What is the primary difference between Type 1 and Type 2 Diabetes Mellitus?

The fundamental difference lies in their etiology and pathophysiology. Type 1 Diabetes is an autoimmune condition where the body's immune system mistakenly destroys the insulin-producing beta cells in the pancreas, leading to an absolute deficiency of insulin. Patients require exogenous insulin for survival. Type 2 Diabetes, on the other hand, is characterized by insulin resistance (cells don't respond effectively to insulin) and a progressive decline in beta-cell function, resulting in relative insulin deficiency. It's often associated with lifestyle factors like obesity and physical inactivity, and while insulin may eventually be needed, it's not typically the initial treatment.

Why do people with diabetes experience increased thirst and frequent urination?

These symptoms, known as polydipsia and polyuria respectively, are direct consequences of hyperglycemia. When blood glucose levels are very high, the kidneys cannot reabsorb all the glucose, leading to its excretion in urine (glycosuria). Glucose is an osmotically active substance, meaning it draws water with it. This increased water excretion in urine leads to excessive fluid loss (polyuria) and subsequent dehydration. The body's response to dehydration is to trigger thirst, prompting increased fluid intake (polydipsia) to compensate for the fluid loss.

What is HbA1c, and why is it important for diabetes management?

HbA1c, or glycated hemoglobin, is a blood test that measures the average blood glucose levels over the past 2-3 months. When glucose is present in the blood, it binds to hemoglobin in red blood cells. The more glucose in the blood, the more hemoglobin gets glycated. Since red blood cells live for about 3 months, HbA1c provides a long-term picture of glucose control, unlike a single fasting or random glucose reading. It's crucial for diagnosing diabetes, monitoring treatment effectiveness, and assessing the risk of developing diabetes complications.

Can diabetes be cured?

Currently, there is no definitive cure for Type 1 Diabetes; it requires lifelong insulin therapy. For Type 2 Diabetes, while it cannot be 'cured' in the traditional sense, it can often be managed very effectively, and in some cases, even put into remission, especially with significant lifestyle changes like substantial weight loss and dietary modifications. Remission means blood glucose levels return to normal without medication. However, the underlying predisposition remains, and careful monitoring is still necessary to prevent recurrence. Gestational diabetes usually resolves after pregnancy, but it increases the risk of developing Type 2 diabetes later.

What are the major long-term complications of uncontrolled diabetes?

Uncontrolled, chronic hyperglycemia damages blood vessels throughout the body, leading to a range of severe long-term complications. These include microvascular complications like diabetic retinopathy (damage to eye blood vessels, leading to blindness), diabetic nephropathy (kidney damage, leading to kidney failure), and diabetic neuropathy (nerve damage, causing pain, numbness, and organ dysfunction). Macrovascular complications involve larger blood vessels, increasing the risk of cardiovascular diseases such as heart attacks, strokes, and peripheral artery disease, which can lead to amputations. Early and consistent glucose control is vital to prevent or delay these complications.

How does insulin resistance develop in Type 2 Diabetes?

Insulin resistance is a complex phenomenon where cells in the body, particularly muscle, fat, and liver cells, do not respond effectively to insulin. This means that even when insulin is present, glucose uptake into cells is impaired, and the liver continues to produce glucose. The exact mechanisms are multifactorial, involving genetic predispositions, chronic inflammation, and lifestyle factors. Obesity, especially visceral fat accumulation, plays a significant role as adipose tissue releases inflammatory cytokines and free fatty acids that interfere with insulin signaling pathways. Over time, this chronic resistance leads to beta-cell exhaustion as the pancreas tries to compensate by overproducing insulin.

Diabetes Mellitus

Biology

NEET UG

Version 1Updated 22 Mar 2026

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Diabetes Mellitus (DM) is a chronic metabolic disorder characterized by sustained hyperglycemia, resulting from defects in insulin secretion, insulin action, or both. Insulin, a hormone produced by the beta cells of the pancreatic islets of Langerhans, is crucial for regulating blood glucose levels by facilitating glucose uptake into cells and inhibiting glucose production by the liver. When insul…

Quick Summary

Diabetes Mellitus is a chronic condition marked by high blood sugar (hyperglycemia) due to problems with insulin, a hormone from the pancreas. Insulin helps glucose enter cells for energy. In Type 1 Diabetes, the body's immune system destroys insulin-producing cells, leading to absolute insulin deficiency, requiring lifelong insulin injections.

Type 2 Diabetes, more common, involves insulin resistance (cells don't respond well to insulin) and/or insufficient insulin production. It's often linked to lifestyle and genetics. Gestational Diabetes occurs during pregnancy.

Common symptoms include increased urination (polyuria), thirst (polydipsia), and hunger (polyphagia). Diagnosis involves blood tests like Fasting Plasma Glucose, Oral Glucose Tolerance Test, and HbA1c.

Untreated diabetes can lead to severe complications affecting eyes, kidneys, nerves, and heart. Management focuses on lifestyle changes and medications, including insulin or oral hypoglycemic agents, to maintain blood glucose levels within a healthy range and prevent long-term damage.

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Diabetes Mellitus (DM): — Chronic hyperglycemia.

Types: — Type 1 (T1DM), Type 2 (T2DM), Gestational (GDM).

T1DM: — Autoimmune destruction of pancreatic beta cells → absolute insulin deficiency.

T2DM: — Insulin resistance + progressive beta-cell dysfunction → relative insulin deficiency.

Insulin: — Lowers blood glucose, promotes glucose uptake, glycogenesis.

Glucagon: — Raises blood glucose, promotes glycogenolysis, gluconeogenesis.

Symptoms (3 Ps): — Polyuria, Polydipsia, Polyphagia, Weight loss (T1DM).

Diagnostic Criteria:

- FPG $ge 126,\text{mg/dL}$ - 2-hr OGTT $ge 200,\text{mg/dL}$ - HbA1c $ge 6.5%$ - Random PG $ge 200,\text{mg/dL}$ (with symptoms)

Microvascular Complications: — Retinopathy, Nephropathy, Neuropathy.

Macrovascular Complications: — CAD, Stroke, PAD.

Metformin: — Reduces hepatic glucose production, improves insulin sensitivity.

3 Ps of Diabetes:

Pee a lot (Polyuria) Prinkly (Polydipsia - very thirsty) People (Polyphagia - very hungry)

T1DM vs T2DM - 'A' for Absolute, 'R' for Resistance:

T1DM: Autoimmune, Absolute insulin deficiency, Always needs insulin. T2DM: Resistance to insulin, Relative insulin deficiency, Related to lifestyle.