The thyroid is a clever little butterfly-shaped gland that lies at the base of your windpipe, above the ‘notch’ at the top of your chest bone. By sending out its messengers’ thyroxine (T4) and triiodothyronine (T3), it controls your metabolic rate. This includes heart rate, weight, appetite, intestinal motility, the amount of glucose you make from your liver and how much insulin your body requires.
As you can imagine, if the thyroid is over- or under-functioning, this will affect your diabetes. Moreover, people with type 2 diabetes are more likely to have thyroid issues, likely from a genetic basis. There are some risk factors associated with developing thyroid disease in people with type 2 diabetes. These include female gender, central obesity (carrying excess weight around your abdomen), diabetic kidney disease, elevated A1C and duration of diabetes. People with type 1 diabetes are also more likely to have an autoimmune thyroid disease such as Graves’ disease or Hashimoto’s thyroiditis.
The occurrence of thyroid disease in people with type 2 diabetes is about 14%, with women having a higher rate than men. Autoimmune thyroid disease occurs in about 10% of people with type 1 diabetes, with the occurrence coming before or after diagnosis. Women with type 1 diabetes are especially vulnerable to developing autoimmune thyroid disease, with the incidence as high as 44% among women of childbearing age and 25% in the first months postpartum.
What are the symptoms?
If the thyroid is overactive (hyperthyroidism), symptoms may include weight loss, hair loss, fast pulse, diarrhea, high blood sugars, sweating and anxiety. If the cause is autoimmune, such as Graves’ disease, the eyes can protrude, giving a look of constant surprise. If the thyroid is underactive (hypothyroidism) symptoms include weight gain, slow pulse, constipation, dry skin, variable blood sugars and fatigue.
With either over- or under-active thyroid function, a person can develop an enlarged thyroid.
How can you test for thyroid disease?
This can be done with a simple and very accurate blood test (it does not require fasting before the test). To regulate the thyroid, the brain constantly checks the level of thyroid hormone in the blood. If it senses that it is too low, it will try to stimulate the thyroid gland. The way it does this is to send out thyroid stimulating hormone (TSH). If your thyroid is underactive, your TSH will be high. The opposite occurs if your thyroid is overactive: the TSH shuts off and is low. This is a very precise test and can pick up small changes even before there are much in the way of symptoms. For people in whom autoimmune disease is suspected, there are also tests that look for antibodies to the thyroid. If antibodies are detected and the TSH is still normal, this individual is at higher risk of developing thyroid disease in the future.
When should you get tested for thyroid disease?
The Diabetes Canada guidelines do not recommend a specific frequency for people with type 2 diabetes to have a TSH screening. If you have symptoms listed above, you can see your healthcare team for a blood test to look for thyroid disease. Often TSH is ordered to check for thyroid disease, as it is one of the more common co-existing conditions in diabetes. The rate of thyroid disease increases with age, especially in postmenopausal women with type 2 diabetes, so if there is any suspicion the TSH could be checked.
For people with type 1 diabetes, because of the frequent occurrence, current guidelines recommend that all children be screened at diagnosis with a TSH and thyroid antibodies test, and then every 2 years. All women with diabetes who are pregnant should have a TSH level done, and those with type 1 diabetes should be screened for thyroid disease at 3 months post-delivery.
Any time blood sugars seem very hard to control for no obvious reason, it may be a reason to check thyroid function.
How is thyroid disease treated?
For an underactive thyroid, the treatment is to replace the thyroid hormone. This means taking a thyroxine pill daily as replacement. If a person has an overactive thyroid, there are medications to decrease the function of the thyroid. Over time, sometimes the inflammation or autoimmune process may burn itself out and the thyroid will become low functioning. In some cases, however, usually with Graves’ disease, the thyroid may continue to be overactive and may need radiation treatment to knock out the function. After this, the individual will need thyroid hormone replacement therapy.
How to take your thyroid medication
Thyroid medication is one of the most commonly prescribed medications in Canada. It works well to replace your own thyroid hormone but may need to be adjusted over time. Once someone is on medication, the dose is adjusted by measuring the TSH. The amount needed is largely based on weight. The higher a person’s weight, the more hormone is needed. The most common reason the TSH changes and practitioners therefore need to change the dose, is that the thyroid medication is forgotten or taken with food that interferes with its absorption.
Thyroid medication must be taken alone with no food and with no other medications, so I often recommend that it be taken at night on an empty stomach and not with certain foods, especially milk. This can be a challenge for people with diabetes. So, be sure to talk to your healthcare team about how and when to take your thyroid medication for the most consistent absorption.
Both diabetes and thyroid disease are common. Luckily, thyroid disease can be treated easily with oral medication. However, balancing blood sugars is not simple at the best of times, so be sure to let your healthcare team know if you are having any symptoms of thyroid disease and get tested.