Oestrogens inhibition

EGF-RTK [antibacterial, antifungal, oestrogenic inhibits EST-R positive breast cancer cell proliferation] EGF-RTK (19) (uncoupler)... 

Oestrogen inhibits the age-related loss of bone that occurs in most women after menopause. Observational studies have indicated that the use of oestrogen reduces the risk of vertebral fracture by approximately 50% and the risk of hip fracture by 25-30%. Unopposed oestrogen increases by 10-fold the risk of endometrial cancer, which is diminished by added progestogen. Therefore combinations of oestrogen and progestogen are the mainstay of treatment for postmenopausal osteoporosis they inhibit the rapid bone loss that occurs immediately after the menopause and should be continued for 5 years. 

There is a clear correlation between adiposity and breast cancer, which is almost certainly due to synthesis of oestradiol in adipose tissue enterolactone and some of the other flavonoid phyto-oestrogens inhibit aromatase and will therefore reduce synthesis of oestradiol in adipose tissue. 

Genistein (but not other phyto-oestrogens) inhibits cell proliferation by inhibiting the tyrosine kinase activity of the epithelial growth factor receptor. 

KAO Y c, ZHOU c, SHERMAN M, LAUGHTON 0 A, CHEN s (1998) Molecular basis of the inhibition of human aromatase (oestrogen synthetase) by flavone and isoflavone phytoestrogens a site-directed mutagenesis study. Environ Health Perspect. 106 85-92. 

Terakawa N, Shimizu I, Aono T, Tanizawa O, Matsumoto K (1986) Dexamethasone inhibits the effects of oestrogen on the pituitary gland in rats. Acta Endocrinol 112 64-70... 

F8. Fotsis, T., Zhang, T., Pepper, M. S., Adlercreutz, H., Montesano, R., Nawroth, P. P., and Schwergerer, L., The endogenous oestrogen metabolite 2-methoxyoestradiol inhibits angiogenesis and suppresses tumour growth. Nature (London) 368, 237-239 (1994). 

Drugs that can be used to control tumour cell proliferation inhibit a variety of enzymes, including thymidylate synthase and topoisomerase (Chapter 20). The enzyme aromatase converts a ring in a steroid to an aromatic ring. It converts, for example, adrenal steroid hormones into female sex hormones, which bind to oestrogenic receptors in the ovary or breast and increase the risk of ovarian or breast cancer. Aromatase inhibitors are used to treat patients with breast or ovarian cancers that are sensitive to oestrogen. Unfortunately, none of the inhibitors is specific for enzymes in tumour cells and they can therefore have severe side-effects (Chapter 21). 

Soy protein (i) Osteoporosis (ii) Breast and ovarian cancer (i) Presence of phyto-oestrogens which inhibit damage to DNA (ii) Phyto-oestrogens compete with oestrogen for receptors on breast and ovarian cells... 

The control of the levels of the sex hormones, oestrogen, progesterone and testosterone, is achieved by feedback inhibition of the secretions of both the pituitary and hypo-... 

Progestogens inhibit GnRH secretion and suppress LH release. They have anti-oestrogenic effects by reducing the number of oestrogen receptors and increasing oestradiol dehydrogenase. 

Jobling, S., D. Sheahan, J.A. Osborne, P. Matthiessen, and J.P. Sumpter. 1996. Inhibition of testicular growth in rainbow trout (Oncorhynchus mykiss) exposed to oestrogenic alkylphenolic chemicals. Environ. Toxicol. Chem. 15, 194-202. 

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