Aimaretti G, Colao A, Corneli G, Pivonello R, MacCario M, Morrison K, Pflaum C D, Strasburger C J, Lombardi G, Ghigo E
Division of Endocrinology, Department of Internal Medicine, University of Turin, Italy.
Clin Endocrinol (Oxf). 1999 Dec;51(6):771-7. doi: 10.1046/j.1365-2265.1999.00885.x.
Within an appropriate clinical context, GH deficiency (GHD) in adults can only be diagnosed biochemically by provocative testing. The evaluation of IGF-I, IGFBP-3 and even of spontaneous GH secretion do not establish the diagnosis of adult GHD. In fact, remarkable overlaps between normal and GHD adults have been reported for all these parameters. On the other hand, it is well known that even short-term fasting stimulates GH secretion in normal subjects. The aim of our study was to determine the effects of 36 h fasting on 8-h diurnal GH, insulin and glucose levels as well as on basal IGF-I, IGFBP-3, acid-labile subunit (ALS), IGFBP-1, GHBP and free fatty acid (FFA) levels.
We studied 9 GHD adults (GHD, 8 males, 1 female; age, mean +/- SEM: 37.6 +/- 2.3 years, body mass index (BMI): 24.5 +/- 1.0 kg/m2) and 20 age-matched normal subjects (NS) as controls (13 males, 7 females; age: 28.9 +/- 0.6 years, BMI: 21.6 +/- 0.4 kg/m2).
In all subjects we studied the effects of 36 h fasting on 8-h daytime GH, insulin and glucose levels (assay every 30 min from 0800 h to 1600 h) as well as on basal IGF-I, IGFBP-3, ALS, IGFBP-1, GHBP and FFA levels.
Before fasting, basal mean IGF-I, IGFBP-3 and ALS levels in GHD were lower (P < 0. 0001) than in NS. IGFBP-1, GHBP and FFA levels were similar in both groups. Before fasting mean GH concentration (mGHc) in GHD was lower (P < 0.05) than in NS (0.4 +/- 0.2 vs. 2.2 +/- 0.6 mu/l) but with a clear overlap between the 2 groups (range 0.4-0.8 vs. 0.4-6.8 mu/l). After fasting, both in GHD and NS basal IGF-I, IGFBP-3, ALS and GHBP levels did not change significantly. On the other hand, in both GHD and in NS IGFBP-1 was increased (P < 0.0001) to a similar extent, while FFA increased in NS more (P < 0.01) than in GHD. Fasting significantly increased mGHc in NS (12.0 +/- 1.2 mu/l, P < 0.0001) but not in GHD (0.6 +/- 0.2 mu/l). After fasting, no overlap was present between GHD and NS (0.4-1.6 vs. 2.4-20.8 mu/l, respectively). Mean glucose and insulin concentrations over 8 h in GHD and NS in basal conditions were similar and were reduced to the same extent in both groups.
Our findings demonstrate that after short-term fasting, the study of spontaneous GH secretion distinguishes between GH-deficient adults and normal subjects; this phenomenon occurs before significant changes in IGF-I and IGFBP-3 levels. These results suggest that the assessment of spontaneous GH secretion could be useful for the diagnosis of adult GH deficiency only after short-term fasting.
在适当的临床背景下，成人生长激素缺乏症（GHD）只能通过激发试验进行生化诊断。对胰岛素样生长因子-I（IGF-I）、胰岛素样生长因子结合蛋白-3（IGFBP-3）甚至自发性生长激素分泌的评估并不能确诊成人GHD。事实上，已有报道称，所有这些参数在正常成人和GHD成人之间存在显著重叠。另一方面，众所周知，即使短期禁食也会刺激正常受试者的生长激素分泌。我们研究的目的是确定36小时禁食对8小时日间生长激素、胰岛素和葡萄糖水平以及基础IGF-I、IGFBP-3、酸性不稳定亚基（ALS）、IGFBP-1、生长激素结合蛋白（GHBP）和游离脂肪酸（FFA）水平的影响。
我们研究了9名GHD成人（GHD组，8名男性，1名女性；年龄，平均±标准误：37.6±2.3岁，体重指数（BMI）：24.5±1.0kg/m²）和20名年龄匹配的正常受试者（NS组）作为对照（13名男性，7名女性；年龄：28.9±0.6岁，BMI：21.6±0.4kg/m²）。
在所有受试者中，我们研究了36小时禁食对8小时日间生长激素、胰岛素和葡萄糖水平（从08:00至16:00每30分钟检测一次）以及基础IGF-I、IGFBP-3、ALS、IGFBP-1、GHBP和FFA水平的影响。
禁食前，GHD组的基础平均IGF-I、IGFBP-3和ALS水平低于NS组（P<0.0001）。两组的IGFBP-1、GHBP和FFA水平相似。禁食前，GHD组的平均生长激素浓度（mGHc）低于NS组（P<0.05）（0.4±0.2 vs. 2.2±0.6μ/l），但两组之间有明显重叠（范围0.4 - 0.8 vs. 0.4 - 6.8μ/l）。禁食后，GHD组和NS组的基础IGF-I、IGFBP-3、ALS和GHBP水平均无显著变化。另一方面，GHD组和NS组的IGFBP-1均有相似程度的升高（P<0.0001），而NS组的FFA升高幅度大于GHD组（P<0.01）。禁食显著增加了NS组的mGHc（12.0±1.2μ/l，P<0.0001），但未增加GHD组的mGHc（0.6±0.2μ/l）。禁食后，GHD组和NS组之间无重叠（分别为0.4 - 1.6 vs. 2.4 - 20.8μ/l）。基础状态下GHD组和NS组8小时内的平均葡萄糖和胰岛素浓度相似，且两组均降低到相同程度。
我们的研究结果表明，短期禁食后，对自发性生长激素分泌的研究可区分生长激素缺乏的成人和正常受试者；这种现象发生在IGF-I和IGFBP-3水平出现显著变化之前。这些结果表明，仅在短期禁食后，评估自发性生长激素分泌可能有助于诊断成人生长激素缺乏症。
