diabetes when the pancreas is involved. Hemochromatosis causes the body to absorb too much iron from food, which is deposited in internal organs.

As you can see, there are a number of conditions and circumstances which may lead to diabetes. They usually cause a variety of other signs and symptoms that are troubling to the patient and are warning signals for the physician, who then refers to the appropriate specialist to address the problem. An endocrinologist, a specialist in hormonal disease, will be able to help identify the cause and will understand the influence of other diseases and drugs on your blood glucose.

Dr. Dustin Higgins graduated from Brigham Young University with a degree in Molecular Biology and went on to the National Institutes of Health to conduct a year of research in the genetics of type 2 diabetes. He attended medical school at Midwestern University and completed his residency at Mercy Hospital in St. Louis. He is an Endocrinology fellow with the Division of Endocrinology, Metabolism and Lipid Research at Washington University School of Medicine in St. Louis, where he is conducting clinical research in type 2 diabetes. He is currently studying the role of phospholipids in the pathogenesis of insulin resistance and the metabolic syndrome.

Dr. Elina Trofimovsky is a senior Fellow at the Mount Sinai Hospital Division of Endocrinology, Diabetes and Bone Diseases. She is a graduate of SUNY Downstate Medical School, after which she completed her internal medicine residency training at Hofstra-NSLIJ. Dr. Trofimovsky plans to practice general endocrinology in Connecticut after graduating from fellowship.