IGF-I, IGF-II, 'free' IGF-I and IGF-binding proteins-2 to -6 during high-dose oestrogen treatment in constitutionally tall girls

Department of Pediatrics, Antwerp University Hospital, Edegem, Belgium. raoul.rooman@uza.be

OBJECTIVE: To investigate the effect of high-dose oestrogen treatment on IGF-I, IGF-II, free-dissociable IGF-I and the IGF-binding proteins (IGFBP)-2 to -6 in girls with constitutional tall stature. METHODS: In patient cohort 1, blood samples were drawn before and after 3 months of daily oral treatment with 0.1 mg ethinyloestradiol. In cohort 2, samples were collected at the end of the treatment period and 3 to 6 months afterwards. IGFs and IGFBPs were analysed by specific immunoassays and by Western ligand blot. RESULTS: Total IGF-I decreased significantly on oestrogen treatment and increased again after oestrogen withdrawal. Ligand blot analysis showed a clear reduction in a 34 kDa band, corresponding to IGFBP-2, and a strong induction of a 24 kDa band, corresponding to the non-glycosylated form of IGFBP-4. These changes were confirmed by specific immunological methods. The serum levels of IGFBP-3, IGFBP-5 and IGFBP-6 remained unchanged during the first 3 months of treatment. In cohort 2, IGFBP-3 and IGFBP-6 increased after oestrogen withdrawal. Free-dissociable IGF-I fell to 35+/-4% during oestrogen therapy and rose again when the treatment was stopped. CONCLUSIONS: Oestrogens modulate the serum concentrations of several components of the IGF system. The fall in total IGF-I is not explained by a decrease in IGFBPs but probably results from a decreased synthesis.

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				R. P A Rooman, L. O. De Beeck, M. Martin, J. van Doorn, S. Mohan, and M. V L Du Caju Ethinylestradiol and testosterone have divergent effects on circulating IGF system components in adolescents with constitutional tall stature Eur. J. Endocrinol., April 1, 2005; 152(4): 597 - 604. [Abstract] [Full Text] [PDF]