Here's a recent study on lowdose 20mg Nolva(tamoxifen) and IGF. The study is on women with breast CA but the effects on IGF production should be proportionate in healthy males. Mean reduction in IGF-1 was about 17% (range of plus or minus 8%) so anywhere between a 9% and a 25% reduction. This is probably more crucial for people cyclingwith HGH in their stack.
Effect of low dose tamoxifen on the insulin-like growth factor system in healthy women.
The use of tamoxifen as a preventive agent may be limited by the increased risk of endometrial cancer and venous thromboembolic events observed in postmenopausal women. We have recently shown a comparable activity of lower doses of tamoxifen on several surrogate biomarkers of cardiovascular disease and breast cancer, including Insulin-like Growth Factor-I (IGF-I). To provide further insight into the effect of tamoxifen at low doses on the IGF system, we have correlated the drug serum levels attained after 2 months of either placebo (n = 32), tamoxifen 20 mg/day (n = 26), 10 mg/day (n = 23) or 10 mg/every other day (n = 29) with the changes in IGF-I, Insulin-like Growth Factor-II (IGF-II), Insulin-like Growth Factor Binding Protein-1 (IGFBP-1), Insulin-like Growth Factor Binding Protein-3 (IGFBP-3), and IGF-I/IGFBP-3 ratio. Compared with placebo, tamoxifen induced a mean +/- standard error (SE) reduction of IGF-I of 16.9 +/- 7.8%, p < 0.05, a non-significant increase of 22.9 +/- 12.2% in IGF-II, an increase in IGFBP-1 of 49.3 +/- 22.7%, p < 0.05, and a non-significant change of IGFBP-3 (-4.0% +/- 9.2). No significant concentration-response relationship was observed between serum tamoxifen concentrations and the biomarker changes except for the ratio of IGF-I/IGFBP-3, which decreased by 1.53 +/- 0.68% for any increase by 10 ng/ml of serum tamoxifen concentration (p = 0.02).
Breast Cancer Res Treat 2001 Sep;69(1):21-7 (ISSN: 0167-6806)
Bonanni B; Johansson H; Gandini S; Guerrieri-Gonzaga A; Torrisi R; Sandri M T; Cazzaniga M; Mora S; Robertson C; Lien E A; Decensi A
Division of Chemoprevention, European Institute of Oncology, Milan, Italy.