Side Effect: Low Thyroid Levels (Hypothyroidism)

What is Low Thyroid Levels (Hypothyroidism)?

Having low thyroid levels in your blood is known as hypothyroidism. It is a medical condition that occurs when the thyroid gland does not produce enough thyroid hormone, leading to a range of symptoms related to slowed metabolism. Hypothyroidism can be caused by several factors, including autoimmune disease, radiation therapy, surgical removal of the thyroid gland, and certain medications.

What does Low Thyroid Levels (Hypothyroidism) look like?

The signs and symptoms of hypothyroidism can vary widely from person to person and can be subtle at first. However, common signs and symptoms include:

• Fatigue
• Weakness
• Weight gain or difficulty losing weight
• Cold intolerance
• Joint pain
• Muscle stiffness or weakness
• Constipation
• Dry skin
• Hair loss or thinning
• Depression or mood changes

Who gets Low Thyroid Levels (Hypothyroidism)?

Patients with thyroid cancer will have low thyroid levels after thyroidectomy (removal of the thyroid) and radioactive iodine therapy. Radiation therapy to the head and neck area is also a common cause of hypothyroidism. Thyroid function can be affected by medications used to treat non-thyroid cancers as well, especially if a drug is used that affects the immune system. Examples include:

• Tyrosine kinase inhibitors such as sunitinib (Sutent®), sorafenib (Nexavar®), imatinib (Gleevec®), nilotinib (Tasigna®)
• Interferon-alpha
• Immune checkpoint inhibitors such as Ipilimumab (Yervoy ®), bevacizumab (Avastin®, Zirabev®, Mvasi®)
• Lenalidomide (Revlimid®)
• Bexarotene (Targretin®)
• Alemtuzumab (Campath®, Lemtrada®)

How to prevent Low Thyroid Levels (Hypothyroidism)

Decreasing the risk of hypothyroidism involves careful monitoring of thyroid function during treatment. In some cases, typically before undergoing radiation therapy, a medication (potassium iodide, Lugol’s solution) may be administered before treatment to help protect the thyroid.

How to treat Low Thyroid Levels (Hypothyroidism)

Treatment for hypothyroidism involves hormone replacement therapy with synthetic thyroid hormone, levothyroxine (Synthroid®). The dose of thyroid hormone may need to be adjusted based on individual needs, and regular monitoring of thyroid function is typically required.