From the Guidelines
Diabetes mellitus can be classified into four main categories: Type 1 diabetes, Type 2 diabetes, Specific types of diabetes due to other causes, and Gestational diabetes mellitus. According to the most recent guidelines 1, these categories are defined as follows:
- Type 1 diabetes: due to autoimmune b-cell destruction, usually leading to absolute insulin deficiency, including latent autoimmune diabetes of adulthood
- Type 2 diabetes: due to a non-autoimmune progressive loss of adequate b-cell insulin secretion frequently on the background of insulin resistance and metabolic syndrome
- Specific types of diabetes: due to other causes, e.g., monogenic diabetes syndromes, diseases of the exocrine pancreas, and drug- or chemical-induced diabetes
- Gestational diabetes mellitus: diabetes diagnosed in the second or third trimester of pregnancy that was not clearly overt diabetes prior to gestation
It is essential to note that classification is crucial for determining therapy, but some individuals cannot be clearly classified as having type 1 or type 2 diabetes at the time of diagnosis 1. The traditional paradigms of type 2 diabetes occurring only in adults and type 1 diabetes only in children are no longer accurate, as both diseases occur in both age-groups. Early diagnosis and appropriate management are essential for all types to prevent serious complications like cardiovascular disease, neuropathy, nephropathy, and retinopathy.
The management of these types may involve lifestyle modifications, oral medications like metformin, and sometimes insulin. The American Diabetes Association (ADA) position statement “Diagnosis and Classification of Diabetes Mellitus” provides additional information on the classification and diagnosis of diabetes 1.
In clinical practice, it is crucial to consider the heterogeneity of type 1 and type 2 diabetes, as clinical presentation and disease progression may vary considerably 1. By understanding the different types of diabetes and their characteristics, healthcare providers can provide personalized care and management plans to improve patient outcomes and quality of life.
From the Research
Classification of Diabetes Mellitus
The classification of diabetes mellitus is based on its origin and clinical characteristics. The main types of diabetes mellitus are:
- Type 1 diabetes (T1D) 2
- Type 2 diabetes (T2D) 2, 3
- Gestational diabetes mellitus (GDM) 2
- Other forms of diabetes, including maturity onset diabetes of the young (MODY), latent autoimmune diabetes in adults (LADA), ketosis-prone diabetes, and secondary forms of diabetes such as pancreatic cancer and haemochromatosis 4, 5, 6
Subtypes of Diabetes Mellitus
Some studies also recognize subtypes of diabetes mellitus, including:
- Latent autoimmune diabetes in adults (LADA), which accounts for 2%-12% of all cases of diabetes and is characterized by the presence of circulating beta (β) cell autoantibodies 5
- Maturity onset diabetes of the young (MODY), which is a monogenic form of diabetes that typically occurs in young adults 4, 6
- Ketosis-prone diabetes, which is a form of diabetes that is characterized by the presence of ketosis and is often associated with obesity and insulin resistance 4
Diagnosis and Treatment of Diabetes Mellitus
The diagnosis and treatment of diabetes mellitus depend on the type and severity of the disease. For example:
- Type 2 diabetes is typically diagnosed based on fasting plasma glucose, hemoglobin A1C, or oral glucose tolerance testing, and is often treated with lifestyle modifications, metformin, and other medications 3
- Gestational diabetes mellitus is typically diagnosed during pregnancy and is often treated with lifestyle modifications and insulin therapy 2
- LADA is often misdiagnosed as type 2 diabetes, but requires early treatment with insulin and immunomodulatory therapies 5