Role of insulin-like growth factor-I in primary osteoporosis: a correlative study

Calcitriol treatment in patients with low vitamin D levels

The aim of the the study is to compare the effects of cholecalciferol and calcitriol on bone mineral metabolism in women with vitamin D deficiency. Calcitriol was associated with a significant increase in bone mineral density at the lumbar spine in patients with low vitamin D levels.

PURPOSE/INTRODUCTION

Active vitamin D analogs may have larger impact in decreasing bone loss and fracture rate compared to cholecalciferol in osteoporosis. However, their effects in the treatment of vitamin D deficiency compared to cholecalciferol are not clear. The aim of the present study is to compare the effects of cholecalciferol and calcitriol on bone mineral metabolism and bone mineral density in pre- and postmenopausal women with vitamin D deficiency.

METHODS

This was a 6-month prospective, open-label, controlled clinical trial. Eligible 120 participants were pre- and postmenopausal women diagnosed with vitamin D deficiency. Forty-three subjects (group 1) received 1000 IU of cholecalciferol and 1 g of calcium daily. The other 77 subjects (group 2) received 0.5 μg calcitriol in addition to 400 IU of cholecalciferol and 1 g of calcium daily.

RESULTS

Oral vitamin D supplementation did not increase bone mineral density after 6 months of intervention in group 1. On the other hand, bone mineral density at the lumbar spine increased from 0.809 ± 0.172 to 0.848 ± 0.161 g/cm² in group 2 patients (p < 0.017 vs baseline).

CONCLUSIONS

Oral daily calcitriol was associated with a significant increase in bone mineral density at the lumbar spine in patients with low vitamin D, elevated PTH, and osteoporosis.

Age-related changes in cortical bone content of insulin-like growth factor binding protein (IGFBP)-3, IGFBP-5, osteoprotegerin, and calcium in postmenopausal osteoporosis: a cross-sectional study

Serum GH and IGF-I levels decline with increasing age, whereas osteoprotegerin (OPG) increases. IGFs as well as OPG are present in bone matrix and mediate the effects of many upstream hormones (e.g. estrogen). To evaluate whether changes in these proteins may to some extent explain the decrease in bone mass in postmenopausal or senile osteoporosis, we measured bone contents of IGF-I, IGF-II, IGF binding protein (IGFBP)-3, IGFBP-5, and OPG in combined extracts obtained after EDTA and guanidine hydrochloride extraction in 60 postmenopausal women aged 47-74 (mean, 63) yr with a previous distal forearm fracture and a hip or spine Z-score less than 0. We found age-related increases in IGFBP-3 (r = 0.35; P < 0.01), IGFBP-5 (r = 0.59; P < 0.001), and OPG (r = 0.36; P < 0.01) in cortical bone, significantly inversely correlated with femoral neck and lumbar spine BMD. A correlation between age and OPG was also detected in trabecular bone (r = 0.27; P < 0.05). A pronounced age-related decrease in cortical calcium contents (r = -0.60; P < 0.001), positively correlated with femoral neck and lumbar spine BMD, was also found. No age-related changes were detected for IGF-I or IGF-II. The present study demonstrates age-related changes in cortical bone contents of IGFBPs, calcium, and OPG, possibly related to the pathophysiology of postmenopausal osteoporosis. As for OPG, our findings probably represent compensatory responses to increased osteoclastic resorption.

Fracture risk is increased in patients with GH deficiency or untreated prolactinomas--a case-control study

OBJECTIVE

The pituitary secretes many hormones of significance to bone turnover and thus skeletal integrity. The aim of this study was to examine fracture risk in patients with pituitary disorders with special reference to GH deficiency and hyperprolactinaemia.

DESIGN

Case-control study.

MEASUREMENTS

Fracture occurrence.

PATIENTS

A self-administered questionnaire was issued to 537 consecutive patients with pituitary disorders excluding Cushing's disease. A total of 426 (79%) returned the questionnaire and 422 of these could be analysed. Each respondent was compared to three age- and gender-matched control respondents to the same questionnaire drawn randomly from the background population.

RESULTS

The patients had a mean age of 51.4 +/- 14.8 years. One hundred and eight patients had acromegaly, 86 had prolactinomas, 136 had non-functioning pituitary adenomas (NFPA), 23 had craniopharyngiomas, and 73 had other types of pituitary disorders. For the total group the fracture risk was not elevated either before or after confirmed diagnosis compared to controls. However, among the patients with prolactinomas, the fracture risk was significantly increased before (relative risk, RR = 1.6, 95% CI: 1.1--2.3) but not after diagnosis. In patients with NFPA, fracture risk was borderline significantly elevated following diagnosis (RR = 1.6, 95% CI: 1.0--2.6). Patients with subnormal stimulated peak GH values suggestive of GH deficiency had a significantly higher risk of fractures after diagnosis than patients who had normal stimulated peak GH values (odds ratio, OR = 4.90, 95% CI: 1.10--21.88).

CONCLUSIONS

Untreated prolactinomas were associated with a significant increase in fracture risk. Growth hormone deficiency was also associated with a higher fracture risk.

Omega-3 polyunsaturated fatty acids and skeletal health

This minireview on skeletal biology describes the actions of prostaglandins and cytokines involved in the local regulation of bone metabolism, it documents the role of lipids in bone biology, and it presents relationships between fatty acids and other factors that impact skeletal metabolism. The data presented herein show consistent and reproducible beneficial effects of omega-3 (n-3) fatty acids on bone metabolism and bone/joint diseases. Polyunsaturated fatty acids modulate eicosanoid biosynthesis in numerous tissues and cell types, alter signal transduction, and influence gene expression. These effects have not been explored in the skeletal system. Future research on n-3 fatty acids in bone biology should focus on the following two aspects. First, the further elucidation of how n-3 fatty acids alter biochemical and molecular processes involved in bone modeling and bone cell differentiation, and second, the evaluation of the potential pharmaceutical applications of these nutraceutical fatty acids in maintaining bone mineral status and controlling inflammatory bone/joint diseases.