To explore the value of octreotide suppression test(OST) in predicting the efficacy of somatostatin receptor ligands(SRLs) in the treatment of active acromegaly.

The clinical data of 76 patients with active acromegaly from 2011 to 2020 was retrospectively analyzed. OST was carried out as follows: After an overnight fasting and baseline sampling of growth hormone(GH), 100 μg octreotide was subcutaneously injected, and sampling for GH was obtained every 2 hours for 8 hours. All patients were treated with SRLs for at least 3 months. A good GH response is defined as a post-treatment random GH<1 μg/L or >80% fall compared with the baseline GH. A good insulin-like growth factor Ⅰ(IGF-Ⅰ) response is defined as IGF-Ⅰ<1.3 upper limit of normal(ULN) or >50% reduction compared with the baseline. If both GH and IGF-Ⅰ fulfill the criteria of a good response, it is defined as a good GH and IGF-Ⅰ response.

The baseline level of GH during OST was 15.00(6.38, 34.20) μg/L, the median time to reach the nadir GH was(3.65±1.65) hours, and the nadir GH level was 1.47(0.50, 4.19) μg/L. The median GH suppression rate was 89.12%(72.71%, 95.09%). When the cutoff value of GH suppression rate in predicting a good GH response was 89.32%, the area under the curve(AUC) was 0.74, with a sensitivity of 81.80% and specificity of 66.00%. When the cutoff value of GH suppression rate in predicting a good IGF-Ⅰ response was 93.14%, the AUC was 0.64, with a sensitivity of 50.00% and specificity of 75.60%. When the GH suppression rate was 90.71%, the AUC was 0.78, with the sensitivity of 83.30% and specificity of 70.00% in predicting a good GH and IGF-Ⅰ response. Compared with GH/IGF-Ⅰ non-responders, GH/IGF-Ⅰ responders displayed lower nadir GH during OST, higher GH suppression rate and IGF-Ⅰ reduction rate, and lower ratio of IGF-1 to ULN(P<0.05).

GH suppression rate during the OST is a valuable predictor to evaluate the efficacy of SRLs in patients with acromegaly, with the highest sensitivity and specificity when the cutoff value is 90.71%.

Octreotide suppression test; Long acting somatostatin receptor ligands; Acromegaly; Growth hormone suppression rate