Analyses of factors influencing the acute effect of octreotide in growth hormone-secreting adenomas.

Somatostatin analogues such as octreotide are used to treat active acromegalic patients by reducing serum growth hormone (GH) levels. However, the acute effect of octreotide on GH secretion differs among patients. To elucidate factors influencing the acute effect of octreotide, we collected data from 56 patients with somatotroph adenoma from two institutions. We analyzed the correlation of the following factors with the acute effect of octreotide: immunohistochemical staining of somatostatin receptor subtype 2A (SSTR 2A), presence of gsp mutation, proliferative potentials analyzed by Ki-67 staining index (SI). We found that the acute effect of octreotide significantly correlated with two factors: Ki-67 SI and the plasma membrane-dominant staining pattern of SSTR 2A. Monovariate analysis revealed a statistically significant inverse relation of Ki-67 SI with the reduction of GH by octreotide. We assessed the contribution of each factor on the acute effect of octreotide by multivariate analysis. Significant multiple regression was confirmed with p value of 0.003. Post-test revealed that the plasma membrane-dominant staining pattern of SSTR 2A was significantly related to the reduction of GH by octreotide. These results show that the acute effect of octreotide is positively related to SSTR 2A staining on the plasma membrane.