When you have thyroid cancer, a key starting point for treatment is almost always surgery, known as thyroidectomy, to remove all or part of your thyroid gland. A full or total thyroidectomy — removing the entire gland — is the most common first step in your thyroid cancer treatment.
Thyroid hormone is essential for all of your body’s functions. When your thyroid has been entirely removed — or enough of it has been removed that it impairs the gland’s ability to produce hormone — you become hypothyroid and need to replace that missing hormone. That is accomplished by taking a prescription thyroid hormone medication.
The most commonly prescribed thyroid hormone replacement medication is a synthetic form of the thyroid hormone thyroxine (T4), known as levothyroxine. Some of the brand names you might recognize include Synthroid, Levoxyl, and Tirosint. Levothyroxine is the thyroid drug preferred by most endocrinologists and physicians for thyroid hormone replacement after thyroid cancer.
Your thyroid produces another key hormone — triiodothyronine (T3) — that may also be in low supply after thyroid surgery. In some cases, physicians will prescribe a synthetic version of this hormone, liothyronine, in addition to your levothyroxine. Liothyronine is available as a generic, and the only brand name in the United States is Cytomel. In some cases, your physician may also prescribe a custom-compounded form of sustained-release liothyronine, available by prescription only from compounding pharmacies. T4/T3 combination therapy is much less common than levothyroxine (T4)-only treatment after thyroid cancer.
Even less common is the use of another type of thyroid hormone replacement drug called natural desiccated thyroid or NDT. The key brands of NDT include Armour Thyroid and Nature-throid. NDT is made from the dried thyroid glands of pigs, and includes natural forms of both T4 and T3. NDT is most often prescribed by integrative and holistic and integrative health care providers.
Starting your thyroid hormone medication
When you start your thyroid-hormone medication depends on your treatment program. In some cases, after surgery, you will also be scheduled for radioactive iodine (RAI) treatment to ablate any remaining remnants of thyroid tissue. You will typically not receive thyroid hormone medication until you have undergone RAI and your doctor is confident that you are cancer-free. At that point, a dosage of thyroid hormone medication will be prescribed, usually based on your body weight.
Your practitioner should recheck your thyroid levels frequently until you reach an optimal and stable dosage.
Once your thyroid levels have stabilized at your physician’s target TSH levels, your doctor will likely recommend periodic checks every six months or yearly at most.
Target levels and suppressive therapy
An important note: If you are at a higher risk of recurrence of your thyroid cancer, your doctor may recommend what’s known as “suppressive therapy.” This means that the goal of your thyroid hormone replacement will be to keep your thyroid stimulating hormone (TSH) level very low, or even undetectable. Having a suppressed TSH level can help prevent regrowth or recurrence of thyroid cancer.
If you have a lower-risk thyroid cancer, your practitioner may recommend that your thyroid hormone replacement dosage should maintain your TSH level within the normal reference range. The typical TSH reference range at most labs in the United States is around 0.5 mIU/L to 5.0 mIU/L. Note, however, that many thyroid patients report that they feel best when their TSH level is below 2.5 mIU/L.
Be sure to discuss your targeted TSH level and whether you need suppressive therapy with your health care provider so that you are receiving the best follow-up care after your thyroid cancer diagnosis.
Thyroid hormone replacement withdrawal
For some thyroid cancer survivors, periodic nuclear scans will be scheduled to detect any recurrence. Prior to those scans, your practitioner will have you stop taking your thyroid hormone replacement medication — and usually follow a low-iodine diet — so that the scan can be as accurate as possible. An accurate scan requires an elevated TSH level and an absence of iodine in your system.
In the past, patients who had to go off their thyroid medication for several weeks experienced significant hypothyroidism symptoms, including fatigue, weight gain, depression, brain fog, and concentration problems. Thankfully, there is now an alternative. A drug called thyrotropin alfa for injection (brand name Thyrogen) can be given after you stop your regular thyroid hormone medication. This drug relieves your hypothyroidism symptoms while allowing for an accurate scan.
If a scan detects any recurrence, you may be scheduled for further treatment, such as additional surgery or RAI. After the scanning and treatment process is complete, your doctor will advise you on when to restart your regular thyroid hormone replacement medication.
Some tips on taking your thyroid hormone medication:
Calcium can interfere with absorption of thyroid medication, so avoid foods and supplements that are high in calcium — such as calcium supplements, antacids, milk, and calcium-fortified juice — four hours before or after taking your thyroid medication.
Iron can also interfere with absorption of thyroid medication, so avoid taking iron supplements four hours before or after your thyroid medication.
Is your thyroid treatment optimal?
Keep in mind that if you are taking levothyroxine, and your TSH level falls within the reference range (or is suppressed), you may still experience significant hypothyroidism symptoms, including fatigue, weight gain, depression, brain fog, hair loss, and other challenges. Or, if you are on suppressive therapy, you may experience hyperthyroid symptoms, such as anxiety, insomnia, weight loss, diarrhea, and fatigue. If this is your experience, it’s time to explore treatment modifications with your health care provider. Some helpful options to achieve optimal treatment could include:
A change in your dose. Some patients feel better with even a slight adjustment in dosage to raise or lower the TSH level and relieve symptoms.
Switching your brand of levothyroxine. Some patients are, for example, allergic or sensitive to Synthroid because it contains acacia (a derivative of tree bark) and lactose. You may have relief of symptoms after switching to one of the other brands that are free of those fillers. Specifically, the liquid, gel-cap form of levothyroxine, Tirosint, is designed for maximum absorption for people with allergies or problems with digestion and absorption.
A switch to T4/T3 combination therapy. Some patients need supplemental T3 in order to relieve hypothyroidism symptoms. This can be accomplished by adding a T3 drug such as liothyronine (Cytomel), or a compounded, sustained-release T3 to your levothyroxine treatment.
Switching to — or adding — a T4/T3 natural desiccated thyroid drug. Some patients find that an NDT like Nature-throid or Armour can better relieve symptoms.
See more helpful articles:
Causes of Hypothyroidism
Hypothyroidism and the TSH Test