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

Eur J Nucl Med. 1997 Jul;24(7):728-31. doi: 10.1007/BF00879659.


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 microg 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 microg 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.

MeSH terms

  • Adenoma / chemistry
  • Adenoma / diagnostic imaging*
  • Adenoma / metabolism*
  • Adult
  • Female
  • Hormones / pharmacology*
  • Humans
  • Indium Radioisotopes*
  • Male
  • Middle Aged
  • Octreotide / pharmacology*
  • Pituitary Neoplasms / chemistry
  • Pituitary Neoplasms / diagnostic imaging*
  • Pituitary Neoplasms / metabolism*
  • Receptors, Somatostatin / analysis*
  • Somatostatin / analogs & derivatives*
  • Thyrotropin / blood
  • Thyrotropin / drug effects
  • Thyrotropin / metabolism*
  • Tomography, Emission-Computed, Single-Photon*


  • Hormones
  • Indium Radioisotopes
  • Receptors, Somatostatin
  • Somatostatin
  • Thyrotropin
  • pentetreotide
  • Octreotide