Updated: Aug 21, 2008
The World Health Organization (WHO) defines osteoporosis as a bone density (or bone mass) at least 2.5 standard deviations below peak bone mass (defined as the bone mass achieved by healthy adults aged 18-30 y). Standard deviation from the mean peak bone mass is termed the T score. Thus, a T score of the lumbar spine or hip at least 2.5 standard deviations below the norm defines osteoporosis.
Although functionally valid for adults, this definition creates difficulty when evaluating pediatric patients. Children have not attained peak bone mass, and sufficient data correlating bone density with fractures are not available. Although preliminary studies have examined the role of lumbar spine bone density and the risk of fracturing in children with burn injuries, more extensive population-based studies have not been conducted. Therefore, the official definition of osteoporosis does not pertain to children at the present time. However, at a National Institutes of Health (NIH) Consensus Conference in 2000, osteoporosis was defined as a skeletal disorder characterized by compromised bone strength that predisposes to an increased risk of fracture.1 Adult-onset osteoporosis also involves loss of bone trabecular structure; however, no evidence indicates that this occurs in children.
Encouragingly, at the First Pediatric Consensus Development Conference on the use and interpretation of bone density studies in children (sponsored by the International Society for Clinical Densitometry and held in Montreal in June 2007) pediatric osteoporosis was defined as bone density Z score below -2, in combination with a fracture.2,3,4,5 Z scores are now available for lumbar spine, hip, and total body because of a recently published NIH-sponsored multicenter study that established normative values of bone density and bone mineral content for these 3 parameters. The term osteopenia is no longer used when related to pediatric bone density or bone mineral content.
Low bone density in children involves the net loss of bone. Bone density is currently a 2-dimensional measurement. It is the quotient of the bone mineral content (BMC) measured in grams by absorptiometry in a specified bone region (eg, hip, lumbar spine), divided by the bone area (BA) in cm2 to give a reading in g/cm2. This 2-dimensional method of assessing bone density is limited because changes in bone volume and, therefore, bone strength cannot be detected. This leads to an inaccurate estimation of the severity of bone loss or the skeletal response to treatment. Pathways to decreased bone density all lead to an imbalance between the rate of bone formation and the rate of bone resorption. Thus, low-turnover conditions, such as chronic liver disease, burn injuries, or conditions that affect bone marrow (eg, malignancies) or their treatments, may result in a reduction of bone formation.
Other high-turnover states, such as Paget disease or hyperparathyroidism, can result in an increase in bone resorption. Interestingly, almost all preterm infants fall into this group. Because most calcium is transmitted from mother to fetus during the third trimester, infants born prematurely do not receive all the calcium their body needs to normally mineralize. With rapid postnatal increase in bone turnover, fewer opportunities are available for the bones to mineralize.6 Furthermore, most of these children receive total parenteral nutrition (TPN) for at least the first 3 weeks of life. TPN solutions are contaminated with aluminum; however, aluminum load has been decreased by more attention to additives. In addition, calcium and phosphorus requirements cannot be met by TPN in any age group, and the infant, especially the very premature infant, presents with hypophosphatemic metabolic bone disease.
The mechanisms resulting in secondary bone loss also stem from other adaptations to trauma and infection or threat of infection. These include the stress response, in which endogenous glucocorticoids may act in the same manner as exogenously administered steroids. These compounds cause an initial increase in osteoblast production of the receptor activator of nuclear transcription factor kappa B ligand (RANKL), which stimulates marrow to produce osteoclastic cells, increasing bone resorption. However, steroids also promote osteoblast apoptosis and reduce marrow cell osteoblast differentiation, eventually leading to a low-turnover bone loss or adynamic bone.
The other mechanism now linked to bone loss is the inflammatory response. This involves the production of the cytokines interleukin (IL)-1 beta and IL-6, as well as tumor necrosis factor (TNF) alpha. These are all capable of increasing bone resorption via stimulation of osteoblast production of RANKL.
Data that indicate the frequency of osteopenia in children are inadequate. The rare condition of idiopathic juvenile osteoporosis had been reported in 60 cases through 1991. By contrast, vertebral fracture prevalence attributed to osteoporosis in elderly women in the United States and Western Europe may be as high as 25%. As many as 54% of American postmenopausal women are estimated to have osteopenia, as defined by a T score between -1 and -2.5; an additional 30% are estimated to be osteoporotic, with a T score below -2.5.
