Endocrine Abstracts

Clinically non-functioning pituitary adenomas account for about one-third of pituitary tumors. The majority of them are pathologically classified as gonadotropinomas or null-cell adenomas without hormonal expression. The rest represent silent corticotroph adenomas and plurihormonal tumors. Conservative therapy with dopamine agonists and somatostatine analogues is effective in some cases only depending on the expression of somatostatine (SSTR) and dopamine 2 receptors (D2R).

Objective: The aim of this study was to quantitatively estimate SSTR2, SSTR3 and SSTR5 receptor expression in clinically non-functioning pituitary adenomas and correlate the results with immunohistochemical profile of adenoma.

Methods: Quantitative real-time RT-PCR technique.

Results: Quantitative analysis was performed in 78 clinically non-functioning pituitary adenomas for sst2, sst3 and sst5. All adenomas expressed SSTR2 and SSTR3. SSTR5 was expressed in 42% of adenomas. High variability of expression for each sst type was present. SSTR2 mRNA was expressed from 1174.8 to 146 680.8 copies/5 μl cDNA, SSTR3 62.9–46 914.3 and SSTR5 mRNA 0–43 776.6 copies/5 μl cDNA.

The median of relative quantity (after normalization to housekeeping gene) for SSTR2,3 and 5 was 5.5 and 0.3 for null-cell adenomas (SSTR5 not expressed); 0.5, 0.2 and 0.01 for gonadotrophs; 0.65, 0.1 and 0.14 in silent corticotrophs and 1.7, 0.7 and 0.05 in plurihormonal adenomas respectively.

Conclusion: SSTR2 and SSTR3 expression was not statistically different in regard to histological type of adenoma. SSTR5 expression was significantly higher in silent corticotroph adenomas. There was a correlation between SSTR2 and 3 expression. A very heterogeneous level of SSTR expression may be the reason why experimental use of somatostatine analogs and dopastatins is not clinically effective in the majority of CNFAs.

Project is supported by Ministry of Health Project No. NT/11344-4/2010.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This work was supported, however funding details unavailable.