Kelestimur Fahrettin, Popovic Vera, Leal Alfonso, Van Dam P Sytze, Torres Elena, Perez Mendez Luisa F, Greenman Yona, Koppeschaar Hans P F, Dieguez Carlos, Casanueva Felipe F
Department of Endocrinology, Erciyes University, Kayseri, Turkey.
Clin Endocrinol (Oxf). 2006 Jun;64(6):667-71. doi: 10.1111/j.1365-2265.2006.02525.x.
Obesity is characterized by low basal levels of growth hormone (GH) and impeded GH release. However, the main problem arises in the diagnosis of GH deficiency in adults, as all accepted cut-offs in the diagnostic tests of GH reserve are no longer valid in obese subjects. In this work, the role of obesity in the GH response elicited by the GHRH + GHRP-6 test was assessed in a large population of obese and nonobese subjects.
GHRH + GHRP-6-induced GH peaks were evaluated in 542 subjects. One hundred and five were healthy obese, 50 were morbid obese, and 261 were nonobese (both normal weight and overweight). One hundred and seventy-six GH-deficient patients (obese and nonobese) were also studied.
A regression analysis of the 366 subjects with normal pituitary function indicated that adiposity had a negative effect on the elicited GH peak (r = -0.503, P < 0.0001). A receiver operating characteristic (ROC) curve analysis showed that in subjects with a BMI < or =35, the currently accepted cut-offs of the GHRH + GHRP-6 test (GH peaks > or =20 microg/l: normal secretion; GH peaks < or =10 microg/l: GH deficiency), were fully operative. However, in subjects with a BMI > 35, normality was indicated by GH peaks > or =15 microg/l and GH deficiency by peaks < or =5 microg/l (1 microg/l = 2.6 mU/l).
This study confirms: (a) that the combined provocative test is adequate to separate normal and GH-deficient subjects; (b) the negative effect of obesity on GH secretion; (c) that obesity accounts for 25% of the reduction of GH release; and (d) that present cut-off values are applicable to normal weight, overweight and grade I obesity subjects, whereas in obese subjects with a BMI exceeding 35, all the normative limits of the GHRH-GHRP +6 test must be reduced by 5 microg/l.
肥胖的特征是生长激素（GH）基础水平低且GH释放受阻。然而，成人GH缺乏症的诊断存在主要问题，因为GH储备诊断测试中所有公认的临界值在肥胖受试者中不再有效。在这项研究中，在大量肥胖和非肥胖受试者中评估了肥胖在GHRH + GHRP - 6试验引发的GH反应中的作用。
对542名受试者评估了GHRH + GHRP - 6诱导的GH峰值。其中105名是健康肥胖者，50名是病态肥胖者，261名是非肥胖者（包括正常体重和超重者）。还研究了176名GH缺乏患者（肥胖和非肥胖）。
对366名垂体功能正常的受试者进行回归分析表明，肥胖对引发的GH峰值有负面影响（r = -0.503，P < 0.0001）。受试者工作特征（ROC）曲线分析表明，在BMI≤35的受试者中，目前公认的GHRH + GHRP - 6试验临界值（GH峰值≥20μg/L：正常分泌；GH峰值≤10μg/L：GH缺乏）完全适用。然而，在BMI> 35的受试者中，GH峰值≥15μg/L表明正常，峰值≤5μg/L表明GH缺乏（1μg/L = 2.6 mU/L）。
本研究证实：（a）联合激发试验足以区分正常和GH缺乏受试者；（b）肥胖对GH分泌有负面影响；（c）肥胖占GH释放减少的25%；（d）目前的临界值适用于正常体重、超重和I级肥胖受试者，而在BMI超过35的肥胖受试者中，GHRH - GHRP +6试验的所有正常范围界限必须降低5μg/L。
