Uncommon Causes of High Blood Glucose

Many people assume that high blood glucose levels occur only in individuals with diabetes. However, there are other more unusual causes of high glucose levels in the blood (also called hyperglycemia).

Primary causes of hyperglycemia do include type I and type II diabetes mellitus. Type I diabetes results solely from lack of insulin secretion due to pancreatic B-cell destruction. Type II diabetes, in contrast, involves an element of insulin resistance. Secondary causes of hyperglycemia result from non-diabetic insulin resistance, toxins, pancreatic diseases and endocrine dysfunction.

Insulin resistance may occur due to obesity, lack of exercise, cirrhosis of the liver, and/or stress. Cirrhosis of the liver is often accompanied by jaundice (yellowing of the skin), ascites (fluid collection in the belly), splenomegaly (enlarged spleen), spider angiomata (small vessels become visible on chest and face), and other physical exam findings.

Toxins that can cause elevated blood sugar include alcohol, prescription medications and the metal cadmium. Cigarettes are a significant source of cadmium. Research shows that cigarette smokers have higher levels of cadmium. An individual smoker will consume varying levels of cadmium depending on cigarette brand and filtered vs non-filtered cigarettes.

Diseases of the exocrine pancreas that can cause high blood glucose include a hereditary condition called hemochromatosis as well as pancreatic cancer. Hemochromatosis causes iron excess in the body. This then causes hyperglycemia due to the toxicity of iron to insulin-producing pancreatic B-cells. Hemochromatosis is often asymptomatic when detected on routine exams. If the disease has progressed to the point of causing hyperglycemia other symptoms may be expected including fatigue, cirrhosis, skin pigmentation, cardiomyopathy, arthropathy (usually the hands) and/or hypogonadism.

Pancreatic tumors may cause hyperglycemia. Commonly presenting symptoms of pancreatic cancer include jaundice, mid-abdominal pain radiating to the back, steatorrhea (fatty diarrhea), and anorexia (loss of appetite) and weight loss.

Several forms of endocrine dysfunction may cause hyperglycemia, including acromegaly, hyperthyroidism, hypercortisolism and pheochromocytomas. Excess growth hormone can cause a condition called acromegaly. Excess levels of growth hormone causes high blood sugar, enlargement of peripheral body parts, arthralgias and even gout.

Hypercortisolism may be caused by corticosteroid medications or by endocrine gland tumors or dysfunction. Hypercortisolism often presents with a Cushingoid picture. A Cushingoid person may have purple striae (stretch marks on belly), moon-facies (round-shaped face) and/or buffalo's hump (fatty hump between upper shoulders).

Pheochromocytoma, an adrenal gland tumor, would present with paroxysmal attacks of hypertension, headache, hyperhidrosis (excess sweating), heart palpitations and anxiety. Hyperthyroidism would share many of these same symptoms: palpitations, sweating, anxiety and may additionally have signs such as enlarged thyroid, exophthalmos (bulging eyes) and, rarely, pretibial myxedema (waxy, non-pitting edema of the anterior lower legs).

Glucose toxicity is an interesting phenomenon which can contribute to high blood glucose in some individuals. Glucose toxicity is the condition in which initial hyperglycemia, resulting from any cause, may itself cause further high glucose levels by decreasing insulin sensitivity and increasing glucose production in the liver.

High blood glucose can be caused by many conditions other than Type 1 or 2 Diabetes mellitus. However, Type 2 diabetes is the most common cause of hyperglycemia in adults in the United States. The incidence of Type 2 diabetes in children is also, unfortunately, on the rise.