Biochemical markers of acromegalic activity

Against a clinical score we compared the effectiveness of three biochemical markers of acromegalic activity: a) growth hormone response to i.v. thyrotropin-releasing hormone, b) growth hormone suppression one hour after an oral glucose load, c) basal plasma IGF-I levels. In 21 patients we obtained 39 observations comprising the four parameters. According to the clinical score, patients were divided into three groups: group I = patients before surgery; group II = improved but still clinically active; group III = clinically inactive. After i.v. thyrotropin-releasing hormone, abnormal observations increased although the patients improved clinically, so that this test was excluded from statistical analysis. Abnormalities in plasma IGF-I levels and in GH suppression after oral glucose were similarly frequent in the groups studied: both 100% in group I, both 71.4% in group II, 27.3% vs. 18.2% in group III (p > 0.05). Both tests made exactly the same contribution to the other's capacity to detect acromegalic activity: 3 out of 39 observations (5.1%). We conclude that basal plasma IGF-I is the single best biochemical marker to detect acromegalic activity, since it is statistically at least as useful as growth hormone suppression, and is far more simple for the patient and the laboratory.