Evaluation of markers of bone and collagen turnover in patients with active and preclinical Cushing's syndrome and in patients with adrenal incidentaloma

Although steroid-induced negative effects on bone and collagen have been well described in corticosteroid-treated patients, few studies have extensively evaluated bone and collagen turnover in patients with endogenous Cushing's syndrome. In this work serum bone-Gla protein (BGP), C-terminal cross-linked telopeptide of type I collagen (ICTP) and N-terminal propeptide of type III procollagen (PIIINP) levels were determined in patients with active (n = 12) and preclinical (n = 6) Cushing's syndrome, adrenal incidentalomas (n = 35) and in healthy controls (n = 28). In patients with overt Cushing's syndrome, serum BGP (0.9 ± 0.2 ng/ml), ICTP (2.7 ± 0.2 ng/ml) and PIIINP (1.9 ± 0.2 ng/ml) levels were significantly lower (P <0.0001) than in controls (5.5 ± 0.2, 3.9 ± 0.2 and 3.2 ± 0.2 ng/ml respectively). In preclinical Cushing's syndrome, serum BGP (2.5 ± 0.8 ng/ml), ICTP (2.2 ±).1 ng/ml) and PIIINP (2.2 ± 0.2 ng/ml) levels were significantly lower than in normal subjects (P <0.0001, P <0.0001 and P <0.02 respectively), being similar to those recorded in over Cushing's syndrome. In patients with adrenal incidentaloma, serum BGP (4.2 ± 0.5 ng/ml) and ICTP (2.9 ± 0.2 ng/ml) levels were significantly lower than those found in controls (P <0.05 and P <0.001 respectively), while serum PIIINP levels (3.6 ± 0.2 ng/ml) did not differ from those of normals. In particular, 9/35 patients with adrenal incidentaloma had markedly depressed BGP levels (