Diabetes Mellitus

A chronic metabolic disease in which blood glucose remains persistently high due to abnormalities in insulin secretion or action, classified into type 1, type 2, and gestational diabetes, etc.

Diabetes Mellitus

Overview

Diabetes mellitus (糖尿病, Diabetes Mellitus) is a chronic metabolic disease in which, due to insufficient insulin secretion or insulin resistance, glucose in the blood is not properly absorbed into cells, resulting in persistent hyperglycemia. It is one of the fastest-growing non-communicable diseases worldwide; according to the International Diabetes Federation (IDF) in 2021, approximately 537 million adults are estimated to have diabetes. Without active blood glucose control and lifestyle management, it can lead to serious complications such as cardiovascular disease, kidney disease, blindness, and foot amputation.

Main Content

Definition and Classification

Diabetes is broadly classified into four types according to cause and pathophysiology.

Type 1 diabetes: A form in which pancreatic beta cells are destroyed by an autoimmune mechanism, resulting in almost no insulin production; it mainly develops in childhood and adolescence. It accounts for about 5–10% of all diabetes cases and requires lifelong insulin injections.
Type 2 diabetes: A form characterized by both insulin resistance and relative insulin secretion deficiency, accounting for more than 90% of all cases. Major risk factors include obesity, advanced age, genetic factors, lack of exercise, and high-calorie diet.
Gestational diabetes: Glucose intolerance first detected during pregnancy, occurring in about 7–10% of pregnant women. It often normalizes after delivery, but the risk of subsequently developing type 2 diabetes is greatly increased.
Other specific types: This includes secondary diabetes caused by pancreatitis, pancreatectomy, endocrine diseases, or drugs (such as steroids).

Pathophysiology

Normal blood glucose regulation is achieved by the balance between insulin secreted by beta cells and glucagon secreted by alpha cells in the pancreatic islets of Langerhans. Insulin promotes glucose uptake by muscle and fat cells and suppresses hepatic gluconeogenesis. In diabetes, this signaling is impaired, causing fasting and postprandial blood glucose to rise, and glucose is excreted in the urine, leading to osmotic diuresis and the typical 'three polys' symptoms—polydipsia, polyuria, and polyphagia—along with weight loss.

Symptoms and Diagnosis

In the early stages, it is often asymptomatic, so regular checkups are important. The diagnostic criteria are as follows.

Fasting blood glucose ≥ 126 mg/dL
2-hour blood glucose on oral glucose tolerance test (OGTT) ≥ 200 mg/dL
Glycated hemoglobin (HbA1c) ≥ 6.5%
Random blood glucose ≥ 200 mg/dL along with typical symptoms of diabetes

If any one of the above criteria is met, diabetes is diagnosed, and repeat testing is performed for confirmation. Fasting blood glucose of 100–125 mg/dL is classified as impaired fasting glucose, and a 2-hour OGTT blood glucose of 140–199 mg/dL as impaired glucose tolerance; collectively, these are called 'prediabetes.'

Complications

Complications are divided into acute and chronic.

Acute: Diabetic ketoacidosis (DKA), hyperglycemic hyperosmolar syndrome, hypoglycemia
Chronic microvascular complications: Diabetic retinopathy, nephropathy, neuropathy
Chronic macrovascular complications: Coronary artery disease, stroke, peripheral artery disease
Other: Diabetic foot (foot ulcers and amputation), increased susceptibility to infection, periodontal disease, depression

Treatment and Management

The core of treatment is integrated management of blood glucose, blood pressure, and lipids.

1. Lifestyle therapy: Balanced diet, regular aerobic and resistance exercise (at least 150 minutes per week), smoking cessation, moderation in alcohol, weight loss (5–10%)

2. Pharmacotherapy: Metformin is used as the first-line agent, and SGLT2 inhibitors, DPP-4 inhibitors, GLP-1 receptor agonists, sulfonylureas, insulin, etc. are combined as needed.

3. Self-management education: Education on self-monitoring of blood glucose, foot care, and management of hypoglycemia is essential.

4. Regular checkups: HbA1c every 3–6 months, and fundus examination and microalbuminuria test at least once a year.

Latest Trends (2024-2025)

Expansion of GLP-1 receptor agonists: Semaglutide, tirzepatide, etc. have been proven not only to improve blood glucose but also to reduce weight and provide cardiovascular and renal protection, and are widely prescribed as obesity treatments. Since 2024, development of oral GLP-1 agents has been accelerating.
Popularization of continuous glucose monitoring (CGM): CGM, which allows real-time blood glucose data to be checked on a smartphone, is being expanded in insurance coverage not only for type 1 but also for type 2 diabetes patients, and the concept of Time in Range (TIR) has become established as a new blood glucose management indicator.
Automated insulin delivery (AID) systems: 'Artificial pancreas' technology, which connects CGM and an insulin pump via an algorithm, has been commercialized and is showing effects in reducing nocturnal hypoglycemia and improving blood glucose control.
Digital health and AI: Blood glucose prediction algorithms, AI for automated reading of diabetic retinopathy, and telemedicine-based management platforms are spreading.
Regenerative medicine: Stem cell-derived beta cell transplantation and encapsulated cell therapy are in clinical trial stages as fundamental treatment alternatives for type 1 diabetes.
Domestic status: According to the Korean Diabetes Association, the prevalence of diabetes among adults aged 30 and older has exceeded about 16%, and including the prediabetes population, it reaches about 40% of adults. Accordingly, the importance of the national screening system and chronic disease management programs is being emphasized.