Production and secretion of immunoreactive growth hormone-releasing factor by pheochromocytomas

The production and secretion of immunoreactive growth hormone-releasing factor (IR-GRF) by pheochromocytomas were examined immunohistochemically and immunochemically. GRF-immunoreactive (GRF-IR) cells were found, although sparsely, in 2 of 13 tumors (Cases 1 and 2), while somatostatin (SRIF)-IR cells and vasoactive intestinal peptide (VIP)-IR cells were found in nine and five tumors, respectively. Concentrations of tissue IR-GRF of 29.8 and 17.2 ng/g wet weight tissue, respectively, were found in two (Cases 1 and 2) of three tumors examined. These three tumors also contained IR-SRIF at 19.5-105.5 ng/g wet weight tissue and IR-VIP at 13.6-24.8 ng/g wet weight tissue. An increased plasma IR-GRF concentration (30.0 pg/ml) was found in a blood sample taken from the inferior vena cava near the adrenal tumor in Case 1. This is the first report that some pheochromocytomas produce GRF and secrete it into the blood circulation.