The prevalence of osteoporosis worldwide (outside the United States and western Europe) varies. For example, the incidence of hip fracture in Koreans has increased from 3.3 per 10,000 to 13.3 per 10,000 between 1991 and 2001. In a 2005 study in Tehran, women aged 60-69 years had a 32.4% prevalence of spinal osteoporosis and a 5.9% prevalence of femoral osteoporosis, in contrast to a prevalence in similarly aged men of 9.4% and 3.1%, respectively. In Taiwan, the prevalence was 11.35% for women and 1.35% for men older than 50 years, based on bone density determinations.
Contributing factors to mortality and morbidity, especially in the elderly, are primarily related to trauma. These factors include falls with resultant hip fractures necessitating immobilization with resultant pulmonary embolism. In extreme cases, including idiopathic juvenile osteoporosis and osteopenia in immobile children with severe developmental delay, crippling bony deformities may lead to cardiopulmonary compromise.
Caucasians are at the greatest risk for fractures, whereas blacks and Asians appear to be at the lowest risk.
Osteoporosis mainly affects postmenopausal women and the elderly of both sexes. The protective effects of estrogens on bone are well known. During menopause, women lose their estrogen-producing capacity and develop a greater risk for significant osteoporosis.
Classic osteoporosis is a disease of adulthood. Children present with many forms of bone loss from various causes. The roots of adult disease are believed to begin in childhood, but this concept is challenged by the argument that osteoporotic bone from whatever origin is replaced by newer intact bone as bone undergoes modeling.
In children, low bone density (formerly termed osteoporosis) can develop because of low bone formation (low bone turnover) or high bone resorption (high bone turnover).
The following conditions elicit low bone formation:
Conditions giving rise to high bone turnover include the following:
Because of the availability of kits to measure biochemical markers of bone turnover, the use of bone histology obtained by iliac crest bone biopsy is no longer routine. Histology for bone biopsies is generally carried out using quantitative histomorphometry. For patients older than 10 years, administer tetracycline or one of its analogs 14 days before biopsy and then 2 days prior to biopsy. Using one of several specialized orthopedic needles, obtain a biopsy sample consisting of a 6-mm core of trabecular bone tissue.
When processed, the amounts of mineralized bone, unmineralized bone, and bone surface can be quantitated. In addition, the tetracycline binds to newly calcified bone at the mineralization front, which is the boundary between mineralized bone and unmineralized matrix where new bone forms. Each time a dose of tetracycline is administered, it forms a band at the mineralization front that can be detected under a fluorescent microscope. The distance between the 2 fluorescent bands can be quantitated. When divided by the time interval between doses and multiplied by the length of bone surface taking up the tetracycline yields, the rate of new bone formation is achieved. The eroded or resorbed bone surface also can be quantitated, and all can be compared to reference values for age.
Perform these studies if analysis of bone markers and other biochemical determinations are inconclusive regarding the nature of the activity of the bone in a particular condition. These studies also form the basis for validating the biochemical bone marker analyses.
Therapy includes antiresorptive agents such as bisphosphonates (eg, alendronate, risedronate, pamidronate). Hormone replacement therapy (eg, estrogen, estrogen analogs) does not have a role in pediatric therapy.
These agents prevent bone loss from diminishing bone mass on an ongoing basis. They are available in parenteral and oral dosage forms for acute and chronic treatment, respectively.
Inhibits normal and abnormal bone resorption. Appears to inhibit bone resorption without inhibiting bone formation and mineralization. Administered IV, usually 2 doses with a 1-wk interval. Approved for use in hypercalcemia of malignancy and Paget disease. Has also been used in children with osteopenic bone disease.
60-90 mg/dose IV administered over 8-24 h; dilute in dextrose and water solutions
Dose based on serum calcium measurements
Not established; experimental studies use 1.5 mg/kg/dose IV; not to exceed 90 mg/dose (published results are promising)
Calcium or vitamin D may antagonize the antihypercalcemic effects of the drug
Documented hypersensitivity; hypocalcemia, cardiac failure, and renal impairment
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Carcinogenicity and mutagenicity are not observed; decreased fertility and increased mortality observed in rats when administered PO; no known effects on breastfeeding; monitor hypercalcemia-related parameters, such as serum levels of calcium, phosphate, magnesium, and potassium once treatment begins; adequate intake of calcium and vitamin D is necessary to prevent severe hypocalcemia; caution when administering bisphosphonates in patients with active upper GI problems
PO bisphosphonate approved as an antiresorptive agent to treat Paget disease and postmenopausal osteoporosis.
