Carretti N, Florio P, Reis F M, Comai S, Petraglia F, Costa C V L
Department of Pediatrics, Obstetrics and Reproductive Medicine, University of Siena, Siena, Italy.
Climacteric. 2007 Oct;10(5):393-9. doi: 10.1080/13697130701378198.
Tryptophan, the serotonin (5-HT) precursor, is circulating in blood in both free (FT) and protein-bound forms. The free form crosses the hematoencephalic barrier and is converted into 5-HT. During the fertile years, tryptophan levels are negatively correlated to gonadotropin concentrations. The present study aims to evaluate the correlation between circulating tryptophan, gonadotropin and estradiol (E2) levels postmenopause.
Serum levels of total tryptophan (TT, free + protein-bound) and FT, and plasma luteinizing hormone (LH), follicle stimulating hormone (FSH), and E2 were determined in 15 postmenopausal women and 15 cycling women during follicular (days 7-10), periovulatory (days 13-16) and luteal (days 21-24) phases of the menstrual cycle. Data were analyzed by ANOVA, linear correlation coefficients and hierarchical cluster analysis of variables.
TT, but not FT, levels were significantly (p<0.05) higher in postmenopausal (12.07+/-0.40 microg/ml) than fertile women in the periovulatory period (10.46+/-0.36 microg/ml). In postmenopausal women, there was no significant correlation between TT and FT, nor between these tryptophan forms and gonadotropins, but only between FT and E2. Cluster analysis showed that the main cluster composed by FSH-LH-TT-FT observed in fertile women was absent in postmenopause, since both serum tryptophan forms were distant from gonadotropins.
High TT levels circulate in postmenopausal women, with lack of correlation between TT and FT, and FT/TT and gonadotropins. Since estrogens play a pivotal role on central 5-HT metabolism, estrogen deprivation may alter the brain tryptophan utilization for 5-HT synthesis and its relation to gonadotropin release.
色氨酸是血清素（5-羟色胺，5-HT）的前体，以游离（FT）和蛋白结合两种形式在血液中循环。游离形式穿过血脑屏障并转化为5-羟色胺。在生育期，色氨酸水平与促性腺激素浓度呈负相关。本研究旨在评估绝经后循环色氨酸、促性腺激素和雌二醇（E2）水平之间的相关性。
测定了15名绝经后女性以及15名处于月经周期卵泡期（第7 - 10天）、排卵期（第13 - 16天）和黄体期（第21 - 24天）的育龄期女性血清中的总色氨酸（TT，游离 + 蛋白结合）和FT水平，以及血浆促黄体生成素（LH）、促卵泡激素（FSH）和E2水平。通过方差分析、线性相关系数和变量的层次聚类分析对数据进行分析。
绝经后女性（12.07±0.40微克/毫升）的TT水平显著高于排卵期育龄期女性（10.46±0.36微克/毫升）（p<0.05），而FT水平无显著差异。在绝经后女性中，TT与FT之间、这些色氨酸形式与促性腺激素之间均无显著相关性，但FT与E2之间存在显著相关性。聚类分析表明，在绝经后不存在生育期女性中由FSH - LH - TT - FT组成的主要聚类，因为两种血清色氨酸形式均与促性腺激素距离较远。
绝经后女性循环中TT水平较高，TT与FT之间以及FT/TT与促性腺激素之间缺乏相关性。由于雌激素在中枢5-羟色胺代谢中起关键作用，雌激素缺乏可能会改变大脑色氨酸用于5-羟色胺合成的利用率及其与促性腺激素释放的关系。
