A comparison of different methods for diagnosing acromegaly

The present study was designed to assess the diagnostic value of different single measurements in comparison to the classic time-consuming method, the oral glucose tolerance test (OGTT), in acromegaly.

IGF-I, free IGF-I, 24-hour-urinary GH (uGH), serum IGFBP-3 and 24-hour-urinary IGFBP-3 (uIGFBP-3) were measured in 12 patients with untreated active acromegaly, in 29 patients who had been treated but were not cured, in 13 patients with cured acromegaly and in 14 healthy control subjects, and compared with the results of the OGTT.

In all patients with active acromegaly, whether they had been treated or not, nadir GH in OGTT was > 3 mU/l, whereas nadir GH was < 1.8 mU/l in the cured patients and the control subjects. In patients with untreated active acromegaly IGF-I, free IGF-I, uGH and IGFBP-3, but not uIGFBP-3, were significantly higher than in healthy individuals (P < 0.0001). Only IGF-I values did not overlap with the control group. In those patients with acromegaly who had been treated but not cured these parameters overlapped with the control group. In patients with acromegaly there was a significant correlation between nadir GH levels in OGTT and IGF-I (r = 0.71), free IGF-I (r = 0.76), IGFBP-3 (t = 0.73) and uGH (r = 0.81) (P < 0.0001), but no correlation with uIGFBP-3.

Only be means of the OGTT could patients with active acromegaly be completely distinguished from the control subjects and from cured patients. IGF-I, free IGF-I, IGFBP-3 and uGH were useful in the diagnosis of acromegaly, but of limited value in the follow-up of acromegalic patients after treatment. The determination of free IGF-I, which has yet not been investigated in acromegaly, offered no advantage over that of total IGF-I and IGFBP-3; uIGFBP-3 was not useful in the diagnosis of acromegaly.