Horm Res
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The most potent corticosteroids are 11beta-hydroxylated compounds. In humans, two cytochrome P450 isoenzymes with 11beta-hydroxylase activity, catalysing the biosynthesis of cortisol and aldosterone, are present in the adrenal cortex. CYP11B1, the gene encoding 11beta-hydroxylase (P450c11), is expressed on high levels in the zona fasciculata and is regulated by ACTH. ⋯ Molecular genetic studies are complementary; on the one hand, they have practical importance for the prenatal diagnosis of virilizing CAH forms and on the other hand, they are of theoretical importance in terms of our understanding of the functioning of cytochrome P450 enzymes. Copyrightz1999S. KargerAG, Basel
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Insulin-like growth factor (IGF)-I is an important mitogen required by some cell types to progress from the G1 phase to the S phase of the cell cycle. IGF binding proteins (IGFBPs) can have opposing actions, in part by binding IGF-I, but also by direct inhibitory effects on target cells. As mitogens and anti-apoptotic agents, IGFs may be important in carcinogenesis, possibly by increasing the risk of cellular transformation by enhancing cell turnover. ⋯ Of note, for colorectal neoplasia, fourfold elevated risks were observed in men and women with low IGFBP-3, whereas high IGF-I was associated with a doubling of risk. These emerging epidemiologic data indicate that high levels of IGF-I and low levels of IGFBP-3 are associated with an increased risk of at least several types of carcinoma that are common in economically developed countries. Further study is required to determine the clinical relevance of these findings.