they are a diverse group of neoplasms that may or may not secrete hormones based on their cell of origin . in general , pituitary adenomas are frequently an invasive adenoma , which grows with invasion into the floor of the sella turcica , parasellar dura , and/or cavernous sinuses . existing therapeutic methods , including surgical removal , chemotherapy , and radiotherapy , have limited effectiveness , largely caused by the limited understanding of the molecular pathogenesis of pa . the feasibility of targeting specific pituitary cell types in vivo makes the cell - specific therapeutic approach a useful tool to treat different pituitary disorders . recombinant adenoviruses containing the gh promoter , the glycoprotein hormone -subunit promoter , the pomc promoter , and the prolactin promoter   were used to selectively drive transgene expression in specific endocrine pituitary cell populations in animal models . thyrotropin - producing pituitary adenoma ( tshoma ) is a very rare disease , representing less than 1% of all pituitary tumors . discovered in 1973 , somatostatin ( ss ) is a native inhibitory peptide hormone distributed throughout the central nervous system and peripheral tissues of the body . medical treatment of endocrine pituitary tumors with somatostatin analogs depends on somatostatin receptor ( sstr ) expression . sstr is expressed in both normal and neoplastic human pituitary cells , and sstr2 and sstr5 predominate , but the characteristic expression pattern of sstr subtypes in pituitary adenomas is tissue - specific and subtype - specific . the therapeutic effects on pituitary adenomas of somatostatin analogs like octreotide and lanreotide depends on the expression of specific somatostatin receptors on the target cells . both antihormonal and antiproliferative activity of sstrs are induced in pituitary adenomas by somatostatin analogs , and their effectiveness is limited by the development of tumor resistance . possible mechanisms of resistance include impairment or heterogeneity of sstr expression , sstr gene mutations , and decreased sensitivity of sstrs owing to uncoupling of signaling pathways . the most accepted hypothesis is the absence or reduced density of specific sstrs in the tumors , especially sstr2 and sstr5 . therefore , it would be helpful to know the expression profile of sstr subtypes in pituitary adenomas . thyrotropin ( tsh)-secreting pituitary adenomas ( tshomas ) are rare , accounting for 0.5% to 3% of all functioning pituitary adenomas . studies indicate that somatostatin analogs may control tsh secretion by interacting with sstr2 , and restrain cell proliferation by interacting with sstr5 [ 1719 ] . however , these results were acquired from a limited number of patients and will require further validation . has recently found that a high sst(5)/sst(2 ) ratio might be predictive of a positive outcome to long - term treatment with somatostatin analogs in tshomas . moreover , combined somatostatin and d(2 ) receptor targeting might be a potential tool to improve the response rate in octreotide - resistant tumors . to the best of our knowledge , the expression of sstr2 and sstr5 in tshoma has been demonstrated by ihc in only a few patients . highly specific antibodies can confirm the expression of sstr subtype proteins , but heterogeneity of tumors and the use of different detection methods often lead to inconsistency in the reported expression of sstr subtypes in different types of pituitary tumors [ 12,2126 ] . because it is clinically meaningful to identify the expression profiles of sstr subtypes in pituitary adenomas , we investigated the expression of sstr2 and sstr5 in a series of patients with tshoma and other pituitary adenomas , as well as the association of sstrs expression with efficacy of short - term oct treatment . we enrolled tshoma patients enrolled who were newly diagnosed and previously untreated , while those with primary hyperthyroidism or resistance to thyroid hormone syndrome were excluded . all patients had undergone surgery at yuhuangding hospital , between january 1999 and june 2015 . the diagnosis was based on a combination of clinical manifestations , biochemical assessments of pituitary function , findings of pituitary imaging , and pathological evaluation . on this basis , 16 patients with tshoma were identified and enrolled in the study . those with acromegaly , corticotropinoma , prolactinoma , or nonfunctioning pituitary adenomas ( nfpa ) the sex , age at diagnosis , pathological diagnosis , tumor size , and date of the last follow - up of each participant were collected from medical records . octreotide used in this investigation came from novartis pharmaceuticals corporation ( east hanover , nj , usa ) . each patient received an initial dose of 100 g , injected subcutaneously at 8 : 00 a.m. if the patient showed no obvious side effects ( such as nausea , vomiting , stomach ache and diarrhea ) , their dosages were increased to 100 g 2 or 3 times / day . serum tsh , ft3 , ft4 , tt3 , and tt4 concentrations were measured by chemiluminescent enzyme assays using commercially available kits . we used the formula : tsh suppression rate ( % ) = [ ( before treatment tsh value - after treatment tsh value)/before treatment tsh value]100 . all tissue specimens of the patients were obtained during pituitary surgery , fixed in 4% paraformaldehyde overnight , routinely processed , and embedded in paraffin . for adenoma classification , the specimens were cut into 4-m - thick sections and stained with hematoxylin and eosin and periodic acid schiff ( pas ) staining protocol . ich staining with monoclonal antibodies against the specific pituitary hormones , including tsh , growth hormone ( gh ) , prolactin ( prl ) , acth ( adrenocorticotropic hormone ) , luteinizing hormone ( lh ) , and follicle - stimulating hormone ( fsh ) , were also carried out on the tumor tissues . the pathological diagnoses were verified by experienced pathologists following the 2004 world health organization classification . formalin - fixed slides were prepared in unstained 3-m sections and a 48-dot core ( diameter 2.0 mm ) matrix chip template . immunohistochemical staining was performed with a leica bond - iii , automatic ihc and ish stainer ( leica biosystems , nussloch , germany ) , which is an automatic and continuous access slide - staining system that simultaneously processes ihc protocols , with a 10-min heat - induced epitope retrieval and a 15-min antibody incubation . the primary sstr2 antibody was ab13120 ( 1 : 100 ) , and the primary sstr5 antibody was ab13121 ( 1 : 100 ; abcam , cambridge , uk ) . the preparation and evaluation of the tissues were performed at the department of neuropathology , beijing tiantan hospital , capital medical university . the sections were assessed independently by 2 experienced pathologists who were blinded to both the clinical and the pathology data . the scoring of each section was determined by consensus and followed the immunoreactive score ( irs ) method described by remmele et al . . the irs was calculated by multiplying the staining intensity ( 0=no staining , 1=weak staining , 2=moderate staining , 3=strong staining ) by the percentage of positively stained cells ( 0=0% , 1=1% to 33% , 2=33% to 66% , and 3 66% ) . the resulting irs scores ranged from 0 ( no staining ) to 9 ( maximum staining ) . irs scores of 0 were negative , 12 were low , 34 were intermediate , 57 were high - intermediate , and 89 were high . the data were statistically analyzed using spss software version 20.0 for windows ( spss , chicago , il ) . data of normal distribution were reported as means  standard error ( se ) . otherwise , the data are reported as medians and ranges ( minimum  maximum ) . multiple linear regression was used for analyzing factors for efficacy of short - term preoperative oct treatment , and the wilcoxon rank sum test was used to compare the 2 groups . we enrolled tshoma patients enrolled who were newly diagnosed and previously untreated , while those with primary hyperthyroidism or resistance to thyroid hormone syndrome were excluded . all patients had undergone surgery at yuhuangding hospital , between january 1999 and june 2015 . the diagnosis was based on a combination of clinical manifestations , biochemical assessments of pituitary function , findings of pituitary imaging , and pathological evaluation . on this basis , 16 patients with tshoma were identified and enrolled in the study . those with acromegaly , corticotropinoma , prolactinoma , or nonfunctioning pituitary adenomas ( nfpa ) the sex , age at diagnosis , pathological diagnosis , tumor size , and date of the last follow - up of each participant were collected from medical records . octreotide used in this investigation came from novartis pharmaceuticals corporation ( east hanover , nj , usa ) . each patient received an initial dose of 100 g , injected subcutaneously at 8 : 00 a.m. if the patient showed no obvious side effects ( such as nausea , vomiting , stomach ache and diarrhea ) , their dosages were increased to 100 g 2 or 3 times / day . serum tsh , ft3 , ft4 , tt3 , and tt4 concentrations were measured by chemiluminescent enzyme assays using commercially available kits . we used the formula : tsh suppression rate ( % ) = [ ( before treatment tsh value - after treatment tsh value)/before treatment tsh value]100 . all tissue specimens of the patients were obtained