Paget disease: 40 mg PO qam 30 min before first food or beverage; continue treatment for 6 mo
Postmenopausal osteoporosis treatment: 10 mg PO qam 30 min before first food or beverage; alternatively, 70 mg PO qwk
Administer dose with 6-8 oz of plain water
Not established
Dietary supplements, food, and medicines may interfere with absorption; medications (eg, antacids) interfere with absorption; histamine receptor antagonists (eg, ranitidine, cimetidine) can interfere with absorption; nonsteroidal anti-inflammatory agents can exacerbate inflammatory effects
Documented hypersensitivity; limited data in small open-labeled studies have been published
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
GI conditions (eg, duodenitis, gastritis, gastroesophageal reflux disease, ulcers) may worsen; renal functional impairment may reduce excretion of the drug; tumors increased in rats with larger than recommended doses for 2 y; mutagenicity has not been observed; no effect on fertility; effects on pregnancy and reproduction not known; hypocalcemia can occur in pregnancy following exposure; unknown whether alendronate enters human breast milk
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osteoporosis, low bone mass, pediatric osteoporosis, juvenile osteoporosis, fracture, compromised bone strength, osteopenia, chronic liver disease, burn injuries, Paget disease, hyperparathyroidism, hypophosphatemic metabolic bone disease, idiopathic juvenile osteoporosis, bony deformities, cardiopulmonary compromise, reduced bone density, kyphosis, kyphoscoliosis, short stature, long bone deformities, lordosis, scoliosis, pigeon breast deformity, hip fractures, inflammatory bowel disease, rheumatoid arthritis, trauma
Gordon L Klein, MD, MPH, Professor, Departments of Pediatric Gastroenterology, Hepatology, and Nutrition, University of Texas Medical Branch
Gordon L Klein, MD, MPH is a member of the following medical societies: American Academy of Pediatrics, American Gastroenterological Association, American Pediatric Society, American Society for Bone and Mineral Research, American Society for Clinical Nutrition, American Society for Nutritional Sciences, North American Society for Pediatric Gastroenterology and Nutrition, Sigma Xi, and Society for Pediatric Research
Disclosure: Nothing to disclose.
Steven M Schwarz, MD, FAAP, FACN, AGAF, Professor of Pediatrics, State University of New York, Downstate Medical Center College of Medicine; Distinguished Lecturer, New York Medical College, School of Public Health
Steven M Schwarz, MD, FAAP, FACN, AGAF is a member of the following medical societies: American Academy of Pediatrics, American College of Nutrition, American College of Physician Executives, American Gastroenterological Association, American Pediatric Society, Gastroenterology Research Group, New York Academy of Medicine, North American Society for Pediatric Gastroenterology and Nutrition, and Society for Pediatric Research
Disclosure: TAP Pharmaceuticals Honoraria Speaking and teaching; Curemark, LLC Consulting fee Board membership
Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from broker recommendation; Avanir Pharma Stock Investment from broker recommendation
Jatinder Bhatia, MBBS, Professor of Pediatrics, Chief, Section of Neonatology, Department of Pediatrics, Medical College of Georgia
Jatinder Bhatia, MBBS is a member of the following medical societies: American Academy of Pediatrics, American Association for the Advancement of Science, American Dietetic Association, American Federation for Clinical Research, American Pediatric Society, American Society for Clinical Nutrition, American Society for Parenteral and Enteral Nutrition, New York Academy of Sciences, Society for Pediatric Research, and Southern Society for Pediatric Research
Disclosure: Mead Johnson Consulting fee Consulting; Mead Johnson Honoraria Speaking and teaching; Dey LP Consulting fee Consulting; Dey LP Honoraria Speaking and teaching; Wyeth Grant/research funds Other; Med Immune Grant/research funds Other; Ovation None
Merrily P M Poth, MD, Professor, Department of Pediatrics and Neuroscience, Uniformed Services University of the Health Sciences
Merrily P M Poth, MD is a member of the following medical societies: American Academy of Pediatrics, Endocrine Society, and Lawson-Wilkins Pediatric Endocrine Society
Disclosure: Nothing to disclose.
Jatinder Bhatia, MBBS, Professor of Pediatrics, Chief, Section of Neonatology, Department of Pediatrics, Medical College of Georgia
Jatinder Bhatia, MBBS is a member of the following medical societies: American Academy of Pediatrics, American Association for the Advancement of Science, American Dietetic Association, American Federation for Clinical Research, American Pediatric Society, American Society for Clinical Nutrition, American Society for Parenteral and Enteral Nutrition, New York Academy of Sciences, Society for Pediatric Research, and Southern Society for Pediatric Research
Disclosure: Mead Johnson Consulting fee Consulting; Mead Johnson Honoraria Speaking and teaching; Dey LP Consulting fee Consulting; Dey LP Honoraria Speaking and teaching; Wyeth Grant/research funds Other; Med Immune Grant/research funds Other; Ovation None
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