Could Your Thyroid Medication Need an Adjustment?

hypothyroid fatigue article

The thyroid gland is small, but it has a big job. It releases two hormones known as T4 (thyroxine) and T3 (triiodothyronine), which are essential to regulating metabolism and other body functions.

There are a number of thyroid-related health conditions, with the most common being hypothyroidism. This occurs when the thyroid gland is underactive, which means that it is not secreting enough of the thyroid hormones. It is possible to have an underactive thyroid and have no symptoms at all, though it is more likely that individuals will feel tired or have a lack of energy. Other symptoms may include dry skin and hair, sensitivity to cold, slow heart rate, muscle weakness, or difficulty concentrating, for example. Since these symptoms can overlap with other health conditions, it is important to see your doctor if you suspect thyroid problems.

Your doctor can request lab tests that will help to verify the diagnosis. Stop any biotin supplements at least two days before lab tests, as biotin can lead to an incorrect diagnosis. Once hypothyroidism is diagnosed, your doctor may prescribe thyroid hormone replacement to keep levels in the normal range, or if you have no symptoms, simply monitor your lab tests over time.

We are often asked if it is helpful to take iodine supplements, since iodine is needed for production of thyroid hormones. In Canada, the salt we purchase at grocery stores is “iodized” salt, so dietary intake provides sufficient iodine. In fact, supplementing iodine or consuming excessive amounts in foods (e.g., kelp) can lead to hyperthyroidism, where the thyroid gland produces too much thyroid hormone.

There are many foods and drugs that interact with thyroid hormone medications. For this reason, it is best to take thyroid hormone on an empty stomach, separate from other medications. We recommend that calcium and iron supplements (or foods that contain significant calcium), as well as coffee or alcohol be taken at least four hours apart from thyroid hormone, if possible. Fibre supplements (e.g., psyllium fibre) can delay absorption and should also be taken separately.

Your doctor will adjust the dose of your thyroid medication based on repeat lab tests, so it is important to take it consistently. If you have been taking it with food (even food that is high in calcium, such as dairy products), continue to take it the same way all the time, as your doctor has already determined the dose based on your regular use. Typically, lab tests are done annually and no dose adjustments are needed. However, for women, the dose may need to be adjusted when there are changes in estrogen levels (estrogen binds to thyroid hormone and reduces its absorption). Estrogen levels rise during pregnancy, so a higher dose is needed, whereas the reverse is true at menopause.

Follow up with your pharmacist and doctor if there is any change to your symptoms, if you experience a significant change in your weight, or if you have been missing doses of your medication, as these will likely necessitate a dose adjustment. As always, we are here to help you manage your medications and achieve your best health.

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