Rahim A, O'Neill P, Shalet S M
Department of Endocrinology, Christie Hospital, Manchester, UK.
Clin Endocrinol (Oxf). 1998 Nov;49(5):659-64. doi: 10.1046/j.1365-2265.1998.00586.x.
Growth hormone (GH) release is influenced by several factors including age, gender, physical exercise, nutritional status, sex steroids and body composition. The relationship with body composition is complex. Obesity is accompanied by suppression of spontaneous and stimulated GH release. As increasing body fat reduces stimulated GH secretion following a standard provocative test, the potential clinical uses of GH-releasing peptides (GHRPs), therapeutically or diagnostically, may be dependent on the relationship between body fat and GHRP-stimulated GH release. We have therefore assessed the effect of body composition and gender on the GH releasing capacity of hexarelin.
A single bolus of subcutaneous hexarelin at a dose of 1.5 micrograms per kg of body weight was administered at time 0. Blood samples were taken at -10, 0, 10, 20, 30, 40, 50, 60, 90, 120, 170 and 180 min.
Twenty-one (eight male) healthy elderly subjects with a median (range) age of 68 (60-81) years and BMI of 26 (19-30) kg/m2 were studied.
Dual-energy X-ray absorptiometry (DEXA) was used to assess body composition.
Peak GH response correlated negatively with fat mass, BMI, percentage body fat, and weight [r = -0.72, P = 0.0001; r = -0.56, P = 0.009; r = -0.63, P = 0.002 and r = -0.48, P = 0.029, respectively,]. AUC GH correlated negatively with fat mass, BMI and percentage fat mass [r = -0.58, P = 0.006; r = -0.51, P = 0.019 and r = -0.66, P = 0.001 respectively]. Using multiple linear regression, fat mass was the most useful predictor for both peak GH response [R2 = 0.61, P < 0.0001] and AUC GH [R2 = 0.38, P = 0.003]. Gender was not a significant variable.
Increasing total fat mass results in a blunted GH response following subcutaneous hexarelin. Total fat mass appears to be a useful predictor of peak GH response even in normal individuals as none of the subjects in the present study was morbidly obese. This indicates that there is a continuum of effect of fat mass on hexarelin-stimulated GH release. Any impact of gender on the GH response to hexarelin is almost certainly indirect and mediated via differences in body composition. This observation will have an impact on the potential diagnostic and therapeutic uses of hexarelin and related GH secretagogues.
生长激素（GH）的释放受多种因素影响，包括年龄、性别、体育锻炼、营养状况、性类固醇和身体成分。其与身体成分的关系较为复杂。肥胖伴随着自发性和刺激性GH释放的抑制。由于体脂增加会降低标准激发试验后刺激性GH的分泌，生长激素释放肽（GHRP）在治疗或诊断方面的潜在临床应用可能取决于体脂与GHRP刺激的GH释放之间的关系。因此，我们评估了身体成分和性别对六肽生长激素释放能力的影响。
在0时皮下注射单剂量六肽，剂量为每千克体重1.5微克。在-10、0、10、20、30、40、50、60、90、120、170和180分钟采集血样。
研究了21名（8名男性）健康老年受试者，年龄中位数（范围）为68（60 - 81）岁，体重指数（BMI）为26（19 - 30）kg/m²。
采用双能X线吸收法（DEXA）评估身体成分。
GH峰值反应与脂肪量、BMI、体脂百分比和体重呈负相关[r分别为-0.72，P = 0.0001；r = -0.56，P = 0.009；r = -0.63，P = 0.002；r = -0.48，P = 0.029]。GH曲线下面积（AUC GH）与脂肪量、BMI和脂肪量百分比呈负相关[r分别为-0.58，P = 0.006；r = -0.51，P = 0.019；r = -0.66，P = 0.001]。使用多元线性回归分析，脂肪量是GH峰值反应[R² = 0.61，P < 0.0001]和AUC GH[R² = 0.38，P = 0.003]最有用的预测指标。性别不是一个显著变量。
皮下注射六肽后，总脂肪量增加会导致GH反应减弱。即使在正常个体中，总脂肪量似乎也是GH峰值反应有用的预测指标，因为本研究中没有受试者是病态肥胖。这表明脂肪量对六肽刺激的GH释放存在连续的影响作用。性别对六肽GH反应的任何影响几乎肯定是间接的，并且是通过身体成分的差异介导的。这一观察结果将对六肽及相关GH促分泌素的潜在诊断和治疗应用产生影响。
