The predictive value of an acute octreotide suppression test in patients with acromegaly

• Main Authors: Mateja Strinović, Jelena Marinković Radošević, Gorana Mirošević, Hrvoje Ivan Pećina, Vatroslav Čerina, Leo Pažanin, Milan Vrkljan
• Format: Article
• Language: English
• Published: VBZ 2015-12-01
• Series: Endocrine Oncology and Metabolism
• Subjects: acromegaly; somatostatin; somatostatin analogues; acute octreotide tes; acute octreotide test
• Online Access: http://eom.hdeo.eu/wp-content/uploads/2017/02/vol1-iss1-4Strinovic.pdf
• ISSN: 1849-8922; 1849-9031

Acromegaly is a rare chronic disorder that is in 95% of cases caused by growth hormone (GH) secreting pituitary tumors. Endonasal transphenoidal surgery is usually considered the first line of treatment, followed by medical therapy for residual disease. The long-acting somatostatin (SA) analogues have an important role in the medical treatment of these patients. SA exert their biological effects by activating somatostatin receptors (SSTR). The predominant types of SSTR receptors in GH-secreting pituitary tumors are subtypes 2 (SSTR2) and 5 (SSTR5). The efficacy of somatostatin analog therapy (SAT) is determined by its effect on tumor shrinkage which is reported to be between 20 and 50%. Approximately 10-30% of GH-secreting pituitary tumors are resistant to SA because of variable or reduced tumoral expression of SSTR2 or SSTR5. In many centres a test dose (TD) of octreotide is administered before commencing SAT in order to predict the long term response to treatment. There has been a great interest in identifying factors that predict a good response to SAT. To date, several studies that have examined the relationship between the TD of octreotide and SAT. It is crucial how we define response during the OST. Nadir of GH to 5mU/l or less during the OST has an excelent predictive value for evaluation of long-term response to SAT. On the other hand, if we define response as percentage of change of GH from it’s baseline values, then the OST is not usefull diagnostic test.