Type 5 diabetes has just been recognised as a distinct form of diabetes by the International Diabetes Federation. Despite the name, there are more than a dozen different types of diabetes. The classification isn't quite as tidy as the numbering suggests.
Author
- Craig Beall
Senior Lecturer in the Neuroscience of Energy Homeostasis, University of Exeter
Here's a clear guide to the different types, including some that you may not have heard of, along with information about what causes them and how they are treated.
Type 1
Type 1 diabetes is caused by the body's immune system mistakenly attacking the insulin-producing cells in the pancreas. This autoimmune reaction can occur at any age, from infancy through to old age.
It is not linked to diet or lifestyle. Instead, it probably results from a combination of genetic predisposition and environmental triggers , such as viral infections.
Treatment involves lifelong insulin therapy, delivered through injections or pumps.
A small number of people who struggle with low blood sugars, called hypoglycaemia, can receive new cells in the pancreas that produce insulin from deceased donors . For many, this reduces the number of insulin injections needed. Some can stop taking their insulin altogether.
What's more, dozens of people have now received stem-cell-derived transplants to effectively "cure" their diabetes , although people still need to take strong immune-suppressing drugs. This treatment is not yet widely available.
Type 2
Type 2 diabetes is the most common form of the condition and is often linked to having a high BMI (body mass index). However, it can also affect people of normal weight, particularly those with a strong genetic predisposition .
Certain ethnic groups, including south Asians and people of African and Caribbean descent, are at higher risk - even at lower body weights.
Boosting the body's production of insulin can help to control blood sugar levels. Some drugs boost insulin production from the pancreas, while others improve insulin sensitivity.
Metformin , for example, is taken by hundreds of millions of people worldwide. This drug improves insulin sensitivity and switches off sugar production by the liver.
There are dozens of different drugs to help control blood sugar in type 2 diabetes. Tailoring treatment to the individual has been shown to improve health outcomes significantly.
Lifestyle changes can also reverse diabetes. This can be done by keeping a low-calorie diet of 800 calories a day. In a research trial maintaining this diet for 12 months reversed diabetes in 46% of people.
Gestational diabetes
This type of diabetes develops during pregnancy , typically between weeks 24 and 28. It is triggered by hormonal changes that reduce the body's sensitivity to insulin.
Risk factors include being overweight or obese, a family history of diabetes, and giving birth to a large baby in a previous pregnancy.
Those from Middle Eastern, south Asian, black and African Caribbean backgrounds are also at higher risk of gestational diabetes. Age is also a factor, as insulin sensitivity declines with age. This can be treated with diet and exercise, tablets or insulin injections.
Rarer forms of diabetes
There are at least nine sub-types of diabetes that include rare genetic forms, sometimes caused by a single genetic change. Others can be caused by treatment, such as surgery or drugs, such as steroids.
Neonatal diabetes appears early in life. Some of the genetic changes affect how insulin is released from the pancreas. Some people still make their own insulin, so can be treated with tablets that help pancreas cells to push out insulin.
Maturity onset diabetes of the young, or Mody, occurs later in life and is linked to genetic changes . There are several gene changes, with some affecting how pancreas cells sense sugar and others affecting how the pancreas develops.
Type 3c diabetes is different. It is caused by damage to the pancreas. People with pancreatic cancer, for example, can develop diabetes after parts of the pancreas are removed. It can also develop after pancreatitis (inflammation of the pancreas).
Those with cystic fibrosis are also at a higher risk of developing diabetes. This is called cystic fibrosis-related diabetes. The risk increases with age and is very common, with around a third of people with cystic fibrosis developing diabetes by the age of 40.
Type 5
This newly designated form is linked to malnutrition during early life. Type 5 diabetes is more common in poorer countries. It affects around 20-25 million people worldwide .
People have low body weight and lack insulin. But the lack of insulin is not caused by the immune system. Instead, the body may not have received the correct nutrition during childhood to help the pancreas develop normally.
Studies with rodents have shown that a low-protein diet during pregnancy or adolescence leads to poor pancreas development. This has been known for many years. Having a smaller pancreas is a risk factor for different forms of diabetes. Essentially, having fewer reserves of insulin-producing cells.
Diabetes is an umbrella term for a range of conditions that result in raised blood sugar levels, but the underlying causes vary widely. Understanding the specific types of diabetes someone has is crucial to providing the right treatment.
As medical science evolves, so does the classification of diabetes. Recognising malnutrition-related diabetes as type 5 will stimulate discussion. This is a step towards better global understanding and care - especially in low-income countries.
Craig Beall currently receives funding from Diabetes UK, Breakthrough T1D, Steve Morgan Foundation Type 1 Diabetes Grand Challenge, Medical Research Council, NC3Rs, Society for Endocrinology and British Society for Neuroendocrinology.