during pituitary surgery , fixed in 4% paraformaldehyde overnight , routinely processed , and embedded in paraffin . for adenoma classification , the specimens were cut into 4-m - thick sections and stained with hematoxylin and eosin and periodic acid schiff ( pas ) staining protocol . ich staining with monoclonal antibodies against the specific pituitary hormones , including tsh , growth hormone ( gh ) , prolactin ( prl ) , acth ( adrenocorticotropic hormone ) , luteinizing hormone ( lh ) , and follicle - stimulating hormone ( fsh ) , were also carried out on the tumor tissues . the pathological diagnoses were verified by experienced pathologists following the 2004 world health organization classification . formalin - fixed slides were prepared in unstained 3-m sections and a 48-dot core ( diameter 2.0 mm ) matrix chip template . immunohistochemical staining was performed with a leica bond - iii , automatic ihc and ish stainer ( leica biosystems , nussloch , germany ) , which is an automatic and continuous access slide - staining system that simultaneously processes ihc protocols , with a 10-min heat - induced epitope retrieval and a 15-min antibody incubation . the primary sstr2 antibody was ab13120 ( 1 : 100 ) , and the primary sstr5 antibody was ab13121 ( 1 : 100 ; abcam , cambridge , uk ) . the preparation and evaluation of the tissues were performed at the department of neuropathology , beijing tiantan hospital , capital medical university . the sections were assessed independently by 2 experienced pathologists who were blinded to both the clinical and the pathology data . the scoring of each section was determined by consensus and followed the immunoreactive score ( irs ) method described by remmele et al . . the irs was calculated by multiplying the staining intensity ( 0=no staining , 1=weak staining , 2=moderate staining , 3=strong staining ) by the percentage of positively stained cells ( 0=0% , 1=1% to 33% , 2=33% to 66% , and 3 66% ) . the resulting irs scores ranged from 0 ( no staining ) to 9 ( maximum staining ) . irs scores of 0 were negative , 12 were low , 34 were intermediate , 57 were high - intermediate , and 89 were high . the data were statistically analyzed using spss software version 20.0 for windows ( spss , chicago , il ) . data of normal distribution were reported as means  standard error ( se ) . otherwise , the data are reported as medians and ranges ( minimum  maximum ) . multiple linear regression was used for analyzing factors for efficacy of short - term preoperative oct treatment , and the wilcoxon rank sum test was used to compare the 2 groups . as shown in table 1 , in addition to the 16 patients with tshoma , we also included 8 with acromegaly , 3with prolactinoma , 3 with corticotropinoma , and 4 with clinical nfpa . tumors over 10 mm were defined as macroadenomas , and those smaller than 10 mm as microadenomas . we identified 16 tshoma patients ( 11 men and 5 women ) with a mean age of 33 years ( range : 1751 years ) . eight were acromegalic patients ( 4 men and 4 women ) with a mean age of 33 years ( range : 1239 years ) ; 1 with microadenoma and 7 with macroadenomas . three patients had cushing disease , who were all women , with a mean age of 45 years ( range : 3853 years ) ; 1 had a microadenoma and 2 had macroadenomas . three patients had prolactinomas , who were all women , with a mean age of 47 years ( range : 3164 years ) , and all had macroadenomas . four patients had nfpas ( 3 men and 1 woman ) , with a mean age of 45 years ( range : 3165 years ) , and all had macroadenomas . the diagnosis of functional pituitary adenoma was based on clinical manifestations , hormone levels , and imaging results , and confirmed by pathological evidence ( figure 1 ) . the immunohistochemistry of sstr2 and sstr5 was positive in the membrane staining , as shown in figures 2 and 3 . the immunostaining pattern in tshoma was sstr2>sstr5 , with 15 of 16 specimens ( 93.7% ) having high sstr2 irc scores and only 1 specimen having a high - intermediate score . the sstr5 irs scores were high - intermediate in 8 specimens ( 50% ) , intermediate in 4 ( 25% ) , and low in 4 ( 25% ) . ihc staining ( table 2 ) demonstrated that , in acromegaly , sstr2 expression was more frequent and stronger than sstr5 expression . high irc scores were seen for sstr2 in 6 of the 8 acromegaly specimens ( 75% ) , with low and intermediate intensity staining in the remaining 2 specimens ( 12.5% each ) . high - intermediate sstr5 staining intensity was seen in 2 of the 8 acromegaly specimens ( 25% ) ; while low and intermediate staining intensity was found in 3 of the 8 ( 37.5% each ) . the 3 prolactinoma specimens had different sstr2 ( low , intermediate , and