Clinical Thyroidology® for the Public

Summaries for the Public from recent articles in Clinical Thyroidology
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THYROID CANCER
Is there a risk of heart disease in thyroid cancer patients?

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BACKGROUND
Thyroid cancer is the most common endocrine cancer in the world. Overall, thyroid cancer has an excellent prognosis. Given the low risk of death caused directly by thyroid cancer, it is important to understand what other factors contribute to illness and death among patients with thyroid cancer. It remains controversial whether patients with thyroid cancer have an increased risk of heart disease as compared to the general population. Some studies suggest that some risk factors for heart disease, such as obesity and high cholesterol levels, are also associated with an increased risk of developing thyroid cancer. Similarly, some studies suggest that patients with thyroid cancer may be at an increased risk of developing high blood pressure and diabetes, two conditions that can increase one’s risk for developing heart disease. Finally, a low TSH level on thyroid hormone treatment, which may be part of the treatment of thyroid cancer, has been associated with an increased risk of atrial fibrillation.

The goal of this study was to determine the risk of death due to heart disease in a population of adult patients with thyroid cancer compared to a population of patients without thyroid cancer.

THE FULL ARTICLE TITLE
 Qiang JK et al 2022 Risk of adverse cardiovascular outcomes in differentiated thyroid cancer survivors: A systematic review and meta-analysis. Thyroid. Epub 2022 Oct 20. PMID: 36074932.

SUMMARY OF THE STUDY
The authors identified 7 studies to include in their analysis. In one study that examined 2096 Dutch patients (524 with thyroid cancer and 1572 without thyroid cancer), the risk of death from heart disease was more than 3 times greater among patients with thyroid cancer. Furthermore, among patients with thyroid cancer, a lower TSH level was associated with a higher risk of death from heart disease.

In an analysis of 4428 patients with thyroid cancer, combined from three separate studies, the authors found that the risk of atrial fibrillation is greater among patients with thyroid cancer compared to the general population. In additional analyses, the authors determined that the risk of developing heart disease, heart failure, and stroke among patients with thyroid cancer is not significantly different from that of the general population.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
The study findings suggest that patients with thyroid cancer may be at an increased risk of developing atrial fibrillation and of death from heart disease as compared to the general population. While this data is interesting, more population-based studies are needed to understand the relationship between thyroid cancer and heart disease.

— Debbie Chen, MD

ABBREVIATIONS & DEFINITIONS

Papillary thyroid cancer: the most common type of thyroid cancer. There are 4 variants of papillary thyroid cancer: classic, follicular, tall-cell and noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP).

Levothyroxine (T4): the major hormone produced by the thyroid gland and available in pill form as Synthroid™, Levoxyl™, Tyrosint™ and generic preparations.

Thyroid hormone therapy: patients with hypothyroidism are most often treated with Levothyroxine in order to return their thyroid hormone levels to normal. Replacement therapy means the goal is a TSH in the normal range and is the usual therapy. Suppressive therapy means that the goal is a TSH below the normal range and is used in thyroid cancer patients to prevent growth of any remaining cancer cells.

TSH: thyroid stimulating hormone — produced by the pituitary gland that regulates thyroid function; also the best screening test to determine if the thyroid is functioning normally.

Atrial fibrillation: an irregular and often very rapid heart rhythm (arrhythmia) that can lead to blood clots in the heart. Atrial fibrillation increases the risk of stroke, heart failure and other heart-related complications.

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