RIA data for the levels of circulating IGF-I and IGFBP-1 for (□) normal individuals, () patients with secondary erythrocytosis (E), and (▪) patients with PV are shown as the mean ± standard error of the mean. Values are given in micrograms per liter for IGF-I (n = 3 for normal, n = 6 for E, and n = 4 for PV) and in micrograms per liter × 10−1 for IGFBP-1 (n = 3 for normal, n = 7 for E, and n = 4 for PV). The level of IGF-I in PV was not different from those in patients with secondary erythrocytosis or normals (.2 < P < .1 and .5 < P < .4, respectively). In contrast, IGFBP-1 levels were significantly higher in PV compared with either patients with secondary erythrocytosis or normal individuals (P < .001). Therefore, IGFBP-1 appeared to be specifically elevated in patients with PV.
