NONINVAS i VE ANALYSIS OF BONE MINERAL CONTENT

Several pathological condit ions i n which bone mineral izat ion i s deficient have been observed. These can a r i s e from a number of conditions including abnormali t ies i n hormonal regulat ion, r e n a l cor t ical damage and lack of adequa te calcium and vitamin D in the die t . Osteoporosis, t he most common condition, i s associated with aging in both sexes and with alterations in hormonal regulation during menopause. In general terms, onset of the condition may involve a series of events that begin at the age when bone mass ceases to increase [i.e., about 30-40 years]. A number of factors may be involved, including regulation of calcitonin, parathormone, and 1,25dihydroxyvitamin D levels. The lahydroxylase activity of the kidney that is involved in conversion of vitamin D to its active form may decrease as part of the aging process and/or in response to lower secretion of estrogen. The resulting decrease in intestinal absorption of calcium places an increased demand on the skeletal system. The mineral content of skeletal tissue decreases, especially in trabecular bone (i.e., bone of the type found in the spine, hip, wrist and heel), and there is a subsequent increase in the incidence of fractures. The ske le ta l complications of osteoporosis become apparent in women as early as 40-50 years of age, but somewhat later in men. Fractures of the hip can be life-threatening in the aged, and the annual cost associated with them is more than 3 billion dollars in the United States alone. There is at the present time a clinical need for a rapid assay of the mineral content of bone. Procedures that require the taking of a bone biopsy sample are very painful and distressing to the patient, and the risk of infection is high. A more desirable approach would be to perform a noninvasive assay of the bone while it is still in the patient. The best procedures available at the present time are dual-photon absorptiometry and quantitative computed tomography (1). There is some question, however, of whether routine screening of healthy women of child-bearing age should be done with ionizing radiation. In this work, we demonstrate the feasibility of quantifying the mineral content of a stationary sample of bone with 31p NMR spectroscopy. These experiments differ from previous reports (2-7) in that cross polarization pP), magic angle sample spinning (MAS) and proton decoupling, which cannot be applied readily to a clinical assay, are not used. Instrumentation such as that in Figure 1 is considered.