Maccario M, Grottoli S, Aimaretti G, Gianotti L, Endrio Oleandri S, Procopio M, Savio P, Tassone F, Ramunni J, Camanni F, Ghigo E
Department of Internal Medicine, University of Turin, Italy.
Panminerva Med. 1998 Jun;40(2):98-102.
It is widely accepted that IGF-I synthesis and release depend on GH secretion as well as on the nutritional status and vary with age. Based on these premises, after the definition of normal IGF-I levels during lifespan, in a large population of normal subjects of both sexes, our aim was to verify IGF-I levels in large groups of adult patients with GH deficiency or obesity, a condition in which a reduced somatotrope secretion is well known.
To this goal, IGF-I levels were assayed after acidethanol extraction, in 326 normal subjects (NS, 98 men and 228 women, age 20-80 yrs, BMI 17.9-26.1 kg/m2), 54 patients with GH deficiency (GHD), 24 men and 30 women, age 20-80 yrs, BMI 18.2-27.1 kg/m2), and 195 patients with obesity (OB, 33 men and 162 women, age 17-71 yrs, BMI 27.7-64.9 kg/m2). In NS, IGF-I levels were similar in both sexes and showed a progressive decrease with age. No correlation was present between IGF-I and BMI in NS. Median IGF-I levels and the 3rd centile in NS when considered per decade were: III) 230 and 108.6; IV) 220 and 129.8; V) 150.5 and 72.4; VI) 163.0 and 62.4; VII) 110 and 41.6; VIII) 82 and 24.7 microgram/l. In GHD, IGF-I levels were independent on sex and did not show reduction during lifespan. Mean IGF-I levels in GHD were lower than that in NS (64 +/- 5.9 vs 171.3 +/- 4.8 microgram/l, p < 0.01) and did not correlate with age or BMI. Analyzing individual IGF-I levels, in GHD, in the III and IV decade 21/24 patients had IGF-I levels lower than 3rd centile while, up to the VIII decade, only 10/30 had IGF-I levels below normal limits. In OB, IGF-I levels were independent on sex but, like in NS, showed a progressive decrease with age and were independently, negatively correlated with BMI but not with WHR. Analyzing individual IGF-I levels, in OB, IGF-I levels were below 3rd centile in 10/77 patients in the III and IV decade and in only 8/108 patients up to the VIII decade. Mean IGF-I levels in the whole OB population (179.6 +/- 5.9 microgram/l) were higher (p < 0.01) than those in GHD (64.5 +/- 5.9 microgram/l) while only in the IV decade IGF-I levels in OB group were lower (p < 0.02) than those in NS (184.7 +/- 12.6 microgram/l vs 224.0 +/- 9.2 microgram/l).
In conclusion, present data confirm that IGF-I levels depends on GH secretion as well as on nutritional status, being negatively and independently correlated with age and BMI. IGF-I assay is not a reliable test for the diagnosis of GH deficiency in adulthood though it gives good discrimination between GHD and normal subjects up to 40 yrs of age. In spite of low GH secretion, IGF-I levels are only slightly reduced in obesity, probably as consequence of hyperinsulinism.
普遍认为，胰岛素样生长因子-I（IGF-I）的合成与释放取决于生长激素（GH）的分泌以及营养状况，并且会随年龄变化。基于这些前提，在确定了不同年龄段正常IGF-I水平后，我们的目标是在一大群正常男女受试者中，验证大量成年生长激素缺乏症患者或肥胖症患者的IGF-I水平，肥胖症是一种已知生长激素分泌减少的病症。
为实现这一目标，对326名正常受试者（NS，98名男性和228名女性，年龄20 - 80岁，体重指数17.9 - 26.1kg/m²）、54名生长激素缺乏症（GHD）患者（24名男性和30名女性，年龄20 - 80岁，体重指数18.2 - 27.1kg/m²）以及195名肥胖症（OB）患者（33名男性和162名女性，年龄17 - 71岁，体重指数27.7 - 64.9kg/m²）进行了酸乙醇提取后IGF-I水平的检测。在正常受试者中，IGF-I水平在两性中相似，且随年龄逐渐降低。正常受试者中IGF-I与体重指数之间无相关性。按每十年考虑，正常受试者中IGF-I水平的中位数及第三百分位数为：III）230和108.6；IV）220和129.8；V）150.5和72.4；VI）163.0和62.4；VII）110和41.6；VIII）82和24.7微克/升。在生长激素缺乏症患者中，IGF-I水平与性别无关，且在整个生命周期中未显示降低。生长激素缺乏症患者的平均IGF-I水平低于正常受试者（64±5.9对171.3±4.8微克/升，p<0.01），且与年龄或体重指数无关。分析生长激素缺乏症患者个体的IGF-I水平，在第三和第四个十年中，21/24名患者的IGF-I水平低于第三百分位数，而直到第八个十年，只有10/30名患者的IGF-I水平低于正常范围。在肥胖症患者中，IGF-I水平与性别无关，但与正常受试者一样，随年龄逐渐降低，且与体重指数呈独立负相关，但与腰臀比无关。分析肥胖症患者个体的IGF-I水平，在第三和第四个十年中，10/77名患者的IGF-I水平低于第三百分位数，直到第八个十年只有8/108名患者。肥胖症患者总体的平均IGF-I水平（179.6±5.9微克/升）高于生长激素缺乏症患者（64.5±5.9微克/升，p<0.01），而仅在第四个十年中，肥胖症组的IGF-I水平低于正常受试者（184.7±12.6微克/升对224.0±9.2微克/升，p<0.02）。
总之，目前的数据证实IGF-I水平取决于生长激素分泌以及营养状况，与年龄和体重指数呈负相关且相互独立。IGF-I检测对于成年期生长激素缺乏症的诊断并非可靠的检测方法，尽管在40岁之前它能很好地区分生长激素缺乏症患者和正常受试者。尽管生长激素分泌减少，但肥胖症患者的IGF-I水平仅略有降低，可能是高胰岛素血症的结果。
