Clinical Thyroidology® for the Public

Summaries for the Public from recent articles in Clinical Thyroidology
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Hypothyroidism: an underestimated issue

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Hypothyroidism is a common problem. Population-based studies from more than two decades ago estimated that about 5% of the United States population was affected by overt hypothyroidism where the TSH level is high and the FT4 level is low. When adding subclinical, or mild hypothyroidism, where the TSH level is high but the FT4 level is normal, the percent rises to 10-20%. Hypothyroidism is treated with thyroid hormone replacement, most often levothyroxine. Indeed, levothyroxine has been one of the most prescribed medications in the United States in recent years.

This study primarily aimed to provide an update as to if there has been any change to the prevalence of hypothyroidism.

Wyne KL et al 2022 Hypothyroidism prevalence in the United States: A retrospective study combining National Health and Nutrition Examination Survey and claims data, 2009-2019. J Endocr Soc 7(1):bvac172. PMID: 36466005.

The goal of this study was to use two administrative databases (2009-2012 data from the National Health and Nutrition Examination Survey [NHANES] and 2012-2019 data from the Optum claims database) to provide an update on what percent of the United States population is affected by hypothyroidism.

The study included individuals who were at least 12 years of old and not pregnant (from the NHANES database) or at least 18 years of age (from the Optum database). The authors determined whether or not individuals were affected by hypothyroidism based on available results of the thyroid hormone function tests and the presence/absence of prescription for thyroid hormone replacement.

Based on the NHANES data, the authors estimated that almost 10% of the United States population were affected with hypothyroidism between 2009-2012. Similarly, analysis of the Optum data suggest that an increasing percentage of the United States population is affected with hypothyroidism, with rates increasing from 9.5% in 2012 to 11.7% in 2019. The rate of hypothyroidism was highest among females and among those older than 60 years of age.

The study demonstrates that the percentage of United States population affected by hypothyroidism has more than doubled in the past two decades. Thus, more research is needed to understand this trend and how to best treat this patient population.

— Debbie Chen, MD


Hypothyroidism: a condition where the thyroid gland is underactive and doesn’t produce enough thyroid hormone. Treatment requires taking thyroid hormone pills.

Subclinical Hypothyroidism: a mild form of hypothyroidism where the only abnormal hormone level is an increased TSH. There is controversy as to whether this should be treated or not.

Overt Hypothyroidism: clear hypothyroidism an increased TSH and a decreased T4 level. All patients with overt hypothyroidism are usually treated with thyroid hormone pills.

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.

Thyroxine (T4): the major hormone produced by the thyroid gland. T4 gets converted to the active hormone T3 in various tissues in the body.

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.

August is Thyroid and Pregnancy Awareness Month