High prevalence of differentiated thyroid carcinoma in acromegaly

Abstract

Objective: Acromegaly is a chronic disease caused by increased GH secretion and associated with a greater risk of developing both benign and malignant tumours. In the present study we evaluated the prevalence of thyroid disorders and thyroid malignancies in a series of acromegalic subjects.

Design and patients: We studied, retrospectively, a continuous series of 125 acromegalic patients referred to the Endocrinology Centres at the University Hospitals of Catania and Ferrara, Italy, over a 22-year period.

Measurements: Diagnosis and management of acromegaly were based on standardized criteria. In all patients thyroid function and morphology were evaluated by serum free T4, free T3, TSH measurements and ultrasound scanning, respectively. Fine-needle aspiration biopsy (FNAB) was performed in all solid-mixed thyroid nodules of diameter greater than 1 cm. IGF-1 expression was assessed by semiquantitative immunohistochemical analysis in some patients with differentiated thyroid cancer.

Results: Abnormal thyroid function was found in eight cases (6%). A diffuse or nodular goitre was present in 102 cases (82%). Thyroidectomy was performed in 17 patients. Histological examination revealed a differentiated thyroid cancer in seven of the patients. No significant association of thyroid cancer with GH or IGF-1 levels was found. Semiquantitative assessment of IGF-1 expression by immunohistochemistry revealed a more intense staining in thyroid cancer from acromegalic subjects than in papillary thyroid cancer from nonacromegalic subjects.

Conclusions: The frequency of thyroid disorders in our series of acromegalic subjects was similar to that previously observed in these patients. However, the prevalence of thyroid cancer was not only strikingly elevated (5.6%) in comparison to the estimated prevalence in the general population (0.093%), but it was even higher than that reported for acromegalic subjects. Sustained exposure to high serum IGF-1 levels is likely to play a role in the development of thyroid cancer in this disease. An additive role for the autocrine/paracrine action of locally produced IGF-1 is also possible. Our results suggest that thyroid function and morphology should be carefully monitored in all acromegalic patients.