Thyroid disease and diabetes: how the two conditions are linked

People with diabetes sometimes hear that they should also have their thyroid checked. Is there really a link? Health agencies do list diabetes among conditions connected with thyroid disease, and the link is strongest where autoimmune conditions are involved. This article explains what the NIDDK says. It does not mean that one condition causes the other, and it cannot predict your own risk.

Two glands, two kinds of hormones

Insulin, which is made in the pancreas, helps move glucose from the blood into cells. Thyroid hormones, made in the thyroid, control how the body uses energy, according to MedlinePlus. Both are hormone systems, and both can be affected by the immune system turning on the body's own tissues, which is called autoimmunity.

What the sources say about the link

• Type 1 diabetes is autoimmune. The NIDDK's Graves' disease page lists type 1 diabetes among autoimmune conditions.
• Hashimoto's disease is autoimmune. The NIDDK says other autoimmune conditions, including type 1 diabetes, raise the risk of Hashimoto's disease.
• Graves' disease is autoimmune. The NIDDK lists type 1 diabetes among the other autoimmune conditions that raise the risk of Graves' disease.
• Hypothyroidism. The NIDDK includes diabetes among the conditions linked with an underactive thyroid, alongside celiac disease, Sjögren's syndrome, pernicious anaemia, rheumatoid arthritis and lupus.
• Hyperthyroidism. The NIDDK says risk is higher with pernicious anaemia, type 1 or type 2 diabetes, or primary adrenal insufficiency.

None of this means everyone with diabetes will develop a thyroid problem. It means the two can occur together and are worth knowing about.

Symptoms can overlap

Several symptoms are shared by thyroid and diabetes. Tiredness, weight changes and mood changes can occur in both. The NIDDK warns that fatigue and weight gain are common and do not necessarily point to the thyroid. This is why only blood tests can show what is going on, whichever condition you suspect.

Tests

• For thyroid problems, MedlinePlus says TSH is usually the first test a provider orders, and T4, T3 and thyroid antibody tests may follow.
• For diabetes, the NIDDK lists the A1C, fasting plasma glucose, random plasma glucose and oral glucose tolerance tests.

Ask your doctor whether and when thyroid tests are right for you if you have diabetes. They will decide based on your symptoms and history.

Managing both conditions

The treatments are separate. The NIDDK describes thyroid hormone replacement for an underactive thyroid, and medicines, radioiodine or surgery for an overactive one. Diabetes care involves the steps described in our other articles, such as meal planning, activity, monitoring and medicines. Tell every doctor you see about all your conditions and medicines. Do not stop or change prescribed treatment without talking to your doctor.

Things that can complicate care

• The NIDDK says that for people with Graves' disease, seaweed and iodine supplements may worsen hyperthyroidism.
• Too much thyroid hormone medicine can cause an irregular heartbeat or thinning bones, so never adjust it yourself.
• The NIDDK says low blood glucose can be a risk with some diabetes medicines, so tell your team about any new medicines you are prescribed.

When to see a doctor

If you have diabetes and notice unexplained weight change, a fast or slow heartbeat, a swelling at the front of the neck, feeling very hot or very cold, or tiredness that does not improve, ask your doctor about testing. If you have a thyroid condition and notice thirst, passing urine often or blurred vision, ask about a blood sugar test.

Seek emergency help for chest pain, trouble breathing, confusion, fainting, or fruity-smelling breath. In an emergency, call your local emergency number (112 in India, 911 in the United States).

This article is for education only and does not replace advice from your own doctor.