Serum osteocalcin radioimmunoassay in bone diseases.

Osteocalcin (or bone Gla protein, BGP) is a non-collagenous vitamin K-dependent protein accounting for 1-2% of the total bone proteins. It represents a specific index of osteoblastic activity and directly reflects the bone turnover. Serum levels of osteocalcin were measured by a radioimmunoassay method. In 40 postmenopausal women with osteoporosis, mean serum BGP levels were lower than the normal range (3.69 +/- 1.35 ng/ml), whereas they significantly increased in 7 patients with osteomalacia (10.48 +/- 3.05 ng/ml), in 12 patients with secondary hyperparathyroidism (11.1 +/- 4.9 ng/ml) and in 41 patients with Paget's disease (12.09 +/- 6.5 ng/ml). Four patients with primary hyperparathyroidism showed very high BGP levels (64.0 +/- 32.3 ng/ml), which strikingly fell after the surgical removal of a parathyroid adenoma. These results confirm that the quantitation of serum osteocalcin is a specific and sensitive method in the diagnosis of bone disease, represents a useful index of bone turnover and is particularly helpful in the follow-up of patients with treated bone disease.

Calcitonin levels in normal subjects according to age and sex.

To evaluate the effect of age and sex on plasma calcitonin in human beings, the concentrations of the hormone were measured in 63 normal subjects aged 13-87 years of both sexes. In another study 30 healthy women were studied, 14 of them were pre-menopausal, 16 were post-menopausal. Plasma calcitonin was determined by means of a radioimmunoassay, using delayed tracer addition for increasing sensitivity. The antibody was produced in rabbits against pure synthetic human calcitonin and was specific for the aminoacid sequence 17 to 32 in the calcitonin molecule. A second antibody was used as a precipitating agent. A mean plasma calcitonin level of 71.3 +/- 37.0 SD pg/ml was observed. Women were found to have lower levels than men, the mean values being 63.4 +/- 34.7 pg/ml and 92.6 +/- 35.4 pg/ml respectively. The difference was statistically significant (P less than 0.005). No significant correlation was found between calcitonin levels and age of subjects. Premenopausal women, however, showed higher levels of plasma calcitonin than post-menopausal women, the mean values being 88.5 +/- 38.4 pg/ml and 54.0 +/- 33.6 pg/ml, respectively. This difference was also significant (P less than 0.01). Possible implications of these data are discussed.