What is type 1 diabetes?
Type 1 diabetes is a chronic autoimmune disease that can develop at any age. There is nothing anyone can do to prevent T1D, and right now there is no known cure.
Read on to find out more about type 1 diabetes (also known as T1D, juvenile diabetes, type 1 diabetes mellitus or insulin-dependent diabetes), including how it’s diagnosed and how it’s different from other types of diabetes.
Type 1 diabetes definition
When someone develops type 1 diabetes, the immune system mistakenly attacks the body’s own cells instead of defending against foreign invaders. In this case, the immune system attacks the beta cells in the pancreas, which produce insulin. Insulin is a hormone that converts glucose from food into energy for the body. Without enough insulin, glucose accumulates in the bloodstream, leading to diabetic ketoacidosis (DKA), a dangerous condition.
Type 1 diabetes is a lifelong condition, and there can be a risk of complications if blood glucose levels (BGLs) are not kept within the optimal range using various management strategies. Some of these deep and long-lasting impacts include:
- kidney damage
- eye damage
- nerve damage to feet
- gum and tooth disease
- sexual dysfunction in both men and women
- damage to the nerves that control internal organ functions such as digestion, bowel function, blood pressure, and heart rate.
Because their bodies can’t produce their own insulin, people with type 1 diabetes have to take insulin every day to make sure their body gets enough of it. They can do this through daily injections or by using an insulin pump. By managing their blood glucose levels, people living with type 1 diabetes can stay healthy and reduce the risk of complications.
It’s a challenging condition, but with treatment and management, people living with type 1 diabetes can live full and happy lives. Read stories from some of our community members who are living and thriving with type 1 diabetes.
Is type 1 diabetes an autoimmune disease?
When our body detects a microbial infection, it responds by causing inflammation. This helps our immune system fight the infection, and eventually that inflammation will go down once the infection has been resolved. However, if our immune system mistakenly attacks healthy cells or tissues, it can be the cause of inflammation and lead to autoimmunity.
In type 1 diabetes, the immune system will mistakenly attack the beta cells in the pancreas. The antibodies that target the beta cells are called anti-islet autoantibodies, and can be detected in blood tests before any symptoms of diabetes start to appear. The presence of these autoantibodies is often used as a way to predict whether someone is at risk of developing type 1 diabetes in the future.
As people living with type 1 diabetes already have an autoimmune condition attacking their beta cells, their immune system is more likely to attack other cells or tissues. That means they’re more likely to also have conditions like coeliac disease and thyroid disease. In fact, it’s estimated that more than 90% of people with type 1 diabetes and another autoimmune disease also have autoimmune thyroid disease.
How common is type 1 diabetes?
Approximately 8.7 million people around the world live with type 1 diabetes. More than 130,000 of those people live in Australia, and eight more Australians are diagnosed each day.
People under the age of 30 are most commonly diagnosed with type 1 diabetes, but it can actually develop at any age. In fact, around half of all diagnoses in Australia are adults.
Taking a closer look at the prevalence of type 1 diabetes in Australia, the National (insulin-treated) Diabetes Register (NDR) found:
- a similar amount of males and females are living with type 1 diabetes
- Indigenous children and young adults have a 20% lower likelihood of living with type 1 diabetes when compared to their non-Indigenous peers
- the occurrence of type 1 diabetes in children and young adults varies depending on their socioeconomic status; the rates were found to be 1.2 times higher among those living in the most disadvantaged areas compared to the least disadvantaged areas.
How is type 1 diabetes diagnosed?
Many people with T1D start their type 1 diabetes diagnosis journey when they visit their GP after noticing something isn’t quite right. They may be experiencing some of the common symptoms of type 1 diabetes, including excessive thirst, frequent urination, tiredness and weight loss. People who have had their type 1 diabetes go unnoticed and untreated for longer could be experiencing a serious condition called diabetic ketoacidosis (DKA), which requires urgent treatment.
GPs and other healthcare providers can carry out several tests for a type 1 diabetes diagnosis. The first check is often a random blood glucose test, done via a finger prick.
Other tests to diagnose type 1 diabetes include the options below.
Random blood glucose test
Fasting blood glucose test
This is a blood test typically conducted in the morning after fasting overnight. The fasting helps give doctors a clear look at how the body manages blood glucose levels without the impact of food intake.
For this test, any result above 7.0 mmol/L indicates diabetes.
Oral glucose tolerance test
After fasting and an initial blood test, people drink a sugary drink then have their blood glucose tested over the course of approximately two hours. This shows the benchmark glucose level without outside influences and later measures how the body responds to carbohydrate (sugar) intake.
After two hours, if the resulting blood glucose level is 7.8 mmol/L or lower, the person is considered to not have type 1 diabetes. A result between 7.8 and 11 mmol/L can indicate prediabetes. If it’s 11.1 mmol/L or higher, it’s likely that the person has diabetes.
Glycated haemoglobin (HbA1c) test
This test measures how much C-peptide is in a person’s blood. C-peptide is a substance that’s made when insulin is produced in the body. When insulin is produced, it is initially created in a form known as proinsulin, which consists of two parts: insulin and C-peptide. The C-peptide is released in a similar pattern as insulin into the bloodstream.
By measuring the levels of C-peptide in someone’s blood, we can get an idea of how much insulin their body is making. Low levels of C-peptide and insulin can suggest a deficiency in insulin production, which is often seen in people with type 1 diabetes.
