BACKGROUND & AIMS:
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 microg/d for the first week, 50 microg/d the second week, 25 microg/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.
背景与目标:
背景:雌二醇通过下丘脑和垂体的作用抑制男性促性腺激素的释放。由于芳香酶的组织特异性调节,外周雌二醇水平可能无法反映脑中雌二醇的浓度。
目的:我们评估了下丘脑或垂体中睾丸激素的局部芳香化对促性腺激素的释放是否重要,以及循环雌激素在多大程度上影响促性腺激素水平和外周睾丸激素水平。设计,受试者和干预措施:我们每天用一次来曲唑2.5 mg抑制10名年轻健康男性的芳香化酶活性,用雌二醇贴片恢复血浆雌二醇水平(第一周为100微克/天,第二周为50微克/天,第二周为25微克在第3周/ d,并且在第4周没有雌二醇贴片),并测量血浆睾丸激素,雌二醇,LH,FSH和SHBG的水平。
结果:研究期间的平均雌二醇和睾丸激素水平范围为:雌二醇为68.6 /-38.3至12.6 /-7.21 pg / ml,睾丸激素为179 /-91和955 /-292 ng / dl(平均值/-sd)。睾丸激素,LH和FSH的水平与外周雌二醇水平成反比。在使用来曲唑的过程中,将睾丸激素,LH和FSH水平恢复到基线水平所需的平均血浆雌二醇水平与基线平均雌二醇水平没有显着差异。
结论:下丘脑-垂体区室中睾丸激素的局部芳香化不是表达雌激素对男性促性腺激素分泌抑制作用的先决条件。周围雌二醇水平直接反映了雌激素对促性腺激素释放的抑制作用,并且是周围睾丸激素,LH和FSH水平的主要决定因素。