Acromegalia: comparación de los niveles séricos de IGF-I por dos inmunoensayos y su correlación con la prueba de tolerancia oral a la glucosa

introduction: igf-i determination in serum or plasma is an essential tool in the diagnosis and follow-up of acromegaly. hepatic production of igf-i is regulated by gh and circulates bound to several igf-i binding proteins which extends its half life. igf-i is not released in a pulsatile pattern and has no significant variability in 24 h. objective: to evaluate two different methodologies in igf-i levels determination and their correlation with gh nadir in ogtt in acromegalic patients. material and methods: we analyzed 37 acromegalic patients, 20 women and 17 men, mean age was 45±12 years. igf-i levels were assayed by immulite 1000, dpc (imm) and dsl-5600 active？ igf-i coated-tube irma (dsl) and ogtts (at baseline and at 30, 60, 90 and 120 minutes) were performed by measuring plasma glucose and gh assay by immunochemiluminometric assay (access); we considered a nadir <1ng/ml as normal response. nine patients were under medical treatment (cabergoline: 4, octeotride: 4, and cabergoline plus octeotrite: 1) and 28 without treatment. statistical analysis: wilcoxon and, bland and altman tests and roc curves. differences were considered significant at p< 0.05. results: basal glucose levels were 97.86±10.91 mg/dl and mean gh was 2.8 (1.59-14.4) ng/ml. mean igf-i levels performed by imm were 602±318 ng/ml and 1006±596 ng/ml by dsl. there was a statistically significant difference between both methodologies (p<0.01). bland and altman test showed a bias of - 403.2 ng/ml with lower values by imm. we observed elevated igf-i levels in 84% by imm and in 97% by dsl, and only one patient had normal levels with both methodologies. elevated igf-i levels and gh nadir >1ng/ml were observed in 70% of the patients, increased igf-i with normal gh nadir in 13.5%, normal igf-i with gh nadir >1ng/ml in 2.7% and normal igf-i with normal gh nadir in 13.5%. patients under treatment: 3 showed normal gh nadir with elevated igf-i levels, in 2 of them by both methodologies, and in the other one it wa