Discordant nadir GH after oral glucose and IGF-I levels on treated acromegaly: refining the biochemical markers of mild disease activity.
Biochemical markers for remission on acromegaly activity are controversial. We studied a subset of treated acromegalic patients with discordant nadir GH levels after oral glucose tolerance test (oGTT) and IGF-I values to refine the current consensus on acromegaly remission. We also compared GH results by two GH immunoassays. From a cohort of 75 treated acromegalic patients, we studied 13 patients who presented an elevated IGF-I despite post-oGTT nadir GH of < or =1 microg/l. The 12-h daytime GH profile (GH-12 h), nadir GH after oGTT, and basal IGF-I levels were studied in patients and controls. Bland-Altman method showed high concordance between GH assays. Acromegalic patients showed higher mean GH-12 h values (0.71+/-0.36 vs. 0.31+/-0.28 microg/l; p<0.05) and nadir GH after oGTT (0.48+/-0.32 vs. 0.097+/-0.002 microg/l; p<0.05) as compared to controls. Nadir GH correlated with mean GH-12 h (r=0.92, p<0.05). The mean GH-12 h value from upper 95% CI of controls (0.54 microg/l) would correspond to a theoretical normal nadir GH of < or =0.27 microg/l. Patients with GH nadir < or =0.3 microg/l had IGF-I between 100-130% ULNR (percentage of upper limit of normal range) and mean GH-12 h of 0.35+/-0.15, and patients with GH nadir >0.3 and < or =1 microg/l had IGF-I >130% ULNR and mean GH-12 h of 0.93+/-0.24 microg/l. Our data integrate daytime GH secretion, nadir GH after oGTT, and plasma IGF-I concentrations showing a continuum of mild residual activity in a subgroup of treated acromegaly with nadir GH values < or =1 microg/l. The degree of increased IGF-I levels and nadir GH after oGTT are correlated with the subtle abnormalities of daytime GH secretion.
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Division of Endocrinology and School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900 Ribeirão Preto, Brazil. lamparelli@hotmail.com
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D000172:Acromegaly / Q000378:metabolism* / Q000532:radiotherapy / Q000601:surgery; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D005947:Glucose / Q000378:metabolism; D005951:Glucose Tolerance Test; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged
D015415:Biomarkers; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D005947:Glucose