We evaluated serum bone Gla-protein (osteocalcin, BGP), carboxyterminal propeptide of type I procollagen (PICP) and aminoterminal propeptide of type III procollagen (PIIINP) in 15 patients with active acromegaly (6M aged 27-54, 4 PMF aged 39-51, 5MP aged 54-65 years), 12 with active Cushing's syndrome [(CS) 2M of 32 and 42 years; 4PMF aged 25-40; 6MF aged 50-64)] and controls evenly matched for age, sex and menstrual status. Patients with acromegaly were evaluated before and at regular intervals on octreotide treatment (50-150 micrograms t.i.d., s.c.); the duration of the follow-up was 5-49 months (median 28). Endocrine evaluation included measurements of serum GH, IGF-I, BGP, PICP and PIINP. In a case-control analysis, acromegalic patients showed increased BGP (14.3 +/- 2.1 vs 8.3 +/- 2.1 ng/ml p < 0.001) and PIIINP concentrations (4.8 +/- 1.4 vs 3.1 +/- 0.7 micrograms/l, p < 0.02). During octreotide treatment we observed a roughly parallel decline of GH, IGF-I and BGP. BGP and log-transformed 24-h mean GH concentrations were positively correlated (r = 0.48, p < 0.001) as was the case for BGP and IGF-I (r = 0.43, p < 0.001). Also PIIINP correlated with log-transformed GH (r = 0.58, p < 0.001) and IGF-I (r = 0.35, p < 0.05). Serum PICP did not differ in the two groups (152 +/- 55 vs 120 +/- 55 micrograms/l, NS) and did not correlate either with GH or IGF-I. Patients with CS were evaluated measuring serum and urinary cortisol (UFC), ACTH, BGP, PICP, PIIINP.(ABSTRACT TRUNCATED AT 250 WORDS)