Is preoperative level of insulin-like growth factor 1 (IGF-1) connected with immunohistochemical phenotype of pituitary adenoma in patients with acromegaly?

Abstract

Background: Preoperative biochemical diagnosis of acromegaly is based on the determination of the serum levels of insulin-like growth factor 1 (IGF-1) and growth hormone (GH) in the oral glucose tolerance test. In turn, although assumptions concerning the tumour hormonal phenotype may be made on the basis of biochemical tests, the final determination of the exact adenoma profile is possible only on the basis of postoperative immunohistochemical evaluation. Due to the high importance of both – preoperative determination of the concentration of IGF-1 and postoperative immunohistochemical examination of pituitary tumour, the aim of this study was to compare these parameters. Material and methods: The study group consisted of 21 patients with acromegaly and 15 with clinically nonfunctioning pituitary adenoma (CNFPA). In all the patients IGF-1 and prolactin (PRL) concentrations in serum were measured by enzyme–amplified chemiluminescent immunoassay. The immunohistochemical diagnose of the adenoma was achieved with the primary antibodies against the pituitary hormones, the α-subunit and Ki-67 – proliferation indicator. Results: In patients with acromegaly immunohistochemistry besides monohormonal tumours – “pure” somatotropinoma, also somatoprolactinoma and adenoma plurihormonale have revealed. The mean concentrations of IGF-1 were 702, 1480 and 915 ng/mL respectively in each of these groups. In most cases the proliferation index Ki-67 was less than one. In patients with CNFPA, the IGF-1 levels were mostly in reference values and almost in half of cases the Ki–67 value was above one. Conclusions: There are statistically significant differences between preoperative serum IGF-1 concentrations in the somatoprolactinoma group and other adenoma phenotypes in acromegaly patients. This result may suggest the possible link between additional prolactin component with very high concentration of IGF-1 in patients with acromegaly.