We discussed the 2 published cases and describe another case of poorly-differentiated plurihormonal PIT-1 positive adenoma with moderate SSTR2 expression and intense STTR5 expression succeffuly treated with PAS-LAR 40mg/month.
RESULTS IHC of SSTR subtypes in the different cohorts showed SSTR2 staining intensity scores higher than SSTR5 in TSHoma, acromegaly and prolactinoma, whereas the expression of SSTR5 was stronger than SSTR2 in corticotropinoma and NFPA.
The mRNA expression of SSTR2 in DG-type adenomas were greater than those in SG-type adenomas and showed significantly positive correlation with GH suppression by octreotide.
No correlation between SSTR2 and SSTR5 genotypes, responsiveness to somatostatin therapy, and mRNA expression in the removed adenomas (n = 10) was found.
We quantified the expression of SSTR2 and SSTR5 mRNA using a semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) in 19 human growth hormone (GH) -secreting adenomas.
Somatostatin receptor scintigraphy was positive in most cases, and with a significantly higher uptake index in GH-producing adenomas all of which expressed SSTR2 mRNA.
In addition, the SSTR5-preferring analog showed a slight additive effect when used in combination with SSTR2 preferential drugs at submaximal concentrations in octreotide partially sensitive adenomas.
Recently, studies using somatostatin (SRIF) analogs preferential for either the SRIF receptor 2 (SSTR2) or the SSTR5 subtype demonstrated a variable suppression of GH and PRL release from GH-secreting human adenomas.
However, the expression of the gene for SSTR2 appeared not to be different between gsp + and gsp-, even when the octreotide sensitivity was significantly higher in the adenomas carrying the mutation.
However, one of the thyrotroph adenomas exhibited marked shrinkage in tumor size after octreotide therapy, in which SSTR2 mRNA was the most abundant among the adenomas examined.