Endocrine Abstracts

Background: Recently mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene have been found to occur in familial and sporadic somatotroph adenomas. These tumours tend to respond less well to somatostatin analogues, are diagnosed at an earlier age and behave more aggressively. AIP is expressed in sporadic somatotroph adenomas (Leontiou, JCEM, 2008).

Aim: To evaluate the change in AIP immunostaining in sporadic acromegaly patients treated with lanreotide prior to transsphenoidal surgery.

Methods: About 17 patients with sporadic acromegaly were treated with lanreotide 30 mg weekly or fortnightly for a 16 week period prior to transsphenoidal surgery. 17 patients, who had no pretreatment with lanreotide prior to surgery were matched for age, sex and size of tumour. The change in AIP immunostaining was measured by immunohistochemistry.

Results: After 16 weeks lanreotide treatment there was a 33.9±17.1% mean tumour volume reduction, 49.8±33.5 mU/l mean GH change (day curve) and 53.6±93.6 nmol/l mean IGF-1 change. Strong AIP immunostaining was significantly increased in the lanreotide group (60.3±19%) versus the control group (27.9±11.7%) in both sexes; P<0.001. In the lanreotide group as a whole there were no associations between AIP staining and changes in GH or IGF-1 levels, or tumour volume reduction, after lanreotide treatment. However, in female patients there was a positive correlation between AIP staining and changes in IGF-1 levels after lanreotide treatment (R=0.66, P<0.05).

Conclusion: AIP protein expression was significantly increased in sporadic acromegaly patients who were treated with lanreotide, as compared to controls. In female acromegaly patients AIP immunostaining positively correlated with changes in IGF-1 levels after lanreotide therapy. These results suggest that AIP may play a role in the mechanism of action of somatostatin analogues in sporadic acromegaly patients.