Monitoring of treatment success in patients with acromegaly: the value of serum insulin-like growth factor binding protein-3 and serum leptin measurements in comparison to plasma insulin-like growth factor I determination

The aim of the present study was to determine the value of serum insulin-like growth factor binding protein-3 (IGFBP-3) and serum leptin measurements in comparison with plasma insulin-like growth factor I (IGF-I) measurements as indicators of treatment success in patients with acromegaly. Thirty-five acromegaly patients, 25 female and 10 male, divided into groups of patients with postadenomectomy "active" acromegaly (n = 20) and patients with postadenomectomy "controlled" acromegaly (n = 15), and 44 healthy volunteers sex- and age-matched with the acromegaly patients were included in the present study. We comparatively analyzed plasma IGF-I, serum IGFBP-3, and serum leptin levels in the aforementioned groups. Because serum leptin has sex dimorphism, the groups were divided into sexes when leptin was evaluated. As expected, the patients with active acromegaly had significantly higher mean values of plasma IGF-I and serum IGFBP-3 and lower mean values of serum leptin (only in women) than the control group. However, individual evaluation showed that 1 of 20, 9 of 20, and many patients with postadenomectomy active acromegaly patients had values that overlapped values of control subjects for plasma standard deviation score (SDS)-IGF-I, serum SDS-IGFBP-3, and sex-adjusted serum leptin, respectively. Application of the receiver operating characteristic (ROC) curves method shows that plasma IGF-I measurement has the best discriminatory power to differentiate patients with postsurgical active acromegaly from healthy people. Its area under the curve (AUC) was 0.95, with a sensitivity and specificity of 86% and 94%, respectively. Its positive and negative likelihood ratios were 14 and 0.15. Serum IGFBP-3 has certain discriminatory power, its AUC being 0.89, with a sensitivity and specificity of 83% and 77%. Its positive and negative likelihood ratios were 3.6 and 0.22. Serum leptin, both in women and in men, has a poor performance with sensitivity and specificity of 53% and 50% for women and 55% and 56% for men and positive and negative likelihood ratios of 1.06 and 0.94 for women and 1.26 and 0.8 for men. Application of the ROC curves method and the determination of positive and negative likelihood ratios in comparative evaluation of serum IGFBP-3 and serum leptin with plasma IGF-I as indicators of treatment success in acromegalic patients showed that neither serum IGFBP-3 nor serum leptin determinations have accuracy better than or similar to that of plasma IGF-I for monitoring treatment success in acromegaly patients. Serum IGFBP-3 is accurate but does not increase accuracy for age-adjusted plasma IGF-I, whereas determination of serum leptin level has no value in monitoring these patients.