Goiter associated with acromegaly: sonographic and scintigraphic findings of the thyroid gland

Elevation in serum human growth hormone (GH) level is known to be a factor that causes goiter development. The present study was designed to analyze sonographic and scintigraphic appearances of the thyroid in patients with acromegaly. The records of 48 consecutive patients with acromegaly were examined. Two patients had a history of operation for thyroid cancer. One had an atrophic thyroid gland after 131I treatment for Graves' disease. Goiter was palpable in 39 of the remaining 45 patients. Neither ultrasonography (US) nor scintigraphy was performed in 17 patients, including 6 with no palpable goiter and 11 with small diffuse goiter (group 1). Of the remaining 28 patients who underwent US, 14 had a moderately or markedly enlarged diffuse goiter (group 2), 13 were diagnosed as having adenomatous goiter (group 3), and 1 had a solitary cystic nodule. Among 11 patients in group 3 who underwent 123I or 99mTc thyroid scintigraphy, 6 showed uneven uptake, and 2 with undetectably reduced levels of thyrotropin (TSH) showed localized functioning areas. The mean serum TSH concentration in group 3 was significantly lower than that in group 1 or 2 (p<0.01). The duration of illness as acromegaly was significantly longer in group 2 and 3 as compared with group 1 (p<0.05). These results suggest that long-term stimulation by GH and insulin-like growth factor-I of thyroid follicular cells might be responsible for thyroid enlargement, presence of functioning lesions, slight overactivity of the thyroid, and the subsequent formation of multiple nodules in acromegalic patients. In conclusion, excluding two patients with thyroid cancer and one with Graves' disease, goiter was palpable in 39 of the 45 patients with acromegaly, among whom 14 (13 adenomatous goiters and 1 solitary cystic nodule) showed nodular enlargement.