TYPE 1 DIABETES
In type 1 diabetes (formerly referred to as juvenile onset
diabetes or insulin-dependent diabetes mellitus), a person’s immune system attacks its own beta cells and
destroys them. This is known as autoimmune injury. To control the elevated glucose levels, a person with
this kind of diabetes has to be treated with insulin injections. Most people with this kind of diabetes are
Type 1 diabetes occurs when the immune system that normally
protects the body against infections goes wrong and attacks the beta cells that make insulin. There are
genetic factors and environmental factors that cause the immune system to do this.
Type 1 Diabetes and Genetics
Scientists have identiﬁed a
number of genes that increase an individual’s risk for developing type 1 diabetes. The genes that are
particularly important include the following:
• Several genes located in a
region of the human genome called human leukocyte antigen (HLA). Two of the genes (called DR and DQ) code
for proteins that help the immune system recognize foreign proteins such as those that make up viruses and
bacteria. There are many forms of these two genes, and the ones that increase the individual’s susceptibility to
type 1 diabetes are called DR3.DQ2 and DR4.DQ8.
• The insulin gene. It
has been shown that insulin teaches the immune system not to react against the beta cells—this teaching process
is referred to as inducing tolerance. People with type 1 diabetes are more likely to have a form of the insulin
gene that is less effective in maintaining tolerance.
These genetic factors explain
why the risk of type 1 diabetes is increased if you have a family member with the disease. If you have a family
member with type 1 diabetes, your risk is 5 to 6 percent, compared to the risk in the general population, which
is 0.4 percent. In identical twins this risk increases to 30 to 40 percent. Table 2-1 summarizes the risk if a
family member has type 1 diabetes:
Type 1 Diabetes and the
The environment plays a big role in the development of type 1 diabetes—in fact it’s twice as
important as the genes. The evidence for this comes from several different
• First, for the past forty years, the incidence of type 1 diabetes has been increasing,
and it is occurring in younger children. This time period is too short for this to be a change in the genetic
makeup of the population.
Second, type 1 diabetes is more common in the northern latitudes ( Scandinavia) and becomes less frequent as you
go toward the equator. This is not because people at the equator are genetically protected—when they migrate to
northern latitudes, they too become susceptible to type 1 diabetes. For example, it was recently shown that Pakistani children born
and raised in England have a higher risk for developing type 1 diabetes compared to children who have lived in
Pakistan all their lives.
What is it in the environment that increases the risk of getting type 1 diabetes? We do not
know. However, there have been a number of hypotheses: one hypothesis relates type 1 diabetes to infections with
viruses such as rubella and Coxsackie B4; another hypothesis relates type 1 diabetes to the consumption of cow’s
milk. So far, neither of these has been conﬁrmed as being the culprit.
One reason it is hard to ﬁgure out which environmental factor is important is that the factor
may be important for initiating the autoimmune process, but not for maintaining it. Since the immune attack
starts many years before a person develops diabetes, it is difﬁ cult to figure out what environmental factor
was present right at the beginning when the autoimmune process ﬁrst started. There has been a suggestion that in
the developed countries, a lack of childhood infections means that the immune system does not develop properly,
and this leads to autoimmunity and the development of conditions such as asthma and diabetes. This theory is
known as the hygiene hypothesis.
Other Autoimmune Diseases in People with Type 1 Diabetes
The genetic and environmental factors that increase the risk for type 1 diabetes also increase
the risk for other autoimmune diseases. Up to 20 percent of people with type 1 diabetes also have autoimmune
thyroid disease, especially underactive thyroid disease (Hashimoto’s thyroiditis). Once in while, we also see
thyroid over activity
(Graves’ disease) accompanying type 1 diabetes. Another disease that occurs more
frequently in people with type 1 diabetes is celiac disease. In this disease, a person is very sensitive to
gluten in wheat. About 5 percent of children diagnosed with type 1 diabetes have gluten sensitivity. Addison’s
disease, a rare condition in which there is autoimmune failure of the adrenal glands, also occurs with slightly
increased frequency in people with type 1 diabetes
HOW IS TYPE 1
Type 1 diabetes is treated using insulin injections. Oral medicines that are used to treat
type 2 diabetes do not work in people with type 1 diabetes because they depend on having the pancreas still
making signiﬁcant amounts of insulin. Early in the disease, a person with type 1 diabetes still has the ability
to make and release insulin, and so you will require only a small amount of insulin to keep glucose under
control. This early period is referred to at the as the honeymoon phase and can last from a few months to
several years. Eventually, however, most of the beta cells are lost, and you will be totally dependent on
insulin injections for your insulin needs.
Type 1 diabetes can occur at
any age and in any ethnicity, but is more common in children and young adults of Caucasian ancestry. Most cases
occur in families where there is no history of type 1 diabetes, but when you have a family member with type 1
diabetes, your risk of getting the disease is higher.