الفهرس 
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Abstract
Numerous studies have suggested that estrogen replacement therapy could improve insulin sensitivity in postmenopausal women. While others reported that estrogen replacement therapy either worsens insulin action or has no effect on insulin action. So this research aimed to study the effect of 17<U+00DF> estradiol in modulating insulin action as manifested by measuring changes in insulin resistance at different phases of simulated levels of 17<U+00DF> estradiol found in normal pregnancy and at pharmacological doses of this hormone in ovarectomized nonpregnant female rats. In group I: rats were non ovarectomized non medically treated. They were subdivided into 3 subgroups according to day of sampling. Rats in groups II, III and IV were surgically ovarectomized and allowed 3 days to recover from stress of surgery and for hormonal levels to decrease. Then animals were injected subcutaneously every 12 hours with 17 beta estradiol in sesame oil suspension (group III and IV) or with sesame oil only (vehicle) (group II). from our results, we conclude that surgical ovarectomy in rats, leads to significant insulin resistance as compared with nonovarectomized animals. In the simulated pregnancy experiment insulin resistance was significantly higher in the late stage compared with the other two stages. The administration of gestational doses of 17beta estradiol seems, therefore, to be responsible for the changes in insulin action seen in normal pregnancy. The use of high doses of 17beta estradiol, on the other hand, induced significant increase in insulin resistance than ovarectomized rats and those which received low doses (simulated pregnancy). So we can conclude that the effect of estrogen on insulin action in dose dependant.