By measuring C-peptide levels, doctors can also tell the difference between type 1 and type 2 diabetes.
Autoantibody tests look for autoantibodies in the blood, and they can detect these autoantibodies even before type 1 diabetes symptoms appear. By screening for autoantibodies, we can identify people who are at risk of developing T1D and intervene early to try to prevent or delay the onset of the disease.
Autoantibody tests can also help distinguish between type 1 and type 2 diabetes. Unlike other T1D diagnosis tests, autoantibody tests can identify people who have latent autoimmune diabetes in adults (LADA), which is sometimes misdiagnosed as type 2 diabetes.
Patients will often have many autoantibodies tested and measured to confirm a diagnosis of T1D.
Insulinoma-associated-2 autoantibodies (IA-2A)
This test looks for antibodies mounted against a specific enzyme in beta cells. Both the IA-2A and GADA tests (see below) are common T1D autoantibody tests.
The IA-2A test can:
- help distinguish between type 1 and type 2 diabetes
- identify people who are at risk of developing type 1 diabetes, including those who have family members with the condition
- predict whether someone with adult-onset diabetes will need insulin treatment in the future.
Glutamic acid decarboxylase autoantibodies (GADA or anti-GAD)
This test looks for antibodies built against glutamic acid decarboxylase, a specific enzyme in the insulin-producing pancreatic beta cells. GAD antibodies are present in about 75% of people with type 1 diabetes at diagnosis.
The GADA test can be helpful in determining which type of diabetes someone has. It can be used to check whether gestational diabetes might be type 1 diabetes, and also measures the progression of type 1 diabetes, and assesses the risk of developing type 1 diabetes or LADA.
Zinc transporter 8 (ZnT8Ab)
This test investigates autoantibodies targeting an enzyme specific to beta cells. ZnT8A are some of the newest and least understood islet autoantibodies.
They can indicate the same things as the IA-2A test, but can also predict the future development of diabetes in women experiencing gestational diabetes.
Islet cell cytoplasmic autoantibodies (ICA)
This test identifies a type of islet cell antibodies that are present in up to 80% of people with type 1 diabetes. While these autoantibodies are very specific to a type 1 diagnosis, the test lacks sensitivity and is rarely used by clinical labs during diagnosis.
What other types of diabetes are there?
There are about 422 million people living with diabetes internationally. Type 1 diabetes accounts for around 10% of all cases, with the remaining 90% living with type 2 diabetes, LADA or gestational diabetes.
Type 2 diabetes
People with type 2 diabetes develop insulin resistance, meaning their body doesn’t use insulin as well as it should. In later stages of type 2 diabetes, people may also not produce enough insulin.
Type 2 diabetes is caused by a combination of genetics and lifestyle factors, such as being overweight or having a sedentary lifestyle. It can often be managed by diet changes, exercise and medication. However, it is a progressive condition, and some people may need to inject insulin in the later stages of the disease.
Some people who were initially diagnosed as having type 2 diabetes actually have latent autoimmune diabetes of adults (LADA). This is sometimes referred to as type 1.5 diabetes.
People with LADA have features of both type 1 and type 2 diabetes in that their immune system attacks the cells of the pancreas that produce insulin, but they may also have insulin resistance. The destruction of the insulin producing cells is much slower in LADA than in type 1 diabetes.
For some people, LADA can be managed with diet, exercise and medication. However, most people with LADA will require insulin therapy within the first year.
Gestational diabetes refers to diabetes that is first detected during pregnancy. Pregnant women produce large amounts of hormones such as oestrogen and progesterone, which can cause the body to become resistant to the effects of insulin.
By the time a woman reaches the end of the third trimester, her insulin requirements have tripled. If the pancreas is unable to match this increased demand, blood glucose levels start to rise. In general, blood glucose returns to normal after pregnancy. However, women diagnosed with this type of diabetes are at significantly higher risk of developing type 2 diabetes later in life.
Type 1 diabetes affects over 130,000 people in Australia alone. Eight more Australians are diagnosed each day.
- A Chronic Anti-Self-Inflammatory Response (Frontiers in Immunology)
- A glutamic acid decarboxylase autoantibodies test (GAD antibodies test) is used to help discover whether someone has either type 1 diabetes or latent autoimmune diabetes of adulthood (LADA) (Diabetes UK)
- Diabetes (World Health Organization)
- Diabetes autoantibody panel (UC San Diego Health)
- Diabetes: Australian facts, type 1 diabetes (Australian Institute of Health and Welfare)
- Diabetes: pathology tests explained (Australasian Association for Clinical Biochemistry and Laboratory Medicine)
- Diabetes type 1 (Better Health Channel)
- EZNT8 – Overview: zinc transporter 8 (ZnT8) antibody, Serum (Mayo Clinic Laboratories)
- Insulin C-Peptide (University of California San Francisco)
- Islet autoantibody testing (American Association for Clinical Chemistry)
- Islet autoantibody testing: an end to the trials and tribulations? (National Library of Medicine)
- Oral glucose tolerance testing (Royal Australian College of General Practitioners)
- Type 1 diabetes (Diabetes Australia)
- Type 1 diabetes and autoimmunity (Clinical Pediatric Endocrinology)
- Type 1 Diabetes Index
- What has zinc transporter 8 autoimmunity taught us about type 1 diabetes? (Diabetologia)
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