This lesson will discuss hyperglycemia, hypoglycemia, and glucosuria as well as the major causes for each one of these test results. This means we'll touch base upon endocrine diseases, such as Cushing's and diabetes mellitus.
The Pros and Cons of Sugar
Sugar is such a wonderful and terrible thing at the same time. It makes things taste good but gives us cavities. It gives us energy but can also make us fat. It's a contrast of a lot of highs and lows.
These highs and lows are actually monitored in our body through blood tests. High and lows could actually be significant indicators of important diseases, as you'll soon find out.
Hyperglycemia and Hypoglycemia
When your doctor orders a blood test or if you perform a quick one at home, one of the values that is measured is glucose. Glucose is a carbohydrate, a simple sugar (or monosaccharide, to be precise), that is an important fuel for energetic processes within our body. It's essentially like the gasoline you pump into your car every week. The gasoline is a fuel for energetic processes that make your car run. With no gas, you're not going anywhere.
The normal level of glucose in the blood, based on a fasting sample, is approximately 70-100 mg/dL. Increased levels of glucose in the blood are termed hyperglycemia, whereas decreased levels of glucose in the blood are termed hypoglycemia. They both sound similar, but by definition they're anything but. Each term has a suffix of '-emia,' which references the blood. 'Hyper-' is a prefix that implies an excess or abnormal increase in something. In contrast, 'hypo-' implies an inadequate amount of something or an abnormally low amount. The '-glyc-' refers to something sweet, and we know how sweet sugar is!
It's easy to remember which of the two, 'hyper' or 'hypo,' is related to an increase or a decrease in something. If you have a hyper puppy or a hyper brother or a hyper daughter, that means they are buzzing around like crazy due to their high energy levels, which in turn may be due to too much sugar intake. Therefore, 'hyper' refers to an abnormally high value of something. By default then, 'hypo' is the exact opposite.
Causes of Hyperglycemia
If a blood test reveals hyperglycemia, it could be as a result of many different things. Let's examine some of these.
Diabetes mellitus is a very famous cause of hyperglycemia. People with diabetes mellitus are either deficient in or resistant to a hormone called insulin. Insulin helps to drive glucose from the blood and into the cells that make up your body. Logically, if insulin is either not present or is ineffective, the glucose just stays in the blood in abnormally high levels, resulting in hyperglycemia.
Another cause of hyperglycemia is stress. Yep. Stress can cause elevations in blood glucose. There's more than one reason for this. For instance, stress releases hormones such as cortisol and epinephrine that promote increases in glucose formation (called gluconeogenesis) and glycogen breakdown (called glycogenolysis), respectively, in the liver. Glycogen is like a big sugar cube from which little glucose crystals can be broken off of and sent into circulation as needed.
Additionally, inflammatory molecules in cases of stress due to injury actually promote insulin resistance, which further increases the levels of glucose in the blood. Do note that, as a general rule, stress causes transient, or short-lived, episodes of hyperglycemia in contrast to uncontrolled diabetes.
The reason I started off with mentioning stress is actually because of the fact that I wanted to emphasize that cortisol, a type of steroid called a glucocorticoid, promotes glucose formation. Levels of cortisol rise in something known as Cushing's disease, a form of Cushing's syndrome. Cushing's disease, therefore, causes hypercortisolism. And you already know what that means: high blood sugar!
Another cause of Cushing's syndrome is the administration of glucocorticoids for medical purposes. These, for reasons that should be clear to you by now, cause elevations in blood sugar as well.
Causes of Hypoglycemia
The other side of the coin to all of this is hypoglycemia. Hypoglycemia may be a result of starvation. So you're literally just not getting enough into your system, and your gas tank is, therefore, running on empty.
The use of insulin therapy can lower blood sugar, and an insulin-secreting tumor, known as an insulinoma, can accomplish the same feat.
Severe liver disease can also cause hypoglycemia. Remember that I said that glycogenolysis and gluconeogenesis occur in the liver? Everything should be coming full circle for you now in understanding hypoglycemia. If your liver is spent, your glucose-producing factory is useless, and you become hypoglycemic.
Causes of Glycosuria
Now, before I end this lesson, I want to go over the important concept of finding glucose in the urine. Urinalysis, the measurement of different values in the urine, is as important of a tool in diagnosing many conditions as blood work is.
Under normal conditions, very little to no glucose should be found in the urine. While the kidneys do filter glucose out of the blood, they should reabsorb virtually all of it back into circulation before the filtered blood, now called urine, enters your bladder.
Therefore, glycosuria, aka glucosuria, is a condition where excessive glucose is excreted in the urine.
A urine dipstick test is often used to measure the increases of glucose in the urine. I'm sure you've seen the urine test strips before; they are the ones with all the pretty colors on a little strip of paper. Each color change will be indicative of ever-increasing amounts of glucose in the urine.
The main reason for elevations of glucose in the urine is, not surprisingly, diabetes mellitus. This disease causes such overwhelming hyperglycemia that the kidney's capacity to reabsorb the filtered glucose (a maximum of about 180 mg/dL) is breached, leading to glucose excretion in the urine.
Think about this. The kidneys are supposed to reabsorb glucose, like a sponge absorbs water. But if the capacity of the sponge is overwhelmed with too much water, you can pour as much water onto it, but the sponge just won't hold anymore, and the water will simply drip out of the sponge and into the sink. The exact same thing happens with kidneys that are overwhelmed with too much glucose, breaching what's known as the renal threshold of glucose.
Another, albeit less likely, possibility for glucosuria is called renal glucosuria. This is when the kidneys, despite normal or low levels of glucose in the blood, are unable to reabsorb glucose, leading to its excretion in the urine. This may occur as a result of an inherited genetic defect.
The main concepts we learned in this lesson were:
Hyperglycemia, or increased levels of glucose in the blood. This can occur due to diabetes mellitus, Cushing's syndrome, stress, and much more.
In contrast, decreased levels of glucose in the blood are termed hypoglycemia and may be a result of starvation, liver disease, or a tumor called an insulinoma.
Finally, glycosuria, aka glucosuria, is a condition where excessive glucose is excreted in the urine. This is most commonly a result of diabetes mellitus or, in rare cases, a condition known as renal glucosuria.
Once you get to the end of this lesson, you could be able to:
- Note the good and bad effects of sugar
- Compare hypoglycemia and hyperglycemia and describe the possible causes of each
- Define glycosuria and list some of its potential causes