Endocrine Abstracts

Background: Long-acting depot somatostatin analogues injections are useful drugs in the medical treatment of acromegaly. No previous study has assessed the value of acute octreotide suppression test in predicting responses to depot injections.

Objective: The aim of this study was to investigate the value of the acute octreotide suppression test (100 micrograms subcutaneously, GH measurements hourly for 8 hours) in predicting the long-term response to long-acting depot somatostatin analogues in patients with active acromegaly.

Method: 29 patients (21 males, 32-79 years) were subjected to the test and then were treated with lanreotide (Somatuline LA or Autogel) (n=15) or octreotide (Sandostatin LAR) (n=14). The response to treatment was evaluated 3 months later (initial). If 'safe' GH levels [mean GH in the GH day curve (GHDC) <5 milliunits per litre] were not achieved, the regime was adjusted by increasing the dose and/or shortening the injections interval until reaching 'safe' GH levels or maximun drug dose (final).

Results: The median pre-treatment GH levels were 16.0 milliunits per litre (range 3.9-137.5). The GH nadir values during the test were 2.7±2.5 (range 0.2-8.7). All patients except one suppressed GH <50% (mean 83±17%). The mean time for nadir GH was 4.0±1.8 hours (range 1-8). Nadir GH was positively correlated with mean GH in the GHDC at initial (r=0.725, p=0.001) and final response (r=0.602, p=0.002). The criterion of GH suppression <5 during the test in predicting 'safe' GH levels at initial treatment had sensitivity 100%, specificity 50% (75% for final response), positive predictive value 73.9% (95.2% for final response) and negative predictive value 100%.

Conclusion: The acute octreotide suppression test is a reliable tool for predicting responses to long-acting depot somatostatin analogues treatment in patients with acromegaly. If the GH values fall <5 milliunits per litre, there is a 74-95% chance of subsequent achieving 'safe' GH levels.