Objectives: To further investigate the relationship between the plasma levels of insulin-like growth factor-1 (IGF-1), insulin-like growth factor-2 (IGF-2), insulin-like growth factor binding protein-3 (IGFBP-3), growth hormone, testosterone, and demographic factors, particularly race, within a group of men at increased risk of prostate cancer development.
Methods: Enzyme-linked immunosorbent assays or an immunosorbent assay was used to quantitate the plasma levels of IGF-1, IGF-2, IGFBP-3, growth hormone, and testosterone. The study group consisted of 169 men (85 African-American, 84 white) aged 35 to 69 years, with no personal history of prostate cancer, but having at least one first-degree relative diagnosed with the disease, unless they were African-American. The relationships between the plasma levels and the categorical covariates were assessed using the nonparametric Wilcoxon test and between the continuous variables using Spearman's correlation coefficient.
Results: The mean plasma levels of IGFBP-3 were significantly lower in African-American (2657 ng/mL) than in white (2965 ng/mL) men (P = 0.0062). The plasma levels of IGF-2 were also lower in the African-American (503.5 ng/mL) than in the white (549.1 ng/mL) men (P = 0.0084). Overall, the IGF-1 plasma levels correlated positively with the IGF-2, IGFBP-3, and growth hormone levels and the IGF-2 plasma levels correlated negatively with the testosterone levels.
Conclusions: Our results demonstrate that lower plasma levels of IGFBP-3 and IGF-2 are associated with race in a population of men at increased risk of developing prostate cancer. The ability of these markers to predict earlier disease onset is currently under investigation.