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.
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.
Losa
M
M
Department of Neurosurgery, IRCCS San Raffaele, University of Milan, Italy.
Magnani
P
P
Mortini
P
P
Persani
L
L
Acerno
S
S
Giugni
E
E
Songini
C
C
Fazio
F
F
Beck-Peccoz
P
P
Giovanelli
M
M
D000236:Adenoma / Q000737:chemistry / Q000000981:diagnostic imaging* / Q000378:metabolism*; D000328:Adult; D005260:Female; D006728:Hormones / Q000494:pharmacology*; D006801:Humans; D007205:Indium Radioisotopes; D008297:Male; D008875:Middle Aged; D015282:Octreotide / Q000494:pharmacology*; D010911:Pituitary Neoplasms / Q000737:chemistry / Q000000981:diagnostic imaging* / Q000378:metabolism*; D017481:Receptors, Somatostatin / Q000032:analysis*; D013004:Somatostatin / Q000031:analogs & derivatives*; D013972:Thyrotropin / Q000097:blood / Q000187:drug effects / Q000378:metabolism*; D015899:Tomography, Emission-Computed, Single-Photon
D006728:Hormones; D007205:Indium Radioisotopes; D017481:Receptors, Somatostatin; D013004:Somatostatin; D013972:Thyrotropin; C081788:pentetreotide; D015282:Octreotide