Occurrence of clinically relevant thyroid nodules in adults

We aimed to comprehensively investigate the occurrence of thyroid nodules in a nationally representative population as well as in women of reproductive age from a geographic area with adequate iodine intake over the last two decades.

This prospective cross-sectional study included 653 adult participants from three groups: a nationally representative gender-mixed group (205 participants) and women of reproductive age, including non-pregnant (306 participants) and pregnant (142 participants) women. For each participant, demographic data were collected, thyroid-stimulating hormone (TSH) levels were measured, thyroid volume was estimated, and the presence and size of thyroid nodules were recorded with high-resolution ultrasound. The ultrasound characteristics were analysed.

Among the nationally representative participants, nodules were detected in 44.9%, with 39.0% larger than 5 mm and 13.7% larger than 0.5 mL. Among women of reproductive age, nodules were detected in 22.5%, with 14.1% larger than 5 mm and only 2.0% greater than 0.5 mL. The prevalence and size of nodules increased significantly with age in all groups, being significantly lower in non-pregnant women than in pregnant women, who were also older. In non-pregnant women of reproductive age, the number of nodules increased significantly after the age of 25, with the number of nodules larger than 5 mm increasing only after the age of 40.

Thyroid nodules are prevalent in the population, but are rarely clinically significant. Therefore, screening for thyroid nodules in asymptomatic individuals with normal thyroid findings on clinical examination should be avoided.