Assessment of disease activity in acromegaly by means of a single blood sample: comparison of the 120th minute postglucose value with spontaneous GH secretion and with the IGF system.

OBJECTIVE: It has been suggested that the threshold of 1 micro g/l of GH nadir after glucose load for definition of controlled acromegalic disease proposed in the 2000 consensus statement should be lowered to 0.30. We evaluated these two cut-off values in comparison with IGF-I, ALS and IGFBP-3 in a group of acromegalic patients. With the aim of simplifying the follow-up protocol in these patients we also tested if one single sample taken after glucose load could replace the nadir value. DESIGN AND MEASUREMENTS: GH secretion was evaluated by oral glucose tolerance test (OGTT), and by studying spontaneous secretion (GH day curve) with sampling at hourly intervals from 08.00 to 18.00 h; from the day curve, mean (MGHDC) and minimum (TRGH) values were considered. IGF-I, ALS, and IGFBP-3 were measured in the basal state at the first testing. patients Fifty acromegalic patients (26-83 years, 31 females, 19 males) in various phases of disease activity. Forty-two patients had previously undergone pituitary surgery (10 also radiotherapy), 23 were treated with SMS analogues and three with dopamine agonist drugs.
RESULTS: The nadir GH value after glucose load correlated most significantly with the 120th-minute sample (R = 0.95). Comparison of the postglucose 120th minute at the two cut-off values with IGF-I, IGFBP-3 and ALS showed higher concordance of postglucose level at 0.3 with IGF-I, while concordance was similar for the two cut-off values with ALS and IGFBP-3. When the 120th minute postglucose GH value is lower than 1 micro g/l and IGF-I is within 2SD for age nearly all other parameters are normal. IGF-I correlated more with ALS (R = 0.78) than with IGFBP-3 (R = 0.50) and the latter was less concordant with GH secretion parameters than the previous two.
CONCLUSIONS: A sample taken at the 120th minute after glucose load, together with IGF-I and/or ALS evaluation can give sufficient information for a routine assessment of disease activity, both in the diagnosis and in the follow-up to treatment. If GH is lower than 1 micro g/l and IGF-I/ALS are normal, then the patient can be classified as 'nonactive' or 'controlled'; a pathological IGF-I and/or ALS value is a sign of disease activity irrespective of the GH values, while normal IGF-I/ALS with an elevated GH requires further assessment.