When I hear stories from friends who have visited Korea, there's always something that comes up. They mention that their health check-up package included a thyroid ultrasound, and that a small nodule was found.

However, when they return to the U.S. and ask their primary care physician for the same test, the response is often lukewarm. They are told that if there are no symptoms, there's no need for the test.

At first, I thought it might be due to insurance savings. But upon further investigation, the reasons became quite clear.

The U.S. Preventive Services Task Force (USPSTF) does not recommend thyroid cancer screening for asymptomatic adults. In grading terms, it's a D, meaning they advise against it.

This recommendation was first made in 1996 and was maintained during a review in 2017. This indicates that the conclusion has not changed upon reevaluation.

The committee believes that the harms of screening asymptomatic individuals outweigh the benefits. This applies to both physical examinations and ultrasounds. They also noted that there have been no studies directly comparing health outcomes between screened and unscreened groups.

Wait! The harms mentioned here do not refer to the test itself but to what happens afterward. It involves finding cancers that do not need to be found and the subsequent surgeries that follow.

The country that illustrates this most dramatically is Korea. Since the national cancer screening program began in 1999, thyroid ultrasounds have become widespread in health check-ups.

A paper published in the New England Journal of Medicine (NEJM) in 2014 by Professors Ahn Hyung-sik and Gilbert Welch summarized this phenomenon. In 2011, the thyroid cancer diagnosis rate in Korea was 15 times higher than in 1993.

This certainly looks like an epidemic. However, during the same period, the mortality rate from thyroid cancer remained almost unchanged.

What does it mean that the number of patients increased significantly while the number of deaths stayed the same? It means that most of the newly discovered cancers were small papillary cancers that would not have caused any problems throughout a person's life.

In medicine, this is referred to as overdiagnosis. The cancer is real, but it's a case of finding a cancer that would have gone unnoticed without causing any issues.

The problem is that most patients who receive a diagnosis end up undergoing surgery. The paper reported that 11% of patients who had surgery experienced hypoparathyroidism.

If the parathyroid glands are damaged, it can lead to difficulties in calcium regulation, requiring lifelong medication. If the thyroid is removed, patients must also continue taking thyroid hormone medication.

This burden follows the relief of having detected cancer early. Honestly, this part makes me feel a bit conflicted.

Fortunately, the story doesn't end here. In 2014, the issue of overdiagnosis became widely recognized in Korea, leading to a reduction in asymptomatic ultrasounds and a decrease in both thyroid cancer diagnoses and surgeries.

Doctors raised the issue first, and the country changed its direction. I find this aspect to be quite hopeful.

The American Thyroid Association (ATA) guidelines reflect a similar trend. The 2015 guidelines state that nodules smaller than 1 cm should not undergo biopsy unless there are specific suspicious findings.

For very low-risk micro-papillary cancers, active surveillance without immediate surgery is also recognized as an option. Institutions like Kumamoto Hospital in Japan have been practicing this approach for a long time.

That said, this does not mean that thyroid cancer is insignificant. According to the National Cancer Institute (NCI) SEER data, the 5-year relative survival rate for localized thyroid cancer is over 99%, but it is much lower for cases that have spread.

Wait! There are clear exceptions to these recommendations. If a nodule is palpable or swollen, if the voice is persistently hoarse, or if swallowing is difficult, these cases do not fall under the same guidelines.

Individuals who have had radiation exposure to the head or neck as children, or those with a family history of thyroid cancer, are also classified as higher risk. The same applies to individuals with certain genetic disorders.

These individuals should undergo testing not as a screening measure but as part of their medical care. What American doctors advise against is unnecessary ultrasounds, not necessary tests.

For those who have already discovered nodules during screenings in Korea, there's no need to panic. If you bring the size and ultrasound findings to your primary care physician or endocrinologist in the U.S., they will help you establish a follow-up plan.

Bringing the reports and imaging files from Korea will make comparisons much easier. The key is to see if the same nodule remains unchanged after a year.

Ultimately, the message is that more thyroid tests are not necessarily better; it's best to test those who need it when they need it. Decisions should be made in consultation with a doctor or pharmacist, considering personal and family medical history.

If I were in that situation, I would just occasionally check my neck in the mirror and feel for any changes when there are no symptoms. However, if I notice anything unusual, I would schedule an appointment right away.

The American approach of doing fewer tests may initially feel disappointing. However, after understanding the evidence behind it, I believe this approach is wiser.