High-frequency ultrasound examination of the thyroid was performed in 253 subjects (130 women and 123 men; age range, 19-50 years) that were randomly selected from the population in an area of Finland where goiter is not endemic. Thyroid echo abnormalities were detected in 69 subjects (27.3%). Prevalence of abnormalities increased with age, and women showed more lesions than did men in each of the 3 decades. The abnormality was solitary in 39 subjects (57%), multiple in 15 (22%), and diffuse in 15 (22%). Of the 68 individual nodules, 48 (70%) were smaller than 1 cm in diameter. Anechoic rounded nodules 1-5 mm in diameter were found in 28 subjects. Fine-needle aspiration biopsy was performed in 30 subjects. Cytologic examination revealed no unequivocal malignancies. In eight subjects (3.2%) with a diffuse echo abnormality, cytologic evaluation indicated lymphocytic thyroiditis. It is concluded that the prevalence of small thyroid echo abnormalities in a randomly selected adult population is rather high, a fact that supports use of a conservative approach to these types of findings.

Thyroid US abnormalities occurring in a random adult population are predominantly benign and clinically unimportant.

To determine the prevalence of thyroid nodules in the healthy population, ultrasonography (US) of the thyroid gland was performed in 101 women aged 49-58 years in an urban area in southern Finland where goiter is not considered endemic. Subjects with any previous thyroid disease were excluded. Thyroid nodules or abnormalities of the echo structure were found in 36 (35.6%) subjects. Seventeen (47.2%) subjects had solitary nodules, 14 (38.9%) had multiple nodules, and five (13.9%) had diffuse abnormalities. Subjects with abnormal findings at US were further examined with fine-needle aspiration biopsy. Clinical examination and blood tests were performed for evaluation of levels of thyroxine, thyroid-stimulating hormone, and thyroid antibodies. One patient had a leukemic thyroid nodule, but no primary thyroid malignancies were found. In most cases, cytologic findings were benign and nonspecific, with a variable amount of degenerative changes. Three atoxic multinodular goiters and two cases of Hashimoto thyroiditis were detected. The results are in accordance with autopsy studies indicating that focal nodular changes of the thyroid gland are common in middle-aged women.

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