One of the most common conditions we dispense medications for is for hypothyroidism. We get questions all the time about types of thyroid medications, different combinations and interpreting lab values.
So what is a thyroid anyway? The butterfly shaped thyroid gland is an endocrine gland located below your Adam’s apple and it is responsible for the production and release of thyroid hormones. Thyroid hormones are amino acids that contain iodine. They are crucial for the proper functioning of almost every organ of our system, including (but not limited to) the respiratory, heart and nervous systems. They are also essential for the normal development of children. The two biologically active thyroid hormones in our bodies are T4 (thyroxine) and T3 (triiodothyronine). T4 is converted in our bodies to T3, the more potent, biologically active thyroid hormone. The body synthesizes more T4 than T3 in a ratio of about 14:1, however, T3 is equal to about four times the hormone strength of T4.
The synthesis of thyroid hormones by the thyroid gland is controlled by an endocrine feedback loop. Simply put, control centres in our brain are notified of low levels of T3 and T4 (i.e. at times when more is consumed, for instance due to lack of sleep, stress, etc.), and the production and release of thyroid stimulating hormone (TSH) by the pituitary gland is triggered. TSH “tells” the thyroid gland, through a chemical message, to make more T3 and T4.
This article is focused on hypothyroidism, which happens when our thyroid glands don’t make enough thyroid hormone. It is characterized by an abnormally high TSH level and can be further diagnosed by T4 and T3 blood level tests. Symptoms of hypothyroidism can manifest slowly and can be nonspecific. They can include tiredness, weakness, feeling cold, difficulty concentrating and remembering, weight gain and poor appetite. If left untreated, it can cause increased cholesterol levels and worsening fatigue. The body requires certain building blocks to synthesize thyroid hormones, namely, iodine, selenium, zinc and tyrosine. Iodine deficiency is the leading cause of hypothyroidism in less developed countries. However, in Canada, where iodine is added to salt and other foods, the leading cause of hypothyroidism is Hashimoto’s thyroiditis. It is an autoimmune disease in which the body’s immune system attacks the thyroid tissue, resulting in an inability of the thyroid gland to make thyroid hormone.
The mainstay of treatment of hypothyroidism is thyroid hormone replacement therapy. The first line of treatment is levothyroxine, which is commercially available as a synthetic mimic of the thyroxine (T4) hormone in our bodies. Levothyroxine is converted to T3 in our bodies. It’s usually taken once daily and it’s important to take it on an empty stomach to optimize absorption That being said, if you’re someone who has been taking levothyroxine for years and you haven’t been taking it on an empty stomach, keep doing what you’re doing – changing now can impact your blood levels of the hormone.
Many drugs (both over the counter and prescription) can reduce the absorption of levothyroxine, including certain antacids and supplements. It is ideal to take your thyroid medication at least four hours apart from calcium, iron and magnesium supplements. Some drugs can even impact the conversion of T4 to T3. Your pharmacist can help you figure out whether your medication is being optimally absorbed.
Sometimes, hypothyroidism is treated with synthetic T3, called liothyronine. Treating it just with T3 is a bit more complicated; it involves multiple daily doses due to its short shelf-life and requires high doses that can sometimes result in hyperthyroidism or too much thyroid hormone. Some patients prefer taking desiccated thyroid extract, which is natural in that it is sourced from the thyroid glands of pigs. Desiccated thyroid contains both T3 and T4, and the ratio may vary as it is naturally sourced. Finally, compounded T3 and T4 (or a combination of both) is an option for those wanting a specific ratio or who are allergic to fillers or dyes in the commercially available products.
There are a number of natural supplements available that are marketed to support healthy thyroid function. These include sea kelp (a source of natural iodine), various thyroid complexes and ashwagandha. While more studies need to be done on such products to assess their safety for those with diagnosed hypothyroidism, there is some anecdotal evidence that those with nonspecific symptoms of hypothyroidism may benefit from using them. However, anyone taking other supplements or prescription medications, or those with other medical conditions, should consult their pharmacist before considering taking these supplements.
Sources: Canadian Pharmacists’ Letter: “Levothyroxine Absorption: The Effect of Food and Drugs” US Pharmacist: “Current Challenges in the Management of Hypothyroidism” Pharmacy Practice: “Update on Nonmalignant Thyroid Disorders”
Zenah Surani is the owner and pharmacist of the Glebe Apothecary.