THYROID CANCER TREATMENT AND THE RISK OF HYPOTHYROIDISM

Treatment for thyroid cancer

Thyroid cancer is the most common endocrine cancer. There are four main types of thyroid cancer: papillary, follicular, medullary and anaplastic. Papillary and follicular cancers (often called 'well-differentiated thyroid cancers') are the most common types, accounting for about 90% of thyroid cancers 1. Sherman SI. Thyroid carcinoma. Lancet 2003; 361(9356): 501-11

In most cases patients are treated with surgical removal of the thyroid, known as a thyroidectomy.

Following thyroidectomy, the body is unable to produce thyroid hormone, which is used to help regulate many functions in the body, such as metabolism and calcium usage. Patients are typically treated with thyroid hormone replacement therapy post-surgery to help the body maintain appropriate levels of thyroid hormone. 

The risk of hypothyroidism

Patients who have had total or near-total thyroid removal surgery may sometimes need treatment with radioactive iodine (radioiodine) during a process known as ablation to destroy any remaining thyroid tissue in the body. In order to ablate, physicians need to stimulate remaining thyroid tissue by withholding thyroid hormone. In many patients, interruption of thyroid hormone replacement therapy can result in a form of a condition known as hypothyroidism, which occurs when the body lacks sufficient levels of thyroid hormone.

In addition to the ablation procedure, patients must be regularly monitored for a return of cancer. During the monitoring procedure, patients may need to stop taking hormone replacement therapy, which can also lead to symptoms of hypothyroidism.

Symptoms of hypothyroidism include 2. Luster et al. Thyroid hormone withdrawal in patients with diffeentiated thyroid carcinoma: a one hundred thirty-patient pilot survey on concequences of hypothyrodism and a pharmacoeconomic comparison to recombinant thyrotropin administration, 2012, doi/pdf/10.1089/thy.2012.0205

Fatigue

Difficulty concentrating

Cold intolerance

Weight gain

Sleep disturbance

Dry skin

Constipation

Slow movements

Effects of hypothyroidism

Severe hypothyroidism can lead to a range of clinical morbidities, including cardiovascular, cerebrovascular, and lipid defects. The condition can also reduce or alter brain activity, cardiac efficiency, and heart rate. Patients may have a diminished mental state when they experience hypothyroidism, and can become depressed, anxious, or lethargic. 3. Duntas LH and Biondi B. Short-term hypothyroidism after levothyroxine-withdrawal in patients with differentiated thyroid cancer: clinical and quality of life consequences. Eur J Endocrinol 2007; 156(1):13-19

A recent study found that severe hypothyroidism can affect cognitive and motor skills and can limit the ability to perform complex activities requiring rapid responses such as driving. 4. Smith et al. Reversible Cognitive, Motor, and Driving Impairments in Severe Hypothyroidism. Thyroid; 2015, 25(1):28-36

GZEMEA.ENDO.17.08.0261
August 2017