Discordant Nadir GH After Oral Glucose and IGF-I Levels on Treated Acromegaly: Refining the Biochemical Markers of Mild Disease Activity

Author(s)

Elias, P. C. L. ^[1] ; Lugao, H. B. ^[2] ; Pereira, M. C. ^[2] ; Machado, H. R. ^[2] ; de Castro, M. ^[2] ; Moreira, A. C. ^[2]

Affiliation

^[1] Univ Sao Paulo, Sch Med Ribeirao Preto, Dept Med, Div Neurosurg, BR-14049900 Ribeirao Preto - Brazil

^[2] Univ Sao Paulo, Div Endocrinol, BR-14049900 Ribeirao Preto - Brazil

• Document type: Journal article
• Source: Hormone and Metabolic Research; v. 42, n. 1, p. 50-55, JAN 2010.
• Web of Science Citations: 20

Abstract

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 <= 1 mu g/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 mu g/l; p<0.05) and nadir GH after oGTT (0.48+/-0.32 vs. 0.097+/-0.002 mu g/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 mu g/l) would correspond to a theoretical normal nadir GH of <= 0.27 mu g/l. Patients with GH nadir <= 0.3 mu g/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 <= 1 mu g/l had IGF-I >130% ULNR and mean GH-12 h of 0.93+/-0.24 mu g/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 <= 1 mu g/l. The degree of increased IGF-I levels and nadir GH after oGTT are correlated with the subtle abnormalities of daytime GH secretion. (AU)