Rosário Pedro W S, Furtado Mariana S
Laboratório ANALYSA, Belo Horizonte, MG, Brasil.
Arq Bras Endocrinol Metabol. 2008 Oct;52(7):1139-44. doi: 10.1590/s0004-27302008000700010.
The evaluation of growth hormone (GH) secretion continues to be important in acromegaly and the nadir GH (n-GH) level in the oral glucose tolerance test (OGTT) is the gold standard for the demonstration of secretory autonomy of this hormone. n-GH levels < 1 microg/L are defined as normal suppression but, using current assays, n-GH < 1 microg/L is detected in patients with untreated acromegaly and this value seems to be much lower in normal subjects. The objective of the present study was to evaluate n-GH levels in the OGTT in normal subjects using three different assays (GH ICMA Immulite; GH IRMA DSL and GH IFMA AutoDelfia). Two-hundred apparently healthy subjects (120 women) ranging in age from 18 to 70 years and with a BMI > 18.5 and < 27 kg/m(2), who used no medications and presented normal glycemia, blood count, albumin, creatinine, TSH, SGOT, SGPT and bilirubin were studied. Serum samples were obtained before and 30,60,90 and 120 min after oral administration of 75 g glucose. The test was repeated after 4 weeks in 157 participants, with the same protocol being used in 79 and 78 receiving an overload of 100 g glucose. n-GH cut-off values (97.5th percentile) were higher in women than in men (GH-IFMA: 0.30 versus 0.11 microg/L; GH-ICMA: 0.60 versus 0.25 microg/L; GH-IRMA: 0.20 versus 0.10 microg/L, respectively). No correlation was observed between n-GH and age or BMI. A difference was only observed when comparing women < 35 years (n = 40) versus > 35 years (n = 80), with higher values in the former (n-GH cut-off in this subgroup: GH-IFMA 0.40 versus 0.26 microg/L, GH-ICMA 0.74 versus 0.50 microg/L, GH-IRMA 0.25 versus 0.15 microg/L). A good correlation was observed between the assays (r = 0.9-0.96), however, the highest values were always obtained with the Immulite assay. Test repetition with 75 g oral glucose showed a variation in n-GH < 10.2% (GH-IFMA), < 13.4% (GH-ICMA) and < 11% (GH-IRMA) in 95% of the subjects. This variation was similar when the test was repeated with 100 g glucose. A good correlation was observed between n-GH in the first and second test (r = 0.83-0.92). We suggest the following n-GH reference values: for men, 0.14 microg/L for the GH IRMA DSL and GH IFMA AutoDelfia kits and 0.25 microg/L for the GH ICMA Immulite kit; for women, 0.25 microg/L, 0.40 microg/L and 0.70 microg/L, respectively.
生长激素（GH）分泌的评估在肢端肥大症中仍然很重要，口服葡萄糖耐量试验（OGTT）中的最低GH（n-GH）水平是证明该激素分泌自主性的金标准。n-GH水平<1μg/L被定义为正常抑制，但使用当前检测方法，在未经治疗的肢端肥大症患者中可检测到n-GH<1μg/L，而在正常受试者中该值似乎要低得多。本研究的目的是使用三种不同检测方法（GH ICMA Immulite；GH IRMA DSL和GH IFMA AutoDelfia）评估正常受试者OGTT中的n-GH水平。研究了200名年龄在18至70岁之间、BMI>18.5且<27kg/m²、未使用药物且血糖、血常规、白蛋白、肌酐、促甲状腺激素、谷草转氨酶、谷丙转氨酶和胆红素正常的明显健康受试者（120名女性）。在口服75g葡萄糖之前以及之后30、60、90和120分钟采集血清样本。157名参与者在4周后重复该试验，79名和78名分别接受100g葡萄糖负荷，采用相同方案。女性的n-GH临界值（第97.5百分位数）高于男性（GH-IFMA：0.30对0.11μg/L；GH-ICMA：0.60对0.25μg/L；GH-IRMA：0.20对0.10μg/L）。未观察到n-GH与年龄或BMI之间的相关性。仅在比较<35岁（n = 40）与>35岁（n = 80）的女性时观察到差异，前者的值更高（该亚组中的n-GH临界值：GH-IFMA为0.40对0.26μg/L，GH-ICMA为0.74对0.50μg/L，GH-IRMA为0.25对0.15μg/L）。各检测方法之间观察到良好的相关性（r = 0.9 - 0.96），然而，Immulite检测方法始终获得最高值。95%的受试者口服75g葡萄糖重复试验时，n-GH的变化<10.2%（GH-IFMA）、<13.4%（GH-ICMA）和<11%（GH-IRMA）。用100g葡萄糖重复试验时，这种变化相似。首次和第二次试验的n-GH之间观察到良好的相关性（r = 0.83 - 0.92）。我们建议以下n-GH参考值：对于男性，GH IRMA DSL和GH IFMA AutoDelfia试剂盒为0.14μg/L，GH ICMA Immulite试剂盒为0.25μg/L；对于女性，分别为0.25μg/L、0.40μg/L和0.70μg/L。
