Complications of Diabetes

Diabetes mellitus is a chronic, multisystem disease characterized by high blood glucose, or hyperglycemia, which can lead to both acute and chronic complications.

Okay, let’s review the pathophysiology of hyperglycemia. Normally, the beta cells in the pancreas release insulin, which is a hormone that helps glucose move from the bloodstream and into the tissue cells where it can be used for energy.

In diabetes, though, either the pancreas doesn't produce insulin, like with type 1 diabetes, or the body’s cells are resistant to insulin, like with type 2 diabetes.

Either way, hyperglycemia results, causing symptoms like polyuria, or frequent urination; polydipsia, or increased thirst; and polyphagia, or increased appetite.

Now, hyperglycemia can cause two serious acute complications: diabetes-related ketoacidosis, or DKA, and hyperosmolar hyperglycemia syndrome, or HHS.

First, in DKA, glucose levels rise to 250 mg/dL or more, but since the cells are unable to use the glucose, they start breaking down adipose tissue, or fat, as a source of energy; a process called lipolysis. During lipolysis, ketone bodies are made as a byproduct, which increases the acidity of the blood, leading to metabolic acidosis.

This manifests as deep and labored breathing, also called Kussmaul respirations, and fruity-smelling breath. As excess glucose is eliminated by the kidneys, large amounts of water is pulled along with it, a process called osmotic diuresis. Dehydration and electrolyte imbalances develop as fluids are depleted.

On the other hand, in HHS, glucose levels rise to 600 mg/dL or more. This results in osmotic diuresis and dehydration that is much more severe than with DKA. But in contrast to DKA, there’s no breakdown of fat, so metabolic acidosis does not occur.

If untreated, DKA and HHS can progress to cerebral edema, coma, and even death.

Now, another acute complication is caused by hypoglycemia, or low glucose levels. Hypoglycemia can occur when there’s an imbalance between insulin and glucose, like when a patient doesn't eat enough, exercises more than usual, or takes too much insulin or antidiabetic medication.

When glucose drops below 70 mg/dL, the body reacts by releasing counterregulatory hormones such as glucagon and cortisol to increase the glucose level; and epinephrine, which activates the autonomic nervous system resulting in shakiness, diaphoresis, palpitations, and anxiety.

Other clinical manifestations are related to a decreased glucose supply to the brain and include blurred vision and confusion.