The effect of aging on the anatomic position of the thyroid gland.

Thyroid disease is common among elderly patients, frequently necessitating thyroid gland examination, imaging, and surgery. However, no prior studies have determined the effect of age on the anatomic position of the thyroid gland in the anterior neck. We hypothesized that the thyroid gland resides at a more caudal position in the neck in elderly patients as compared to younger patients. Head and neck CT scans were collected from 122 atraumatic patients without thyroid disease aged 18-39 years, 40-59 years, 60-79 years, and 80+ years. Measurements of thyroid gland position and other aspects of head and neck anatomy were conducted in the mid-sagittal plane. The distance between the thyroid gland and the sternal notch decreased from 45 ± 10.4 mm in the 18-39 age group to 30.8 ± 9 mm in the 80+ age group (P < 0.001). The position of the gland did not change significantly relative to anatomic landmarks in the head or neck, although the trachea was angled more closely to the horizontal plane in elderly patients (P < 0.001). Cervical spine height was also lower among patients ≥60 years of age compared to those <60 years of age (P < 0.001). Multivariate linear modeling suggested that thyroid gland position was dependent on changes in cervical spine height, hyoid bone to hard palate distance, and tracheal angle (P = 1.7 × 10-11 ; r2  = 0.37). Clinicians should be aware of the more caudad positioning of the gland when planning surgery or screening for thyroid disease in the elderly. Clin. Anat. 30:205-212, 2017.