high - intermediate ) and sstr5 ( low , intermediate , and high ) staining intensities . high - intermediate sstr2 staining intensity was seen in 1 of the 3 corticotropinoma specimens , while the remaining 2 were negative . sstr5 staining was also found to be different in each of the corticotropinoma specimens ( low , intermediate , and high - intermediate ) . all the 4 nfpa specimens were negative for sstr2 expression ; high - intermediate sstr5 staining was observed in 1 ( 25.0% ) and the remaining 3 were negative . in normal pituitary tissues , sstr2 expression was high - intermediate in 2 of the 4 samples tested and intermediate in 2 . two of the specimens had high - intermediate sstr5 expression , and the other 2 were negative . short - term preoperative oct administration was highly effective in normalizing excessive hormone concentrations , with tolerable adverse effects as well . following oct treatments for a median of 8.4 days ( range : 318 days ) and with a total median dose of 1.9 mg ( range : 0.94.2 mg ) , all patients presented significant decreases of tsh and thyroid hormone levels ( tsh [ iu / ml ] : 4.953.59 to 0.921.55 [ t=4.721 , p=0.000 ] ; ft3 [ pmol / l ] : 11.778.69 to 4.170.88 [ t=3.507 , p=0.003 ] ; ft4 [ pmol / l ] 29.568.51 to 16.724.13 [ t=6.662 , p=0.000 ] ( table 3 ) . reference ranges are tsh : 0.354.94 iu / ml ; ft3 : 2.635.7 pmol / l ; ft4 : 9.0019.04 pmol / l . safety of treatment with sst analogs was proven ; no patients discontinued treatment due to unbearable adverse effects . linear regression analysis found no statistically significant difference between the tsh suppression rate and general characteristics ( age or sex ) , tumor size ( micro - or macro adenoma ) , and sstrs expression . with irs scores categorized as low expression ( 04 ) and high expression ( 59 ) , we analyzed the relationship between tsh suppression rate and sstr5 expression with the 2 independent - samples wilcoxon rank sum test . the results showed p value=0.002 , which is statistically significant , suggesting that sstr5 expression may be related to the efficacy of short - term oct therapy . as shown in table 1 , in addition to the 16 patients with tshoma , we also included 8 with acromegaly , 3with prolactinoma , 3 with corticotropinoma , and 4 with clinical nfpa . tumors over 10 mm were defined as macroadenomas , and those smaller than 10 mm as microadenomas . we identified 16 tshoma patients ( 11 men and 5 women ) with a mean age of 33 years ( range : 1751 years ) . eight were acromegalic patients ( 4 men and 4 women ) with a mean age of 33 years ( range : 1239 years ) ; 1 with microadenoma and 7 with macroadenomas . three patients had cushing disease , who were all women , with a mean age of 45 years ( range : 3853 years ) ; 1 had a microadenoma and 2 had macroadenomas . three patients had prolactinomas , who were all women , with a mean age of 47 years ( range : 3164 years ) , and all had macroadenomas . four patients had nfpas ( 3 men and 1 woman ) , with a mean age of 45 years ( range : 3165 years ) , and all had macroadenomas . the diagnosis of functional pituitary adenoma was based on clinical manifestations , hormone levels , and imaging results , and confirmed by pathological evidence ( figure 1 ) . the immunohistochemistry of sstr2 and sstr5 was positive in the membrane staining , as shown in figures 2 and 3 . the immunostaining pattern in tshoma was sstr2>sstr5 , with 15 of 16 specimens ( 93.7% ) having high sstr2 irc scores and only 1 specimen having a high - intermediate score . the sstr5 irs scores were high - intermediate in 8 specimens ( 50% ) , intermediate in 4 ( 25% ) , and low in 4 ( 25% ) . ihc staining ( table 2 ) demonstrated that , in acromegaly , sstr2 expression was more frequent and stronger than sstr5 expression . high irc scores were seen for sstr2 in 6 of the 8 acromegaly specimens ( 75% ) , with low and intermediate intensity staining in the remaining 2 specimens ( 12.5% each ) . high - intermediate sstr5 staining intensity was seen in 2 of the 8 acromegaly specimens ( 25% ) ; while low and intermediate staining intensity was found in 3 of the 8 ( 37.5% each ) . the 3 prolactinoma specimens had different sstr2 ( low , intermediate , and high - intermediate ) and sstr5 ( low , intermediate , and high ) staining intensities . high - intermediate sstr2 staining intensity was seen in 1 of the 3 corticotropinoma specimens , while the remaining 2 were negative . sstr5 staining was also found to be different in each of the corticotropinoma specimens ( low , intermediate , and high - intermediate ) . all the 4 nfpa specimens were negative for sstr2 expression ; high - intermediate sstr5 staining was observed in 1 ( 25.0% ) and