Relative Quantification of Indium-111 Pentetreotide and Gallium-68 DOTATOC Uptake in the Thyroid Gland and Association with Thyroid Pathologies

Abstract

Recent data suggest that increased somatostatin receptor (SSTR) expression is detectable in several thyroid diseases. This raises the question as to the specificity and pathophysiologic relevance of these findings. Therefore, we systematically evaluated Indium-111 (In-111) pentetreotide scintigraphies and Gallium-68 (Ga-68) DOTA-Phe(1)-Tyr(3)-Octreotide (DOTATOC) positron emission tomography (PET) scans for thyroid radiotracer uptake. Relative binding of In-111 pentetreotide in the thyroid was measured by region of interest (ROI) technique in 4-hour and 24-hour post-injection (p.i.) planar images of 73 patients undergoing In-111 pentetreotide scintigraphy. Ga-68 DOTATOC PET scans of 77 patients were analyzed by ROI technique applied to coronal slices of 1 cm (0.39 inch) thickness with highest uptake in the thyroid region. A basal indium In-111 and Ga-68 DOTATOC uptake was found in normal thyroid glands. Hot nodules, disseminated thyroid autonomy, and most cases of active Hashimoto's disease as well as goiters and nodular thyroids showed increased In-111 pentetreotide and/or Ga-68 DOTATOC uptake. Higher relative In-111 pentetreotide uptake in the 24-hour p.i. images as compared to the 4-hour p.i. images except for patients after thyroidectomy indicates specific receptor binding in the thyroid. The increased In-111 pentetreotide and Ga-68 DOTATOC uptake in active Hashimoto's disease is most likely related to the lymphocytic infiltration of the thyroid. However, the physiologic or pathophysiologic relevance of the increased In-111 pentetreotide and Ga-68 DOTATOC uptake in normal thyroid glands, hot and cold nodules, and goiters and nodular thyroids remain to be determined.