Receptor imaging with 111In-pentreotide and 123I-methoxybenzamide, and inhibition tests with octreotide and bromocriptine of mixed growth hormone/prolactin-secreting pituitary tumors.

Abstract

We have performed pituitary scintigraphy with 111In-pentreotide (OCT), a somatostatin analogue, and with metoxybenzamide (IBZM) by 123I-IBZM in two patients affected by mixed growth hormone/prolactin-secreting pituitary tumors. Short-term growth hormone (GH) inhibition by a single injection of OCT (100 micrograms s.c.), and short-term prolactin (PRL) inhibition by oral administration of 2.5 mg of bromocriptine (BCR), were also performed in both patients. The first patient, a 26 year old man, showed intense tumor uptake of 123I-IBZM scintigraphy, whereas 111In-OCT scintigraphy showed moderate tumor uptake. Five hours after the BCR inhibition test, a fall of 83% in PRL plasma levels (from 8,336 micrograms/L to 1,417 micrograms/L), and of 91.6% in GH plasma levels (from 39.5 micrograms/L to 3.3 micrograms/L) were observed. OCT inhibition test suppressed GH plasma levels from 36 micrograms/L to 3.5 micrograms/L. The patient was submitted to treatment with BCR and OCT. A dramatic shrinkage of the tumor was seen after six months of therapy. The lesion disappeared one year after the start of therapy. The second patient, a 64 year old man, showed intense uptake at 111In-OCT scintigraphy, while 123I-IBZM uptake was not observed. A test dose of BCR resulted in an acute fall of PRL (from 145 micrograms/L to 118 micrograms/L), but not of GH. A test dose of OCT decreased the GH plasma level from 61 micrograms/L to 4.5 micrograms/L. The patient was submitted to treatment with BCR and OCT that resulted in a computed tomography and magnetic resonance imaging decrease of 45% of tumor volume one year after the start of therapy. Our results suggest that both suppression tests with OCT and BCR, and scintigraphic studies in vivo with 123I-IBZM and 111In-OCT can be predictive for the effectiveness of therapies with dopamine agonists and/or SS-analogs in patients with mixed PRL/GH-secreting pituitary tumors. Further studies are required to evaluate the role of suppressive tests in selecting patients for appropriate clinical treatments.

• Authors: N Panza, P F Rambaldi, C Battista, G Ambrosio, G L Cascini, F Schillirò, L Mansi
• Journal: Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie (Biomed Pharmacother) Vol. 53 Issue 7 Pg. 319-22 (Aug 1999) ISSN: 0753-3322 [Print] France
• PMID: 10472432 (Publication Type: Case Reports, Journal Article)

Chemical References

• Benzamides
• Contrast Media
• Indium Radioisotopes
• Iodine Radioisotopes
• Pyrrolidines
• Bromocriptine
• 3-iodo-2-hydroxy-6-methoxy-N-((1-ethyl-2-pyrrolidinyl)methyl)benzamide
• Prolactin
• Growth Hormone
• Octreotide

Topics

• Adult
• Benzamides (pharmacokinetics)
• Bromocriptine (pharmacokinetics)
• Contrast Media (pharmacokinetics)
• Growth Hormone (metabolism)
• Humans
• Indium Radioisotopes
• Iodine Radioisotopes
• Magnetic Resonance Imaging
• Male
• Middle Aged
• Octreotide (pharmacokinetics)
• Pituitary Neoplasms (diagnostic imaging)
• Prolactin (metabolism)
• Pyrrolidines (pharmacokinetics)
• Radionuclide Imaging
• Tomography