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Panminerva Medica 1998 June;40(2):98-102


lingua: Inglese

IGF-I levels in different conditions of low somatotrope secretion in adulthood: obesity in comparison with GH deficiency

Maccario M., Grottoli S., Aimaretti G., Gianotti L., Endrio Oleandri S., Procopio M., Savio P., Tassone F., Ramunni J., Camanni F., Ghigo E.

From the Department of Internal Medicine Division of Endocrinology, University of Turin, Turin, Italy


Background. 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.
Methods. To this goal, IGF-I lev­els were ­assayed after acid-eth­a­nol 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 µg/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±5.9 vs 171.3±4.8 µg/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 µg/l) were high­er (p<0.01) than those in GHD (64.5±5.9 µg/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 µg/l vs 224.0±9.2 µg/l).
Conclusions. 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.

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