What are anti-glutamic acid decarboxylase antibodies?

Glutamic acid decarboxylase (GAD) is an enzyme involved in the production of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter found in the brain. Neurotransmitters are chemicals that facilitate the transmission of signals between neurons. Inhibitory neurotransmitters decrease the chance that a signal will be passed to the next neuron, where excitatory neurotransmitters increase the chance that a signal will be passed to the next neuron.

Both are essential for correct function of the brain and central nervous system. Antibodies are proteins typically produced by the immune system to target and protect against harmful entities. In some cases, the immune system can malfunction, producing antibodies which target and attack the body’s own cells.

Disorders caused by this process are called autoimmune diseases. Anti-glutamic acid decarboxylase antibodies are autoantibodies that target and destroy GAD, which in turn leads to a reduction in GABA. Conditions associated with anti-GAD antibodies include type-1 diabetes, cerebellar ataxia, stiff person syndrome and autoimmune conditions such as rheumatoid arthritis.

Why take the test?

This test screens for the presence of anti-glutamic acid decarboxylase antibodies. It is typically used to diagnose type-1 diabetes, cerebellar ataxia, stiff person syndrome and autoimmune conditions such as rheumatoid arthritis.