the remaining 3 were negative . in normal pituitary tissues , sstr2 expression was high - intermediate in 2 of the 4 samples tested and intermediate in 2 . two of the specimens had high - intermediate sstr5 expression , and the other 2 were negative . short - term preoperative oct administration was highly effective in normalizing excessive hormone concentrations , with tolerable adverse effects as well . following oct treatments for a median of 8.4 days ( range : 318 days ) and with a total median dose of 1.9 mg ( range : 0.94.2 mg ) , all patients presented significant decreases of tsh and thyroid hormone levels ( tsh [ iu / ml ] : 4.953.59 to 0.921.55 [ t=4.721 , p=0.000 ] ; ft3 [ pmol / l ] : 11.778.69 to 4.170.88 [ t=3.507 , p=0.003 ] ; ft4 [ pmol / l ] 29.568.51 to 16.724.13 [ t=6.662 , p=0.000 ] ( table 3 ) . reference ranges are tsh : 0.354.94 iu / ml ; ft3 : 2.635.7 pmol / l ; ft4 : 9.0019.04 pmol / l . safety of treatment with sst analogs was proven ; no patients discontinued treatment due to unbearable adverse effects . linear regression analysis found no statistically significant difference between the tsh suppression rate and general characteristics ( age or sex ) , tumor size ( micro - or macro adenoma ) , and sstrs expression . with irs scores categorized as low expression ( 04 ) and high expression ( 59 ) , we analyzed the relationship between tsh suppression rate and sstr5 expression with the 2 independent - samples wilcoxon rank sum test . the results showed p value=0.002 , which is statistically significant , suggesting that sstr5 expression may be related to the efficacy of short - term oct therapy . quantitative real - time polymerase chain reaction ( rt - pcr ) and western blot assays were used to describe the expression profiles of sstr subtypes in pituitary adenomas . quantitative rt - pcr might overestimate the actual percentage of tumors expressing sstr subtypes because immune , stromal , and normal tissue cells , as well as blood vessels that are present in or surrounding the tumors , might also express sstr subtypes . most reports publicly available focused on tumor types other than growth hormone - secreting adenomas , especially tshoma , and many of these are case reports or are limited to assays of rna expression . studies have reported that abnormal mir-26a , cold - inducible rna - binding protein ( cirp ) , and cyclooxygenase-2 ( cox-2 ) expression play a major role in pituitary tumorigenesis , recurrence , and invasiveness [ 3032 ] . somatostatin peptides bind to the sstrs expressed on the cells of the target tissues , exerting a series of biological effects . in the central nervous system the immunohistochemical method performed on surgically removed tumor tissue reveals the expression of receptor proteins and demonstrates their cellular localization . although immunohistochemical methods can detect receptor proteins and show the subcellular localization of the receptors , they are rarely used to study the expression of sstr subtypes because of a lack of well - characterized sstr subtype - specific antibodies . developed a series of mouse monoclonal antibodies with high specificity for the 5 sstr subtypes and no cross - reactivity with ihc staining . few of these studies investigated ihc . in the present study , however , we assessed the expression profiles of sstr2 and sstr5 in pituitary adenomas by ihc technique , and found significant differences in the expression and distribution of sstr subtypes in various adenomas . it was previously shown by rt - pcr in a single fetal pituitary ( 14 wk ) that all 5 human sstr subtype mrnas were expressed . shimon et al . reported that using reverse transcription - pcr , mrna expression of sstr2 and sstr5 were detected in fetal pituitary by 25 weeks . in our study , 2 normal pituitaries collected from the donor s head did not express sstr5 . this may be because the different detection methods that we used lead to disparate test results . previous studies enrolled patient cohorts with compositions different from ours , which might have resulted in different sstr subtype expression profiles . for example , pisarek et al .   found that the pattern of sstr immunostaining in acromegaly was sstr 5>sstr 1>sstr 2a = sstr 3>sstr 2b . used immunohistochemistry to study the expression of sstr subtypes in tmas and qpcr to compare absolute mrna copy numbers for all 5 sstr isoforms in 23 somatotrophinomas , and found that expression was sstr5>sstr2a > sstr2b . .   