Tc-99m HMDP bone scintigraphic findings in association with concurrent serum osteocalcin measurements

Osteocalcin is a noncollagenous bone protein produced by osteoblasts. Increase in serum osteocalcin level reflects osteoblast activity with acceleration of bone formation. To evaluate the correlation of Tc-HDP bone scintigraphic findings and concurrent serum osteocalcin, serum osteocalcin values of 40 consecutive patients were measured by radioimmunoassay at the time of initial referral for bone studies. These patients, all males aged 23-93, were studied for various disease entities, including prostate carcinoma. The results of the assay were categorized into three groups (gp) as follows: 17 at normal (1.8 to 6.6 ng/ml) level (gp 1), 21 low (gp 2), and two high (gp 3). Only one bronchogenic carcinoma patient with a high level had a right iliac lesion suggesting metastasis. The bone scans of nine patients with normal or low levels showed positive metastases. Two patients with stress fractures as shown on bone scans had normal levels. The images of patients with disparity between serum osteocalcin and positive bone lesions may be interpreted as follows: Instead of osteoblastic activity resulting in the synthesis and/or release of osteocalcin, area(s) of increased uptake in the bone scan may be predominantly reflecting increased regional blood flow and decreased sympathetic tone, resulting in an increase in bone-agent deposition.