Type 1 diabetes is a medical disorder characterized by the autoimmune destruction of the pancreatic islet cells, eventually leading to the absence of the production of insulin and other important hormones. The lack of insulin results in a decreased ability of glucose to enter the cells, leading to hyperglycemia, or high blood glucoselevels.
Type 1 diabetes is believed to be caused by the combination of a genetic predisposition and an environmental trigger. Formerly known as juvenile diabetes, type 1 diabetes can be diagnosed in childhood, as well as in adulthood. In fact, between 25% and 50% of type 1 diabetes diagnoses today occur in individuals over 18 years old.
The main symptoms of untreated type 1 diabetes include:
- Extreme thirst and hunger
- Frequent urination
- Weight loss
- Changes in vision
- Frequent infections and slow wound healing
Individuals with type 1 diabetes must monitor their blood glucose levels and administer exogenous insulin via injections or an insulin pump to allow for glucose metabolism. Left untreated, the condition is deadly and suboptimal management can result in numerous complications, including micro- and macrovascular problems in numerous organ systems as well as nerve damage. However, with optimal blood glucose control, the likelihood of complications can be minimized.
Stages of Type 1 Diabetes Development
There are several main steps in the typical pattern of developing of type 1 diabetes:
- Islet cell autoimmunity, characterized by the presence of autoantibodies,
- A decrease in beta cell mass that reduces insulin production and results in slightly elevated blood glucose levels, and
- Overt hyperglycemia accompanied by the clinical symptoms of diabetes.
Diagnosing Type 1 Diabetes
A diabetes diagnosis is typically made based on blood glucose levels and the hemoglobin A1c test. In general, two fasting blood glucose levels over 126 mg/dL (~ 7.0 mmol/L), a random reading of over 200 mg/dL (~ 11 mmol/L), and an A1c of 6.5% (~ 47.5 mmol/mol) or greater is characteristic of diabetes. An A1c level between 5.7%-6.4% (~ 38.8 mmol/mol-46.4 mmol/mol) is considered to be characteristic of “pre-diabetes.”
Because early onset of type 1 diabetes may present with no overt clinical symptoms, misdiagnoses of pre-diabetes or type 2 diabetes frequently occur in the adult population. It is estimated that between 5% and 15% of adults who are diagnosed with type 2 diabetes may actually have type 1 diabetes.
The clinical tests to check for diabetes may include serum C-peptide levels as well as antibody testing. Circulating C-peptide levels correspond to the amount of endogenous insulin, while the presence of autoantibodies against islet cells (ICAs), glutamic acid decarboxylase (GADAs), insulin (IAAs), transmembrane tyrosine phosphatase (IA2As), and ZnT8 (ZnT8As) indicate an autoimmune response.
Autoantibodies can be detected years before a diagnosis is made, and greatly increase the risk of developing type 1 diabetes. However, not all patients with type 1 diabetes have autoantibodies, highlighting the heterogeneous and multifactorial nature of the disease. In addition, far from all individuals who are diagnosed with diabetes undergo these clinical tests, which is likely a large contributor to the high misdiagnosis rates.
What Is LADA?
The type 1 diabetes progression timeline can vary greatly from individual to individual. In some people, the process of islet cell destruction appears to occur very rapidly, in as little time as a few weeks or months, whereas in others, the process can progress very slowly, over the course of several years or more.
As a result of this, latent autoimmune diabetes in adults (LADA) is recognized as a subset of type 1 diabetes that is characterized by a slow progression and has also been described as an in-between type of diabetes, exhibiting symptoms of both type 1 and type 2 diabetes. However, in the last decade, many researchers have shied away from making this distinction, as the diagnostic criteria for LADA are vague and the genetic similarities between LADA and more classically-presenting type 1 diabetes are striking.
Because type 1 diabetes is often misdiagnosed in the adult population, it is of utmost importance for patients and providers to understand how the disease progresses. Ensuring that the appropriate initial tests and follow-up monitoring are included in making the correct diabetes diagnosis is crucial to providing the most suitable treatment early on.
Originally published at Diabetes Daily
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