Clinical use of bone densitometry

Non-invasive densitometry

Several non-invasive methods are available to measure bone density in different regions of the skeleton. Bedrest and microgravity both lead to bone loss, which is more marked in the lower parts of the skeleton. The bone loss can be monitored by non-invasive techniques in longitudinal studies when precision (i.e. the ability to produce repeated measurements with the same value) is adequate. Bone mineral density (BMD) can be measured with single photon absorptiometry in the lower forearm and calcaneus and with dual energy X-ray absorptiometry (DXA) in almost any region of the skeleton. The latter technique pairs good precision with very low radiation exposure. With peripheral quantitative computed tomography very precise measurements of the lower forearm and tibia are feasible with low radiation dose. It has the additional option of separate measurement of cortical and trabecular bone. This could be of particular importance in microgravity studies, as trabecular bone loss is more severe in this condition. A new development is the measurement of ultrasound velocity or attenuation which depends on bone density and structure. Ultrasound data of the calcaneus correlate well with bone mineral density in spine and hip. The advantage of this technique is that it operates without radiation. However, the clinical value has to be established. The ultimate choice of technique and skeletal region for bone densitometry will depend on specific requirements.

Monitoring for adverse effects from systemic drugs used in dermatology

Systemic drugs with an associated element of risk are essential in managing many important dermatoses. This review identifies eight major drugs or drug groups used in dermatology that require systematic monitoring for adverse effects. The complete monitoring process is emphasized, including significant patient involvement in reporting key signs or symptoms that allow early diagnosis of many of these adverse effects. The concepts of "risk-risk" assessment and "critical toxicities" are defined, emphasizing their important role in maximizing drug benefits and safety. Drug-related risk factors, disease-specific risk factors, and patient characteristics or habits that increase the risks from systemic drugs are identified. Basic principles of monitoring for adverse effects, specific clinical features of the most important adverse effects, along with detailed monitoring guidelines for methotrexate, retinoids, dapsone, corticosteroids, and cyclosporine are presented.

Osteopenia in men with a history of delayed puberty

BACKGROUND AND METHODS

The effect of delayed puberty on peak bone mineral density in men is unknown. To determine whether such a delay reduces normal peak bone density and leads to osteopenia during adulthood, we measured radial bone mineral density by single-photon absorptiometry and spinal bone mineral density by dual-energy x-ray absorptiometry in 23 men who had a history of constitutionally delayed puberty and 21 men who underwent normal puberty. Their mean ages were 26 and 24 years, respectively. The groups were matched for other factors known to affect bone mass.

RESULTS

The mean (+/- SD) radial bone mineral density was significantly lower in the men with a history of delayed puberty than in the normal men (0.73 +/- 0.07 vs. 0.80 +/- 0.05 g per square centimeter; P less than 0.0002). Spinal bone mineral density was also significantly lower in the men with delayed puberty than in the normal men (1.03 +/- 0.10 vs. 1.13 +/- 0.11 g per square centimeter; P less than 0.003). Radial bone density was at least 1 SD below the mean value for the normal men in 15 of the 23 men with a history of delayed puberty, and spinal bone density was similarly decreased in 10 of the 23.

CONCLUSIONS

Adult men with a history of constitutionally delayed puberty have decreased radial and spinal bone mineral density. These findings suggest that the timing of puberty is an important determinant of peak bone density in men. Because the peak bone mineral density achieved during young adulthood is a major determinant of bone density in later life, men in whom puberty was delayed may be at increased risk for osteoporotic fractures when they are older.

Intranasal salmon calcitonin. A review of its pharmacological properties and potential utility in metabolic bone disorders associated with aging

Salmon calcitonin, a polypeptide hormone secreted by the parafollicular C cells of the thyroid gland, lowers serum calcium levels by decreasing bone resorption and renal tubular calcium reabsorption. An analgesic action, possibly mediated via beta-endorphins, is also evident. In the past, parenteral formulations of salmon calcitonin have been used in the management of metabolic bone disorders, but their routine use has been limited by the inconvenience of this route of administration and by poor tolerability. The development of an intranasal preparation of salmon calcitonin will provide a more convenient means of administering the drug. In clinical trials published to date intranasal salmon calcitonin has been effective and well tolerated in small numbers of recently postmenopausal women at risk of developing osteoporosis, and in patients with established osteoporosis, Paget's disease, or osteoporosis secondary to corticosteroid usage, multiple myeloma or ovariectomy. For periods of up to 2 years the drug reduces bone resorption and improves bone architecture, relieves pain and increases functional status. Further research is needed to confirm longer term efficacy (in particular, effects on fracture rate), optimal dosage schedules and the role of intermittent and combination treatment regimens.