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      Effects of Dexamethasone and Dexamethasone plus Naltrexone on Pituitary Response to GnRH and TRH in Normal Women

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          The hypothesis that glucocorticoids have a direct central inhibitory effect on the reproductive axis is sutained by the identification of glucocorticoid receptors on GnRH-secreting neurons and gonadotropic pituitary cells. It has been proposed that glucocorticoids and opioids interact centrally in the regulation of the GnRH-LH axis. The inhibitory effect of glucocorticoids may manifest not only directly through the hormone-receptor link, but also indirectly through an increase in opioid tone. The aim of this study was to evaluate the role of glucocorticoids and glucocorticoids combined with an opioid antagonist, in the regulation of basal and GnRH- and TRH-stimulated secretion of LH, FSH and Prl in 7 women with normal menstrual cycles. Blood samples were obtained every 10 min for an hour. GnRH (50 μg) and TRH (200 μg) were administered and blood sampling was continued every 15 min for 2 h (day 1). At 5 a.m. the next day, naltrexone (50 mg) was given and at 8 a.m. the GnRH-TRH test was repeated (day 2). At 5 a.m. on day 3, the patients took 2 mg oral dexamethasone and the test was repeated. At 5 a.m. on day 4, the patients took naltrexone and dexamethasone and at 8 a.m. the GnRH-TRH test was repeated. Administration of naltrexone did not cause significant changes in basal concentrations of LH and FSH and their response to GnRH. The area under the curve of the LH response to GnRH on day 3 was significantly less than on days 1, 2 and 4. Administration of naltrexone (day 2) did not cause any significant increase in basal and TRH-stimulated levels of Prl with respect to day 1. On day 3, dexamethasone caused a reduced response of Prl to TRH. Pretreatment with naltrexone (day 4) prevented this reduction. These results suggest that suppression of the response of LH to GnRH induced by dexamethasone may be partly mediated by endogenous opioids. Dexamethasone led to a reduction in the response of Prl to TRH, and naltrexone blocked this suppression. Hence the suppression of Prl and LH by dexamethasone must be partly mediated by endogenous opioids, which must therefore inhibit pituitary secretion of Prl.

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          Most cited references 6

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          Central peptidergic neurons as targets for glucocorticoid action. Evidence for the presence of glucocorticoid receptor immunoreactivity in various types of classes of peptidergic neurons

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            Morphine- and opioid peptide-induced inhibition of the release of dopamine from tuberoinfundibular neurons

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              Glucocorticoid receptor colocalization with pituitary hormones in the rat pituitary gland


                Author and article information

                Horm Res Paediatr
                Hormone Research in Paediatrics
                S. Karger AG
                February 1999
                02 June 1999
                : 51
                : 2
                : 85-90
                Department of Obstetrics and Gynecology, University of Siena, Italy
                23320 Horm Res 1999;51:85–90
                © 1999 S. Karger AG, Basel

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                Page count
                Figures: 3, Tables: 1, References: 35, Pages: 6
                Original Paper


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