Bone mass

Oral calcium has long been used for the treatment of osteoporosis, both in the form of dietary and pharmacological supplements. In patients with calcium deficiency, oral calcium at doses of 1000-1500 mg/day corrects a negative calcium balance and suppresses PTH secretion. Sufficient calcium intake is most important for the acciual of peak bone mass in the young, but is also considered the basis of most anti-osteoporotic regimens. In the elderly, supplementation with oral calcium and vitamin D reduces the risk of hip fracture by about 30 4-0%. 

LRP5 Loss-of-function (familial, autosomal recessive) Osteoporosis-pseudoglioma-syndrome (reduced bone mass)... 

Although many experiments have been performed, quantitative relationships between mechanical loads and bone adaptation do not yet exist. In vivo strain gauge studies have found a remarkable similarity of peak surface strains -2000 p.e at the midshaft of different bones across different animals at maximum activity. Measuring strains in adaptation studies would allow us to relate in vivo load changes to altered surface strains to adapted bone mass and strength. 

Amenorrhea in the adolescent population is of great importance because this is the time in the female life cycle when peak bone mass is achieved. The cause of amenorrhea and appropriate treatment must be identified promptly in this population because hypoestrogenism contributes negatively to bone development. Estrogen replacement, typically via an OC, is important. In addition, ensuring that the patient is receiving adequate amounts of calcium and vitamin D is imperative. 

Postmenopausal osteoporosis is a condition that affects millions of women and is characterized by low bone mass with microarchitectural deterioration of bone tissue that can... 

TABLE 53-2. Medical Conditions and Drugs Associated with Osteoporosis or Low Bone Mass... 

Under normal circumstances, the skeleton undergoes a dynamic process of bone remodeling. Bone tissue responds to stress and injury through continuous replacement and repair. This process is completed by the basic multicellular unit, which includes both osteoblasts and osteoclasts. Osteoclasts are involved with resorption or breakdown of bone and continuously create microscopic cavities in bone tissue. Osteoblasts are involved in bone formation and continuously mineralize new bone in the cavities created by osteoclasts. Until peak bone mass is achieved between the ages of 25 and 35, bone formation exceeds bone resorption for an overall increase in bone mass. Trabecular bone is more susceptible to bone remodeling in part owing to its larger surface area. 

Once the bone mineral density report is available, T-scores and Z-scores are useful tools in interpreting the data. The T-score is the number of standard deviations from the mean bone mineral density in healthy young white women. Osteoporosis is defined as a T-score at least -2.5 standard deviations below the mean (Table 53-3). Osteopenia, or low bone mass that eventually may lead to osteoporosis, is defined as a T-score between -2.5 and -1.0 standard deviations below the mean. The International Society for Clinical Densitometry recommends use of the WHO definition and T-scores for diagnosis of osteoporosis in postmenopausal women and men... 

In order to prevent certain risk factors and maximize peak bone mass, efforts must be directed toward osteoporosis prevention at an early age. 

Review bone densitometry (i.e., central DXA) for the presence of low bone mass (i.e., T-score below -2.5 in the spine or hip for osteoporosis or T-score below -1.5 with presence of other significant osteoporosis risk factors). 

Osteoporosis is an age-related disorder estimated to affect twice as many women as men.1 Characterized by loss of bone mass over a lifetime, it accounts for more than one million fractures annually with one of every five American women over 65 years old having one or more fractured bones.2 3 With the elderly projected to represent 25% of the population by 2030, the consequences of bone loss are a significant public health problem. 

Postmenopausal women (60-69 y) N=571 Observational Urinary mineral excretion, bone mass Self report No association between calcium excretion or bone mass in abstainers and coffee drinkers with similar smoking habits and degree of obesity. 

Pre-, peri-, and postmenopausal women (mean 44 y) N=48 Observational Changes in radial bone mass Not reported No significant relationships between bone mass and caffeine. 

Postmenopausal women (mean 66 y) N=85 Observational Bone mass 24-hour diet recall and diet history... 

Heaney, R., Bone mass, nutrition and other lifestyle factors, American Journal of Medicine, 95, 29S, 1993. 

Bauer, D. C., Browner, W. S., Cauley, J. A., Orwoll, E. S., Scott, J. C., Black, D. M., Tao, J. L., Cummings, S. R., Factors associated with appendicular bone mass in older women. The study of osteoporotic fractures research group, University of California, San Francisco., Annals of Internal Medicine, 118, 741, 1993. 

Eliel, L. P., Smith, L. C., Ivey, J. L., Baylink, D. J., Longitudinal changes in radial bone mass — dietary caffeine, milk, and activity, Calcified Tissue International, 35, 669 (Abstract), 1983. 

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