Serum concentrations of procollagen I C-terminal propeptide (PICP) were studied in 74 patients with various forms of non-lethal osteogenesis imperfecta and 27 unaffected family members. Using the standard deviation (SD) score, PICP concentrations were found to be > or = -1 SD in 16%, between -1 and -2 SD in 26% and < or = -2 SD in 58% of the patients with osteogenesis imperfecta compared to healthy controls. PICP values were lowest in osteogenesis imperfecta type I (-2.4 +/- 0.4 SD, n = 37) followed by type III (-1.9 +/- 0.5 SD, n = 13) and type IV (-1.3 +/- 0.7 SD, n = 20). Four patients with osteogenesis imperfecta with an atypical clinical course had normal or even elevated levels which may indicate heterogeneity in the underlying primary defects. In osteogenesis imperfecta type I, PICP concentrations proved to be a helpful serum marker for pedigree screening. Osteocalcin was high in 25 of 28 patients with osteogenesis imperfecta in the first decade but only in 1 of 18 older patients. Insulin-like growth factor-I was within the normal range in 53 cases of osteogenesis imperfecta, decreased in 2 and elevated in 3 patients. We conclude that PICP concentration is a useful parameter in the clinical management of osteogenesis imperfecta, including the assessment of future therapeutic interventions.
In addition to the alendronate Osteoporosis Intervention Trial (FOSIT) core protocol 901-0A of 1908 enrolled patients, the use of peripheral quantitative computed tomography (pQCT) was explored for the assessment of response to therapy. Bone mineral and strength related parameters at two different sites at the distal radius were explored in a subset of the multicenter core study. One hundred and three patients were entered into the substudy and given either a daily dose of 10 mg of alendronate or placebo for 1 year. Measurements were done at months 0, 3, 6, and 12. Inclusion criteria were bone mineral density (BMD) measurements at the lumbar spine of −2 SD. The response to therapy was assessed by dual-energy X-ray absorptiometry in the lumbar spine and the hip, and by pQCT in the ultradistal and the shaft sites of the radius. In line with the FOSIT core study, alendronate increased BMD at the lumbar spine and the hip, and it decreased the serum biochemical markers of bone turnover. The substudy showed differences between the therapy and placebo group in trabecular bone density (8.4%, p = 0.095), in total density (6.8%, p = 0.009), and in the bone strength index (BSI) (15.6 mm 3 , p = 0.037) at the ultradistal site due to treatment and no changes at the radius shaft. A significant correlation was observed between percentage changes from baseline in BMD of the lumbar spine, and in total density and bone strength at the ultradistal radius site in the treatment group, but not in the placebo group. Thus, the ultradistal radius site did respond to alendronate therapy. The increased bone density accompanied a significant gain in the BSI at the ultradistal site, a finding that might help explain the reduced wrist fractures in the alendronate Fracture
Calcitonin and its carboxyl-terminal flanking peptide (PDN-21), also encoded by the calcitonin gene, were measured by RIA in unextracted serum of normal subjects and patients with primary hyperparathyroidism and surgically verified and suspected medullary thyroid carcinoma. Serum PDN-21 was detectable (greater than 0.005 ngeq/ml) in the large majority of normal subjects (92%), and the values increased significantly more in men than women (4.8- and 2.0-fold, respectively; P less than 0.01) in response to 1-min iv calcium injections. Calcitonin was detectable (greater than 0.025 ngeq/ml) in only 25% of normal subjects before iv calcium and became measurable after iv calcium in 88% of men and 41% of women. In patients with chronic hypercalcemia due to primary hyperparathyroidism, PDN-21 and calcitonin were within normal limits. In normal subjects, iv pentagastrin (0.5 microgram/kg BW) did not increase PDN-21, and calcitonin remained undetectable. In 41 medullary thyroid carcinoma patients, basal PDN-21 and calcitonin levels were increased similarly, and they were stimulated in response to iv calcium or iv pentagastrin. In 5 siblings of medullary thyroid carcinoma patients, PDN-21 and calcitonin were increased in response to iv pentagastrin, and we suspect C-cell hyperplasia or medullary thyroid carcinoma. In conclusion, a diagnostically useful RIA for the measurement of PDN-21 in unextracted serum which complements calcitonin measurements has been developed.
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