found that in somatotrophinomas , expression of subtype sstr5 mrna was the highest , followed by sstr2=sstr3=sstr1=sstr4 . some previous ihc studies also found high sstr2 and low sstr5 immunoreactivity in cushing s disease ; others have reported low expression of sstr2 mrna in patients with cushing s disease [ 3542 ] . low expression of sstr2 and sstr5 mrna was reported in a sample of 19 nfpas , while sstr3 expression was high and predominant in more than half of the tumors . some studies have also reported high expression of both sstr3 and sstr2 mrna in nfpas . found that sstr3 had the highest expression level followed by sstr2 in a series of 15 nfpas , and pisarek et al .   reported an expression pattern of sstr2b > sstr2a > sstr5 in a group of 22 nfpas . because most prolactinomas are responsive to treatment with dopamine agonists , specimens are seldom available . reported an ihc staining pattern of sstr 2b = sstr 3=sstr 5>sstr 1=sstr 2a in prolactinomas . among the 3 prolactin secreting adenomas in our series , expression of sstr2 was stronger than that of sstr5 . tshoma is a very rare disease , with few reports of the relative expression of sstr subtypes . horiguchi et al .   reported an mrna expression pattern of sstr2a > sstr1>sstr5>sstr3 in a series of tsh - secreting adenomas compared with expression in normal pituitary tissue . overall , the results of the present study are not completely consistent with existing research findings . possible explanations include the small sample size and population - related differences , as all the patients in our study were chinese , while data of other studies were obtained from white patients . most ( 80% ) tshoma patients have macro - adenomas , with microadenomas thus being exceptional . tshomas are often large and invasive lesions and highly fibrous , which hampers complete removal . as for medical therapy , somatostatin analogs are reported to inhibit tsh secretion in addition to tumor growth in combination with the surgical or radiological therapy . our study found short - term preoperative oct can control tsh and thyroid hormone levels . however , the relationship between the response to oct and expression of subtype - specific sstrs in tumor tissues has yet to be clarified . tsh secretion is mediated via interactions with sstr2 and tumor size reduction via interactions with sstr5 . in our study short - term response to oct therapy may be related to the expression of sstr5 . however , additional studies with larger numbers of cases are necessary to establish the sstr5 expression spectrum in pituitary adenoma and the role of sstrs in oct therapy for tshoma . tsh - secreting pituitary adenomas preferentially express sstr2 , with higher sstr2 ihc staining intensity scores as compared to sstr5 . in addition , the patients with tshoma had stronger expression of sstr2 and a higher prevalence of sstr5 expression as compared to patients with the other types of pituitary adenomas . sstr2 and sstr5-preferring octreotide and lanreotide may be a useful treatment approach , especially in tshoma or somatotropinoma patients . therefore , immunohistochemical staining for detection of sstr subtypes is recommended for all surgical specimens .
backgroundthyrotropin - secreting pituitary adenomas ( tshomas ) are a rare cause of hyperthyroidism . 
 somatostatin analogs have proved to be effective for inhibiting pituitary hormones secretion , working via interactions with somatostatin receptors ( sstrs ) . moreover , 
 antiproliferative activity of somatostatin analog is now demonstrated in several studies . in the present study 
 , we determined the relative predominance of sstr2 and sstr5 subtypes among the different types of adenomas , especially tshoma , and investigated the relationship between efficacy of short - term octreotide ( oct ) treatment and sstr expression.material/methodsserum hormone determinations and histological findings in resected tissue resulted in 5 diagnoses : 16 tshomas , 8 acromegaly , 3 prolactinomas , 3 corticotropinomas , 4 clinically nonfunctioning adenomas ( nfpas ) , and 4 normal pituitary specimens . 
 ihc was performed on formalin - fixed and paraffin - embedded tissue in tissue microarrays.resultsihc 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 . 
 sstr2 and sstr5 expressions were significantly higher in tshoma than in other pituitary adenomas . 
 oct treatment for a median of 8.4 days ( range : 318 days ) and with a total median dose of 1.9 mg ( range : 0.94.2 mg ) showed a significant decrease of thyroid hormone levels ( tsh [ iu / ml ] in all patients . 
 patients with low sstr5 expression presented a significantly higher tsh suppression rate ( p values < 0.05).conclusionsthe present data confirm that somatostatin analogs should be considered as a medical alternative to surgical treatment , especially in patients with tshoma , and short - term response to oct therapy may be related to the expression of sstr5 .