In Men, Peripheral Estradiol Levels Directly Reflect the Action of Estrogens at the Hypothalamo-Pituitary Level to Inhibit Gonadotropin Secretion Export

@article{citeulike:2833448, abstract = {Context: Estradiol inhibits gonadotropin release in men by an action at the hypothalamus and pituitary. Because of the tissue-specific regulation of aromatase, peripheral estradiol levels may not reflect brain estradiol concentrations. Objective: We evaluated whether local aromatization of testosterone in the hypothalamus or pituitary is important for gonadotropin release and to what extent circulating estrogens affect gonadotropin levels and peripheral testosterone levels. Design, Subjects, and Interventions: We suppressed aromatase activity in 10 young healthy men with letrozole 2.5 mg once daily, restored plasma estradiol levels with estradiol patches (100 {micro}g/d for the first week, 50 {micro}g/d the second week, 25 {micro}g/d the third week, and no estradiol patch the fourth week) and measured plasma testosterone, estradiol, LH, FSH, and SHBG levels. Results: The mean estradiol and testosterone levels during the study ranged between 68.6 {+/-} 38.3 and 12.6 {+/-} 7.21 pg/ml for estradiol and 179 {+/-} 91 and 955 {+/-} 292 ng/dl (mean {+/-} SD) for testosterone. Levels of testosterone, LH, and FSH were inversely related to peripheral estradiol levels. During letrozole use, the mean plasma estradiol level needed to restore testosterone, LH, and FSH levels to baseline levels was not significantly different from the baseline mean estradiol level. Conclusions: Local aromatization of testosterone in the hypothalamo-pituitary compartment is not a prerequisite for expression of the inhibitory action of estrogens on gonadotropin secretion in men. Peripheral estradiol levels directly reflect the inhibitory tone exerted by estrogens on gonadotropin release and are a major determinant of peripheral testosterone, LH, and FSH levels. 10.1210/jc.2006-0462}, author = {Raven, Garrett and de Jong, Frank H. and Kaufman, Jean-Marc and de Ronde, Willem}, citeulike-article-id = {2833448}, citeulike-linkout-0 = {http://dx.doi.org/10.1210/jc.2006-0462}, citeulike-linkout-1 = {http://jcem.endojournals.org/cgi/content/abstract/91/9/3324}, citeulike-linkout-2 = {http://view.ncbi.nlm.nih.gov/pubmed/16787981}, citeulike-linkout-3 = {http://www.hubmed.org/display.cgi?uids=16787981}, day = {1}, doi = {10.1210/jc.2006-0462}, journal = {J Clin Endocrinol Metab}, keywords = {aromatase, estradiol, estrogen, inhibitor, reference}, month = {September}, number = {9}, pages = {3324--3328}, posted-at = {2008-05-26 11:16:56}, priority = {2}, title = {In Men, Peripheral Estradiol Levels Directly Reflect the Action of Estrogens at the Hypothalamo-Pituitary Level to Inhibit Gonadotropin Secretion}, url = {http://dx.doi.org/10.1210/jc.2006-0462}, volume = {91}, year = {2006} }

TY - JOUR ID - citeulike:2833448 L3 - citeulike-article-id:2833448 N2 - Context: Estradiol inhibits gonadotropin release in men by an action at the hypothalamus and pituitary. Because of the tissue-specific regulation of aromatase, peripheral estradiol levels may not reflect brain estradiol concentrations. Objective: We evaluated whether local aromatization of testosterone in the hypothalamus or pituitary is important for gonadotropin release and to what extent circulating estrogens affect gonadotropin levels and peripheral testosterone levels. Design, Subjects, and Interventions: We suppressed aromatase activity in 10 young healthy men with letrozole 2.5 mg once daily, restored plasma estradiol levels with estradiol patches (100 {micro}g/d for the first week, 50 {micro}g/d the second week, 25 {micro}g/d the third week, and no estradiol patch the fourth week) and measured plasma testosterone, estradiol, LH, FSH, and SHBG levels. Results: The mean estradiol and testosterone levels during the study ranged between 68.6 {+/-} 38.3 and 12.6 {+/-} 7.21 pg/ml for estradiol and 179 {+/-} 91 and 955 {+/-} 292 ng/dl (mean {+/-} SD) for testosterone. Levels of testosterone, LH, and FSH were inversely related to peripheral estradiol levels. During letrozole use, the mean plasma estradiol level needed to restore testosterone, LH, and FSH levels to baseline levels was not significantly different from the baseline mean estradiol level. Conclusions: Local aromatization of testosterone in the hypothalamo-pituitary compartment is not a prerequisite for expression of the inhibitory action of estrogens on gonadotropin secretion in men. Peripheral estradiol levels directly reflect the inhibitory tone exerted by estrogens on gonadotropin release and are a major determinant of peripheral testosterone, LH, and FSH levels. 10.1210/jc.2006-0462 IS - 9 JF - J Clin Endocrinol Metab EP - 3328 TI - In Men, Peripheral Estradiol Levels Directly Reflect the Action of Estrogens at the Hypothalamo-Pituitary Level to Inhibit Gonadotropin Secretion VL - 91 SP - 3324 KW - aromatase KW - estradiol KW - estrogen KW - inhibitor KW - reference AU - Raven, Garrett AU - de Jong, Frank AU - Kaufman, Jean-Marc AU - de Ronde, Willem PY - 2006/09/01/ UR - http://dx.doi.org/10.1210/jc.2006-0462 ER -