Relations between sex hormones, sex hormone binding globulin, insulin-like growth factor-I and insulin-like growth factor binding protein-I in post-menopausal breast cancer patients

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Abstract
OBJECTIVE Oestrogens, androgens and anti‐endocrine drugs such as tamoxifen and aminoglutethimide influence plasma Insulin‐like growth factor‐I (IGF‐I). IGF‐I, in turn, has been found to stimulate the peripheral aromatase in vitro. The aim of this study was to examine relations between sex hormones, IGF‐I and insulin‐like growth factor binding protein‐1 (IGFBP‐1) In post‐menopausal women with breast cancer. DESIGN To measure plasma sex steroids, sex hormone binding globulin (SHBG), IGF‐I, IGFBP‐1, Insulin and urinary oestrogen metabolites In post‐menopausal women with breast cancer not receiving any endocrine therapy. PATIENTS Thirty‐two patients had fasting blood samples obtained between 0800 and 1000h. A sub‐group of 10 patients had 24‐hour urine oestrogen metabolites determined. MEASUREMENTS Plasma steroids and proteins were measured by radioImmunoassays. Urinary oestrogens were measured by GC‐MS. RESULTS SHBG correlated negatively with plasma androstenedione (P < 0·001), insulin (P < 0·001), IGF‐I, height and plasma oestrone sulphate (P < 0·025 for all), but positively with plasma IGFBP‐1 (P < 0·025). IGFBP‐1 correlated negatively with IGF‐I (P < 0·001) and the testosterone/SHBG ratio (P < 0·05). Neither IGF‐I nor IGFBP‐1 correlated with any of the plasma or urinary sex hormones or with the oestrone/androstenedione and oestradiol/testosterone ratios. Multivariate analysis revealed plasma SHBG to correlate positively with IGFBP‐1 (P= 0·029) and negatively with Insulin (P= 0·031). Plasma IGFBP‐1 correlated negatively with IGF‐I (P < 0·0001) but not with insulin. CONCLUSION Our results do not suggest any influence of plasma sex steroids in physiological concentrations on IGF‐I or IGFBP‐1 in post‐menopausal breast cancer patients, nor do they indicate IGF‐I at physiological concentrations Influences the ratios between plasma oestrogens and their androgen precursors.

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