Monitoring disease activity using GH and IGF-I in the follow-up of 501 patients with acromegaly

P>Context The aims of treatment in patients with acromegaly are to achieve serum GH/IGF-I concentrations associated with cure or normalization of mortality and alleviation of symptoms. Objective and methods Using the West Midlands Acromegaly database (n = 501) we investigated the reliability of basal fasting GH in predicting nadir or mean GH during oral glucose tolerance test (OGTT) or GH day curve (GHDC), respectively, the degree of discordance between disease activity measured by GH and IGF-I values and the effect of radiotherapy on the above relationships. In total 773 OGTT and 507 GHDC were performed. Results Basal fasting GH was strongly correlated with nadir/mean GH on OGTT/GHDC (r = +0 center dot 87, P < 0 center dot 0001, r = +0 center dot 93, P < 0 center dot 0001, respectively). A basal GH < 2 center dot 5 mu g/l was associated with a nadir/mean GH during OGTT/GHDC < 2 center dot 5 mu g/l in 98 center dot 6% and 88 center dot 2% of cases, respectively. Elevated IGF-I was seen in 32 center dot 4% and 46 center dot 4% of patients with GH nadir values during OGTT < 1 and < 2 center dot 5 mu g/l, respectively, and in 21 center dot 2% and 45 center dot 9% of GHDC with mean GH < 1 and < 2 center dot 5 mu g/l, respectively. Radiotherapy increased the discordance in GH and IGF-I as markers of disease activity at GH < 2 center dot 5 mu g/l (elevated IGF-I-values when OGTT nadir GH < 2 center dot 5 mu g/l: radiotherapy 55 center dot 5% vs. no radiotherapy 36 center dot 9%, P = 0 center dot 002). Conclusions There is a close relationship between a basal fasting GH < 2 center dot 5 mu g/l and nadir/mean GH < 2 center dot 5 mu g/l during OGTT/GHDC. There is a large discordance between disease activity when assessed by GH and IGF-I which is further increased by radiotherapy. These observations illustrate the challenge of defining appropriate biochemical end-points to achieve control of disease and normalization of mortality in acromegaly.