Ramirez G, Herrera R, Pineda D, Bittle P A, Rabb H A, Bercu B B
Department of Internal Medicine, James A Haley VA Hospital, Tampa, Florida 33612, USA.
Clin Endocrinol (Oxf). 1995 Jul;43(1):11-8. doi: 10.1111/j.1365-2265.1995.tb01887.x.
Individuals adapted to high altitude (HA) have abnormalities in endocrine function and specifically in the pituitary-thyroid axis and aldosterone regulation. In this study we assessed hypothalamic-pituitary function in men adapted to high altitude living using exogenous administration of synthetic hypothalamic hormones.
Growth hormone releasing hormone (Geref 1-29) 1 microgram/kg, TRH 500 micrograms, GHRH 100 micrograms and ovine corticotrophin releasing hormone (oCRH) 1 microgram/kg were simultaneously administered intravenously to two groups of men: 12 born and raised in the city of Pasto, Colombia, South America, located at an altitude of 2600 m in the southern Colombian Andes (HA group) and 10 men living at sea level (SL) in Tampa, Florida.
The following hormones were measured: GH, IGF-I, TSH, T4, free T4, free T3, PRL, ACTH, beta-endorphin and cortisol. IGF binding protein-3 (IGFBP-3) and cortisol binding globulin (CBG) were also measured.
GH response to GHRH in HA men was exaggerated compared to SL men, and IGF-I concentration was also significantly increased in the presence of normal levels of IGFBP-3. No differences in TSH or PRL responses were found following TRH. HA men had lower basal total T4 levels, but higher free T4 and free T3 concentrations. The basal ACTH concentrations in the HA men were significantly lower than SL, although the response to oCRH was still present. beta-Endorphin basal levels were similar at HA and SL but the response to oCRH at HA was blunted. At HA, basal cortisol levels as well as CBG were elevated compared to SL and, in contrast to SL, did not increase significantly after endogenous ACTH secretion.
This study is the first description of exaggerated GH response to the administration of GHRH in HA men and also of a significant increase in IGF-I concentration in the same subjects in the presence of normal levels of IGFBP-3. An altered hypothalamic-pituitary response was found in HA men after administration of oCRH characterized by a significantly lower basal ACTH concentration at HA, although the response to oCRH was present but the beta-endorphin response to oCRH was blunted. At HA, basal cortisol levels, as well as CBG, were elevated and the cortisol levels did not significantly increase after endogenous ACTH secretion. We have characterized the differences in hypothalamic-pituitary dynamics after the administration of TRH, GnRH and oCRH in HA men comparing their response to age/sex matched SL men.
适应高海拔（HA）环境的个体存在内分泌功能异常，特别是垂体 - 甲状腺轴和醛固酮调节方面。在本研究中，我们通过外源性给予合成下丘脑激素来评估适应高海拔生活的男性的下丘脑 - 垂体功能。
将生长激素释放激素（Geref 1 - 29）1微克/千克、促甲状腺激素释放激素（TRH）500微克、生长激素释放激素（GHRH）100微克和羊促肾上腺皮质激素释放激素（oCRH）1微克/千克同时静脉注射给两组男性：12名出生并成长于南美洲哥伦比亚帕斯托市的男性，该市位于哥伦比亚南部安第斯山脉海拔2600米处（高海拔组），以及10名生活在佛罗里达州坦帕海平面（SL）的男性。
检测以下激素：生长激素（GH）、胰岛素样生长因子 - I（IGF - I）、促甲状腺激素（TSH）、甲状腺素（T4）、游离甲状腺素（free T4）、游离三碘甲状腺原氨酸（free T3）、催乳素（PRL）、促肾上腺皮质激素（ACTH）、β - 内啡肽和皮质醇。还检测了胰岛素样生长因子结合蛋白 - 3（IGFBP - 3）和皮质醇结合球蛋白（CBG）。
与海平面组男性相比，高海拔组男性对生长激素释放激素（GHRH）的生长激素（GH）反应增强，且在胰岛素样生长因子结合蛋白 - 3（IGFBP - 3）水平正常的情况下，胰岛素样生长因子 - I（IGF - I）浓度也显著升高。促甲状腺激素释放激素（TRH）注射后，促甲状腺激素（TSH）或催乳素（PRL）反应未发现差异。高海拔组男性基础总甲状腺素（T4）水平较低，但游离甲状腺素（free T4）和游离三碘甲状腺原氨酸（free T3）浓度较高。高海拔组男性基础促肾上腺皮质激素（ACTH）浓度显著低于海平面组，尽管对促肾上腺皮质激素释放激素（oCRH）仍有反应。高海拔组和海平面组β - 内啡肽基础水平相似，但高海拔组对促肾上腺皮质激素释放激素（oCRH）的反应减弱。在高海拔地区，基础皮质醇水平以及皮质醇结合球蛋白（CBG）均高于海平面组，且与海平面组不同，内源性促肾上腺皮质激素（ACTH）分泌后皮质醇水平未显著升高。
本研究首次描述了高海拔组男性对生长激素释放激素（GHRH）给药的生长激素（GH）反应增强，以及在胰岛素样生长因子结合蛋白 - 3（IGFBP - 3）水平正常的同一受试者中胰岛素样生长因子 - I（IGF - I）浓度显著增加。高海拔组男性在给予促肾上腺皮质激素释放激素（oCRH）后发现下丘脑 - 垂体反应改变，其特征为高海拔组基础促肾上腺皮质激素（ACTH）浓度显著降低，尽管对促肾上腺皮质激素释放激素（oCRH）仍有反应，但β - 内啡肽对促肾上腺皮质激素释放激素（oCRH）的反应减弱。在高海拔地区，基础皮质醇水平以及皮质醇结合球蛋白（CBG）均升高，内源性促肾上腺皮质激素（ACTH）分泌后皮质醇水平未显著增加。我们比较了高海拔组男性与年龄/性别匹配的海平面组男性在给予促甲状腺激素释放激素（TRH）、促性腺激素释放激素（GnRH）和促肾上腺皮质激素释放激素（oCRH）后下丘脑 - 垂体动力学的差异。
