Insulin-like growth factor I and daily growth hormone profile in the assessment of active acromegaly

A poor correlation exists between growth hormone levels and the severity of disease in patients with acromegaly. It has been suggested that insulin-like growth factor I correlates better with the clinical condition thaN GH itself, but the presence of a correlation between GH and IGF-I is still a matter of debate. We therefore studied the fasting concentration of acid-extracted IGF-I and the daily GH profile (at 08.00, 12.00, 16.00, 20.00 h) in 28 acromegalic patients, both in basal condition and at different times after treatment. All patients studied before treatment exhibited a GH mean daily concentration always above 5 micrograms/l (range 5.15-1.47 micrograms/l), and IGF-I values (1.99-6.85 U/l) always above the normal range (0.38-1.90 U/l). During the follow-up after medical, surgical or radiation therapy we did not observe normalization of the IGF-I concentration for a GH day curve value above 5 micrograms/l. Compared with the GH day curve, a single morning GH value was slightly less sensitive and definitely less specific. The analysis of covariance evidenced a good correlation (P less than 0.001) between the GH day curve and IGF-I concentration during the first 6 months of medical as well as during the first year of radiation therapy, and after surgical treatment. Our data indicate that a single determination of acid-extractable IGF-I is as reliable as GH multiple sampling to assess the acromegalic disease activity.