Diabetes mellitus: Nursing pathophysiology

Diabetes. Mellitus is a group of endocrine disorders characterized by hyperglycemia or elevated blood glucose.

The two main types are type one diabetes, which is caused by an absolute insulin deficiency and type two diabetes which is caused by insulin resistance.

Ok. So the pancreas is an organ located in the abdomen that plays a role in glucose regulation and digestion scattered throughout the pancreas are small clusters of cells called islets of Langerhans.

Among these cells are alpha cells and beta cells. The alpha cells secrete glucagon in response to decreasing blood glucose, glucagon increases blood glucose by stimulating the liver to break down glycogen or stored glucose by a process called glycogenolysis.

Conversely, beta cells secrete insulin in response to increasing blood glucose, insulin lowers blood glucose which also suppresses alpha cell secretion of glucagon along with insulin beta cells, cosecrete amylin which prevents post prandial or post meal spikes in blood glucose by inhibiting gastric emptying, increasing satiety and suppressing glucagon release.

Now, for cells to function, they need glucose as a source of energy. However, cell membranes are impermeable to glucose.

So for glucose to get inside the cell, insulin must first bind to insulin receptors on the cell membrane. This binding activates the cell's glucose transporters that will then facilitate the movement of glucose into the cell.

Type. One, diabetes is most commonly caused by an autoimmune destruction of beta cells resulting in an inability to produce insulin.

In other cases, the cause is idiopathic meaning there is no known cause risk factors include exposure to certain viruses and a family history of type one diabetes.

As for type two diabetes, the main cause is insulin resistance in the tissues, which is when cells don't respond as easily to insulin.

Risk factors include obesity, physical inactivity and a diet high in simple carbohydrates, saturated fats and red meat. Additionally, those older than 65 years and those with a history of hypertension are at increased risk.

All right now, with type one diabetes, a lack of insulin means glucose can't enter the cells and without glucose, the cells begin to starve.

Additionally, alpha cells will continue to secrete glucagon because they become less responsive to high levels of glucose.

So the liver continues to break down glycogen into glucose which contributes to a further increase in blood glucose resulting in hyperglycemia.

On the other hand, with type two diabetes, cells in the tissues become insulin resistant and additional insulin is required to get glucose to enter the cells.

The beta cells respond by releasing more insulin over time. However, it becomes more difficult for the beta cells to keep up with the demand.

They become exhausted, dysfunctional and progressively lose their ability to produce enough insulin to overcome resistance.

Eventually beta cells begin to undergo apoptosis or cell death. Leaving less beta cells available to produce insulin.

Losing beta cells means less insulin and less insulin means glucose will build up in the blood, resulting in hyperglycemia.

Now sustained hyperglycemia has detrimental effects on the rest of the body. The kidneys reach the maximum amount of glucose they can reabsorb.

So extra glucose spills into the urine causing glycosuria. Additionally, since glucose is osmotically active glyco urea is accompanied by a large amount of water in the urine.

Glucose also pulls water out of cells and into the bloodstream, expanding the blood volume and leaving the cells dehydrated over time.

Hyperglycemia causes structural damage to the blood vessels, damage to the macro vasculature or large blood vessels like arteries in the heart brain and periphery accelerates atherosclerosis, increasing the risk of heart disease, stroke and peripheral artery disease damage to the microvasculature or small arterioles.

And capillaries primarily involves thickening of the basement membrane of the small vessels in the eyes and kidneys in the retina.

This increases the risk of diabetic retinopathy leading to vision impairment and blindness and glomerular damage in the kidneys.

Results in diabetic nephropathy which can eventually lead to kidney failure. Chronic hyperglycemia can also cause nerve damage called diabetic neuropathy, which involves damage to the myelin sheath that protects nerves and promotes transmission of electrical impulses.

This damage causes both autonomic and sensory dysfunction. Autonomic dysfunction can cause problems like postural hypotension, bladder dysfunction, tachycardia and sexual problems like erectile dysfunction.

Sensory dysfunction can cause numbness, tingling and pain. Commonly in the hands and feet.

Neuropathy can combine with poor circulation from vascular damage and lead to complications like diabetic foot ulcers, impaired healing even after minor trauma and even amputations.

On top of that infections like urinary tract infections and soft tissue infections are more common with diabetes because hyperglycemia weakens the immune system and decreases blood supply which impairs delivery of immune cells.

Additionally, the extra glucose serves as an energy source for certain microorganisms allowing them to proliferate more than normal.

Ok. So, clinical manifestations of diabetes are related to hyperglycemia and depend on its severity and duration.

Generally, symptoms include the three P's polyphagia, polyuria and polydipsia polyphagia or excessive hunger occurs as the cells starve and the brain responds by inducing eating behaviors.

Polyuria or excessive urination occurs as the extra fluid filters through the kidneys and polydipsia or excessive thirst occurs because of cellular dehydration and extensive fluid loss from polyuria, blood glucose levels will be elevated as well as the hemoglobin A1C, which measures the average blood glucose level over the previous three months upon urinalysis, glyco urea can be seen as the kidneys eliminate excess glucose.

Microalbuminuria may also be present as increased vascular permeability in the damaged kidneys allows proteins to spill into the urine.

Hypertension may develop due to systemic atherosclerosis and inappropriate activation of the renin angiotensin aldosterone system by the kidneys.

Other clinical manifestations can include fatigue, blurry, vision and unintended weight loss. All right.

As a quick recap diabetes. Mellitus is a group of endocrine disorders characterized by hyperglycemia.

Type one diabetes involves destruction of pancreatic beta cells causing absolute insulin deficiency. While type two diabetes involves insulin resistance.

Generally, clinical manifestations are related to hyperglycemia, its severity and duration. But typically include polyphagia, polyuria, and polydipsia.