Effect of high parathyroid hormone level on bone mineral density in a vitamin D-sufficient population: Korea National Health and Nutrition Examination Survey 2008-2010

Association between Bone Mineral Density and Nutritional Status, Body Composition and Bone Metabolism in Older Adults

PURPOSE

To identify an association between bone mineral density (BMD) and nutritional status, body composition and bone metabolism in older patients.

METHODS

Cross-sectional study, involving older adults, with osteopenia/osteoporosis and with normal BMD. The mineral density of the lumbar spine from L1 to L4 and the proximal region of the femur was assessed using dual energy X-ray absorptiometry. Biochemical analyzes were performed of 25(OH)-D, calcium and parathormone. Weight, knee height, and abdominal (AC), mid-upper arm (MUAC) and calf (CC) circumferences were measured. The percentage of body fat (%BF) and Fat-Free Mass (FFM) were quantified by electrical bioimpedance analysis. The Body Mass Index (BMI) was calculated. The statistical analysis used bivariate and multivariate, parametric and/or non-parametric tests, and was considered significant when p <0.05.

RESULTS

Of the total 51 older adults assessed, 30 of them (58.8%) were diagnosed with osteopenia/osteoporosis. Body weight (p = 0.001), BMI (p = 0.001), % BF (p = 0.030) and serum concentrations of 25(OH)-D (p = 0.003) were higher in the group without changes in BMD. BMI and serum levels of 25(OH)-D demonstrated a positive correlation with the BMD of all bone compartments and the AC displayed a positive correlation with the lumbar vertebrae. In the logistic regression models, adjusted for sex and age, the BMI and the serum concentration of 25(OH)-D were presented as a protective factor against osteopenia/osteoporosis.

CONCLUSIONS

Higher body weight, BMI, AC and %BF, and sufficient serum levels of vitamin D, were shown to be promoters of BMD.

Effects of PTH and PTH Hypersecretion on Bone: a Clinical Perspective

PURPOSE OF REVIEW

Hyperparathyroidism may be due to an autonomous hypersecretion of parathyroid hormone (PTH) or occurs in response to a number of physiological stimuli. A number of recent findings have provided new insights into the importance of the calcium-parathyroid-vitamin D axis to bone in normal physiology and pathological conditions.

RECENT FINDINGS

PTH is known to affect bone microarchitecture with different effects on cortical and trabecular bone compartments. In trabecular bone, PTH may exert anabolic effects, whereas PTH promotes bone resorption in cortical bone. Vertebral fractures are prevalent in primary hyperparathyroidism (PHPT), and patients seem to fracture at higher values of bone mineral density (BMD) than patients with osteoporosis. This may be explained by changes in bone microarchitecture, which cannot be detected by measuring BMD. Even in mild PHPT, bone seems to benefit from parathyroidectomy. In secondary hyperparathyroidism, bone seems much more susceptible to fracture with insufficient levels of vitamin D compared with a replete vitamin status. If elevated PTH levels cannot be explained by conditions known to cause secondary hyperparathyroidism, the condition is termed normocalcemic PHPT, which also has been associated with an increased risk of fractures. Hyperparathyroidism is harmful to bone, which is why it is of importance to normalize PTH levels either by parathyroidectomy in PHPT or by counteracting conditions known to increase PTH in secondary hyperparathyroidism.