Osteoporosis

Stuart-Smith, Deryk Aubrey (1971) Osteoporosis. MD thesis, University of Glasgow.

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Abstract

1 The bone mass, as measured by X-ray indices or X-ray densitometry, increases up to between 25 and 40 years of age depending upon the measurement used. All measurements, except cortical density in the male, fall with increasing age thereafter. The cortical density increases throughout life in the male. The X-ray indices, S.A.E and T.C.M. show an accelerated fall after the menopause in women. The description of investigations in patients who are defined as osteoporotic should be accompanied by measurements which indicate whole bone density, total mineral per unit length of bone, and cortical density. Furthermore, these measurements must be related to the measurements in the normal population of the same age and sex. The best way to quantitate the relation between the patients studied and the normal population is to measure and report the percentile value of the measurement. This has been done in patients with fractures, backache, hyperparathyroidism, hypoparathyroidism, osteomalacia and gastric surgery. 3 Any bone mass measurement which falls with age can be correlated with fracture incidence which rises with age. However, only the total cortical mineral per unit length of bone is related to the rate of change in fracture incidence in both men and women with age, and is the measurement which will correctly define the risk of fracture in both male and female subjects. There is a very marked increase in the incidence rate of fracture after the age of 75 years in both men and women. At this time, the rate of change in bone mass is in fact decreasing. Clearly, this increase in fracture incidence after 75 years of age must be dominated by factors other than the rate of bone mineral loss. Spinal biconcavity and fracture is related to the amount of bone present and not to the percentile value relative to the normal population. 4 Though all the above-mentioned measurements are required to define the bone status, a single measurement can be used to describe a patient as being osteoporotic, but this measurement must take into account the size of the individual. A convenient measurement which fulfills this criterion is the whole bone density of the 3rd metacarpal (S.A.E.). The value of the S.A.E. which gives a useful dividing line is 28. There is a considerably higher incidence of spinal biconcavity and fracture of the femoral neck in women when the whole bone density falls below this value. This value also corresponds with the 5 percentile value at the age of 35 years, when the whole bone density is greatest for both men and women. 5 All subjects, but especially women, lose bone with age. In the absence of any predisposing factors such as gastric surgery or steatorrhoea there is evidence that there is a specific group of patients in whom the rate of bone loss is greater than in the normal population. The mean bone mass in patients with symptoms, such as backache or fracture, do not differ significantly from the normal population. Furthermore, while osteoporosis is a major problem in the elderly woman, it is of much less significance in the male. 6 The rate of bone mineral transfer in women falls with age. The urinary hydroxyproline excretion, which correlates with the rate of bone destruction, again measured with isotopes, rises with age. Though the bone mineral transfer rate does not measure the true bone formation rate quantitatively, the experimental evidence in dogs quoted in Chapter VI is that the bone mineral transfer rate correlates with the rate of bone formation. The evidence therefore is in keeping with a fall in the true bone formation rate with age and a rise in the bone destruction rate in women. However, as the bone mass falls with age, the rate of bone formation per unit mass does not change significantly. There is, however, a significant rise in the rate of bone resorption with age. 7 These studies show that the bone loss with age in women is associated with decreasing dietary intake, diminishing calcium absorption, a failure to attain a corresponding fall in urinary calcium excretion, a fall in the rate of bone formation and a rise in the rate of bone destruction with age. Normal male subjects also show a slight fall in dietary intake with age. They do not, however, show any fall in calcium absorption. (Abstract shortened by ProQuest.).

Item Type: Thesis (MD)
Qualification Level: Doctoral
Additional Information: Adviser: B EC Nordin
Keywords: Medicine
Date of Award: 1971
Depositing User: Enlighten Team
Unique ID: glathesis:1971-72923
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 Jun 2019 11:06
Last Modified: 11 Jun 2019 11:06
URI: http://theses.gla.ac.uk/id/eprint/72923

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