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It was agreed that bone loss in women starts at or about the menopause and proceeds at about 1%/annum In men it is slower and starts later. This loss of bone in women is associated with a steep rise in the wrist fracture rate (to about 50/10 000/annum) which does not occur in men. It was also agreed that this loss of bone is due to an increase in the rate of bone resorption rather than a fall in the rate of bone formation as Albright had originally postulated. However, there was some disagreement as to the way in which loss of estrogen causes bone resorption. Gordan thought that estrogens had an anti-catabolic effect on collagenous tissues in general and quoted reports of thin skin and reduced collagenous tissues in cases of osteoporosis. Nordin considered that bone was unduly sensitive to the action of parathyroid hormone in the absence of estrogens. Duursma thought there might be altered sensitivity of bone to growth hormone or thyroid hormone. Klotz’s view was that there might be a deficiency of calcitonin. Dequeker suggested that osteoporosis was associated with growth hormone deficiency and showed increased growth hormone levels in osteo-arthrotic patients with increased bone mass.

Some literature was available concerning BMC determination in the vertebral body by means of CT (Marschall et al., 1978; Abois et al., 1978; Laval-Jeantet et al., 1979; Mazess, 1979; Ettinger et al. 1979, Cann 1980 and Adams et al., 1980). No estimates in healthy men and women during advancing age have been presented. On ethical principles it is not possible to study a group of healthy individuals with this method.

Skeletal scintigraphy is a routine procedure in the evaluation of bone disease. One of the agents of choice is methylene diphosphonate labeled with 99mTechnetium (99mTc-MDP) (1). The uptake of 99mTechnetium at sites of active bone formation is higher in comparison with normal bone (2–7). The mechanism of uptake is still controversial (8–15).

The patient with chronic renal failure (CRF) is at considerable risk for aluminum accumulation, especially when undergoing chronic dialysis.

An X-ray transmission computed tomography system consists mainly of a gantry containing a movable yoke with a fixed X-ray source which are moving around an object to be scanned and a detector system. The detector system transmits the attenuation measurements to a computer which will reconstruct the image (note: attenuation = photo-electric absorption + compton scatter).

Osteopenia and osteoporosis have no typical complaints. Back pain is the common symptom to visit the physician. This pain is nevertheless not a direct symptom of osteoporosis. Acute pain is caused by a fracture of one of the vertebrae. Irradiation does not exist in most cases. After some weeks, as a result of inadequate use of the lumbar muscles, the acute severe pain subsides into tedious complaints of the back. During the period of acute pain the patients fix parts of the spine, which leads to overburdening and hypertonia of the muscles. Patients with severe osteoporosis and collapse of some vertebrae have complaints of pain in the region between the lower ribs and the crista iliaca. This is caused by the decreased distance between these parts of the skeleton. In order to set up a sufficient therapeutic regime, it is important to realize that pain is not a direct symptom of osteoporosis, but a result of a vertebral fracture, disuse of back muscles or decreasing distance between ribs and crista iliaca.

As stated in the Introduction (chapter 1) the word osteoporosis is often misused. In case of increased loss of bone mineral without fractures the word osteopenia has to be used. The term osteoporosis should be reserved for loss of bone mass combined with fractures. In practice both words are mixed up very easily. In this study the term osteoporosis is used in all cases of diminished bone mineral content, with and without fractures.

The subjective evaluation of a roentgenogram in order to measure the state of mineralization of the skeleton has been proven to be unreliable for a long time already (Stein, 1937). Photometry and conversion to an equivalent amount of reference material has been applied to many kinds of bone (Stein, 1937 and By water, 1948). Mainly because of the rather thin layer of soft tissue around them, the phalanges, radius and ulna have been studied (Mack et al., 1939).

In order to assess a CT density value, below which the risk of a vertebral compression fracture exists, 88 patients of table 9–1 were divided into four classes according to the X-ray appearance on lateral thoracic and lumbar spine radiographs. Four different symbolic configurations were employed representing each indidivual patient (table 12–1).

In the available literature no general opinion has been given concerning proportional differences in CT density values in subsequent lumbar vertebrae, neither in healthy people, nor in osteoporotic patients. Some authors (Cann and Genant, 1980) tend to the hypothesis that in the normal individual BMC determinations on each lumbar level may result in identical CT density values. This in contrast to the osteoporotic patient in whom CT density values on different levels may be unequal. In other words: the differences in CT density on subsequent vertebral levels might be individual dependent.

Conventional lateral spine radiographs were available from 73 patients. A spine score ≽80% indicates no osteoporosis and a score

Bone tissue can be differentiated into trabecular bone, also called spongy bone consisting of trabeculae and marrow tissue and cortex or compact bone, consisting of concentric lamellar bone. Bone contains cells, collagen fibres, mucopolysaccharides, proteins, fat and minerals (mostly Ca10 (OH)2 (PO4)6 = crystalline apatite). Four types of cells can be distinguished in bone: lining cells (flat cells along the surface of the bone), osteoblasts (which are involved in bone formation), osteoclasts (large cells which are involved in the resorption of bone) and osteocytes (located within the bone).

A group of 35 patients with osteoporosis derived from the population of 106 patients (table 9–1) has been treated with sodium fluoride. Fluoride stimulates the osteoblasts resulting in an increased production of osteoid tissue. Fluoride is also built in in the apatite crystals; these crystals are more resistant to bone mineral loss than hydroxy apatite crystals. As a consequence less calcium will be available from bone resorption and more calcium is needed in order to supply the new bone. Based on theoretical considerations and practical experiences in the University Hospital in Utrecht, sodium fluoride therapy in osteoporosis is supplemented with calcium and vitamin D (Duursma and van der Sluys, Veer, 1980,1981). After two years of therapy it can be expected, that the process of osteoporosis has stopped. An increase of BMC will occur later because sodium fluoride causes a delay in the mineralization process of osteoid tissue.

The suggestion of Albright et al.1 in 1941 that osteoporosis is associated with the post-menopausal state has been sufficiently confirmed2–5. Kinetic studies, using 47Ca and strontium, measuring the skeletal acretion rate of calcium, revealed normal values6, whereas bone resorption was increased7. Significant differences in plasma calcium and phosphate between pre-menopausal women and women after natural or artificial menopause were published by Young et al.8. Gallagher et al.9 showed a significant rise in the fasting plasma and urine calcium and phosphate levels after oophorectomy. The urinary hydroxyproline/creatinine ratio is higher in post-menopausal women than before menopause. Plasma alkaline phosphatase is known to be higher in women after the age of 5011,12.