Serum levels of bone Gla protein (osteocalcin, BGP) and carboxyterminal propeptide of type I procollagen (PICP) in acromegaly: effects of long-term octreotide treatment.

We measured serum concentrations of bone Gla-protein (osteocalcin, BGP) and carboxyterminal propeptide of type I procollagen (PICP) in 14 patients with active acromegaly. Blood was collected at 0800 for measurement of bone Gla-protein (BGP), carboxyterminal propeptide of type I procollagen (PICP), and insulin-like growth factor I (IGF-I); growth hormone (GH) was then determined at 15-minute intervals for 3 hours and the integrated mean was calculated. The same protocol was repeated at regular intervals during treatment with the long-acting somatostatin analog, octreotide, 150-450 micrograms/day for 6-33 months (median 15). In a case-control analysis, serum BGP concentrations recorded in the acromegalic patients were significantly elevated (14.2 +/- 4.2 micrograms/liter versus 8.0 +/- 3.3 micrograms/liter, P < 0.001). Octreotide treatment induced a roughly parallel reduction in serum GH, IGF-I, and BGP. We found a significant positive correlation between BGP levels recorded before and during therapy and the logarithm of corresponding mean GH levels (r = 0.67, P < 0.001). Also IGF-I concentrations were positively correlated with BGP (r = 0.66, P < 0.001). On the other hand, PICP levels recorded in the acromegalics did not differ from control subjects (146 +/- 46 micrograms/liter versus 127 +/- 44 micrograms/liter, NS) and no correlation was found between either GH and PICP or IGF-I and PICP. To conclude, the present data are compatible with the view that GH and IGF-I play an important role in the control of BGP but not PICP production. It could be that BGP and PICP are submitted to different hormonal modulation.