Using Growth Hormone Levels to Detect Macroadenoma in Patients with Acromegaly

BACKGROUND The aim of this study was to assess the clinical differences between acromegalic patients with microadenoma and patients with macroadenoma, and to evaluate the predictive value of growth hormone (GH) levels for early detection of macroadenoma. METHODS We performed a retrospective analysis of 215 patients diagnosed with a GH-secreting pituitary adenoma. The patients were divided into two groups: the microadenoma group and the macroadenoma group, and the clinical parameters were compared between these two groups. The most sensitive and specific GH values for predicting macroadenoma were selected using receiver operating characteristic (ROC) curves. RESULTS Compared with the microadenoma group, the macroadenoma group had a significantly younger age, higher body mass index, higher prevalence of hyperprolactinemia and hypogonadism, and a lower proportion of positive suppression to octreotide. However, there were no significant differences in the gender or in the prevalence of diabetes between the two groups. The tumor diameter was positively correlated with all GH values during the oral glucose tolerance test (OGTT). All GH values were significantly higher in the macroadenoma group than the microadenoma group. Cut-off values for GH levels at 0, 30, 60, 90, and 120 minutes for optimal discrimination between macroadenoma and microadenoma were 5.6, 5.7, 6.3, 6.0, and 5.8 ng/mL, respectively. ROC curve analysis revealed that the GH value at 30 minutes had the highest area under the curve. CONCLUSION The GH level of 5.7 ng/mL or higher at 30 minutes during OGTT could provide sufficient information to detect macroadenoma at the time of diagnosis.