Comparative study of insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) level and IGF-I/IGFBP-3 ratio measurements and their relationship with an index of clinical activity in the management of patients with acromegaly

To evaluate the utility of measuring the serum insulin-like growth factor (IGF)-binding protein-3 (IGFBP-3) level and the IGF-I/IGFBP-3 ratio in the management of acromegalic patients, we comparatively studied the basal concentration of the aforementioned parameters with determination of plasma IGF-I levels and an index of clinical activity of acromegaly in 16 newly diagnosed acromegalic patients (aged 34 to 64 years) before and after hypophysectomy. After adenomectomy, 10 patients remained with "active" disease and six were "cured." Twenty-nine healthy sex- and age-matched volunteers were also studied. Comparison of individual values between untreated acromegalic patients and control subjects showed that none of the patients had overlapping values for IGF-I, whereas five of 16 and three of 16 patients had overlapping values for serum IGFBP-3 and IGF-I/IGFBP-3 ratio, respectively. When we compared the study parameters between the patients who remained with active disease after adenomectomy and the controls, two of 10 had overlapping values for IGF-I, but six of 10 and five of 10 had overlapping values for serum IGFBP-3 and IGF-I/IGFBP-3 ratio, respectively. Moreover, comparison of these parameters between cured and active patients after hypophysectomy showed that none had overlapping values for IGF-I, whereas three of six and one of six had overlapping values for serum IGFBP-3 and IGF-I/IGFBP-3 ratio, respectively. All biochemical variables studied showed significant relationships with an index of clinical activity of disease. In conclusion, our results seem to indicate that among determinations of plasma IGF-I, serum IGFBP-3, and the ratio IGF-I/IGFBP-3 in the evaluation of acromegalic patients, measurement of the plasma IGF-I level has the most discriminative value in the management of these patients.