Indium-111 pentetreotide single-photon emission tomography in patients with TSH-secreting pituitary adenomas: Correlation with the effect of a single administration of octreotide on serum TSH levels

M. Losa, P. Magnani, P. Mortini, L. Persani, S. Acerno, E. Giugni, C. Songini, F. Fazio, P. Beck-Peccoz, M. Giovanelli

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Few data are available on the visualization of somatostatin receptors in vivo in patients with thyrotropin (TSH)-secreting adenoma. We studied five patients with TSH-secreting adenomas using single-photon emission tomography (SPET) after administration of indium-111 pentetreotide. The intensity of 111In-pentetreotide uptake by the tumours was correlated with the degree of TSH suppression after a single administration of 100 μg octreotide s.c. Five patients (three women and two men) aged 27-46 years were investigated. Except for one patient with acromegaly, all had pure TSH-secreting tumours. One patient was previously untreated, while two had received octreotide, one antithyroid drugs, and one radioiodine. In all patients SPET demonstrated increased uptake of 111In-pentetreotide by the pituitary adenoma. The target to non-target ratio (T/nT) of 111In-pentetreotide uptake was higher than 10 in three patients. Administration of 100 μg octreotide s.c. caused a significant reduction in TSH levels from 4.8 ± 1.4 mU/l to a nadir of 3.1 ± 1.1 mU/l after 6 h (P <0.001 by ANOVA). Suppression of TSH secretion ranged from 30% to 60% of the baseline value. The T/nT ratio showed a trend toward a direct relationship with the degree of TSH inhibition after acute octreotide administration (r = 0.67; P = NS). Our study showed that 111In-pentetreotide scan visualized somatostatin receptors in all five of the patients with TSH-secreting pituitary adenomas, confirming the frequent presence of somatostatin receptors in these rare tumours, even though the correlation with the TSH inhibition after a single administration of octreotide did not reach significance.

Original languageEnglish
Pages (from-to)728-731
Number of pages4
JournalEuropean Journal Of Nuclear Medicine
Issue number7
Publication statusPublished - 1997



  • Hyperthyroidism
  • Octreotide
  • Pituitary neoplasm
  • Single-photon emission tomography
  • Thyrotropin

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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