Clinical Thyroidology® for the Public

Summaries for the Public from recent articles in Clinical Thyroidology
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Are “bad habits” good for thyroid cancer? Smoking, alcohol and thyroid cancer risk

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We do not know the exact causes of thyroid cancer. Researchers have been trying to find out factors that may be associated with thyroid cancer for several years. Smoking and alcohol consumption may cause many cancers. Interestingly, past studies showed either no relation or even decreased risk associated with these factors.

The aim of this study was to find out whether there was an association between cigarette smoking and alcohol consumption and thyroid cancer risk.

Yeo Y et al 2022 Smoking, alcohol consumption, and the risk of thyroid cancer: A population-based Korean cohort study of 10 million people. Thyroid 32:440–448. PMID: 35236095.

The study was done in Korea using Korean National Health Insurance (KNHI) database which had information on over 9 million individuals over an average of 8 years. In this very large group of people, 89,527 had thyroid cancer diagnosis. The available data included smoking status, use of alcohol, regular exercise, diabetes mellitus, high cholesterol, and income. The specific type of cancer was not available.

Smoking status was divided into: never, past or present. The duration of smoking was divided into categories of less than 10 years, 10 to 20 years, and more than 20 years. Alcohol use was classified as never, mild if less than 15 g/ day, moderate if 15-30 g/day, or heavy if more than 30g/ day. (15 grams of alcohol is approximately 5 oz of wine or 12 oz of beer, or 1.5 oz of hard liquor.)

Current smokers had a 36% lower risk of thyroid cancer compared to nonsmokers; risk was lower especially if they were also less than 65 years old. Past smokers and never smokers had a similar risk. The amount or duration of smoking did not affect the risk. Alcohol use was also associated with a lower risk of thyroid cancer. More frequent and heavier consumption had lower risk.

Surprisingly, the researchers in this study observed a lower risk of thyroid cancer in individuals with increased alcohol consumption and smoking. The reasons for this are unclear. Certainly, this does not mean your doctor will start recommending smoking or drinking alcohol regularly to prevent thyroid cancer since this would cause more harm than good. However, the findings of this very large study are important and intriguing. Further investigations to better understand how these factors could offer protection from thyroid cancer may help develop new prevention strategies.

— Ebru Sulanc, MD


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).

September is Thyroid Cancer Awareness Month