Low serum levels of intact osteocalcin in patients with congestive heart failure.

Impaired bone metabolism is a frequent complication following heart transplantation. Little is known, however, about possible alterations in bone turnover of pretransplant patients with congestive heart failure (CHF). We therefore studied biomarkers of bone turnover in 21 male patients with CHF (New York Heart Association [NYHA] classification > II) compared with 21 controls (NYHA classification < II). Biomarkers of bone formation (intact osteocalcin and carboxy-terminal propeptide of type I collagen), markers of bone resorption (N-telopeptide and C-telopeptide of type I collagen), undercarboxylated osteocalcin (an indicator of fracture risk), and concentrations of calcium, parathyroid hormone, and vitamin D metabolites (25-hydroxyvitamin D and calcitriol) were measured in fasting blood samples. Serum levels of intact osteocalcin were 44.5% lower (P < 0.01), and the ratio of undercarboxylated-to-intact osteocalcin was 113% higher (P < 0.01) in the patients in comparison with the controls. Moreover, patients had 34% lower 25-hydroxyvitamin D levels (P < 0.01) and 22% lower calcitriol levels (P < 0.05) than the controls. The bone resorption markers, N-telopeptide and C-telopeptide; the bone formation marker, carboxy-terminal propeptide of type I collagen; parathyroid hormone levels; and albumin-adjusted serum calcium concentrations did not differ between patients and controls (all P values > 0.05). In summary, there were no biochemical signs of enhanced bone collagen resorption in pretransplant CHF patients. However, the low serum levels of intact osteocalcin and the high ratio of undercarboxylated-to-intact osteocalcin deserve further consideration.