Faculty Bibliography

To ascertain whether exercise could prevent involutional bone loss, we studied 18 postmenopausal women, half of whom exercised for 1 h three times a week. Total and regional bone mass were measured before and after 1 year of exercise by the techniques of total-body neutron activation analysis (total body calcium) and photon absorptiometry (bone mineral content) of the distal radius. Total body potassium was measured by whole body counting. Bone mineral content and total body potassium did not change significantly in either group. Total body calcium increased in the exercise group from 781 +/- 95 g of 801 +/- 118 g (SD). In contrast, total body calcium decreased in each subject in the sedentary group. The daily calcium balance derived from the difference in total body calcium measurements was significantly different in the two groups of women (P less than 0.001). These data support the hypothesis that exercise can modify involutional bone loss.

Total and nondialyzable hydroxyproline excretion was measured in 59 postmenopausal women and 68 women with spinal osteoporosis. Hydroxyproline excretion was similar in both groups of women and the hypothesis that hydroxyproline excretion is normally distributed could not be rejected for either group. No relationship was found between hydroxyproline excretion (total and percentage of nondialyzable) and body weight, height, body surface area, or total body calcium or bone mineral content of the radius, or these latter values normalized for age, sex, and body size. There was no difference in hydroxyproline excretion in osteoporotic women who took supplemental calcium as compared to those that did not. These data fail to provide any evidence that bone turnover in osteoporotic women differs from that in younger postmenopausal women, or that osteoporosis arises from a subpopulation of women with rapid bone loss.

The techniques of photon absorptiometry of the radius and total body neutron activation analysis were used for the determination of bone mineral content and total body calcium, respectively. The subjects consisted of 71 normal women who were 1-5 yr postmenopausal and 44 osteoporotic women who had crush fractures of the dorsal spine. Both bone mineral content and total body calcium were corrected for age and body size by using the ratio of observed values to those predicted from previously derived equations. Discrimant analysis involving both osteoporotic and normal postmenopausal women resulted in the successful assignment of 81% of the 115 subjects to their correct group. Statistical analyses of the distribution of the bone mass of the postmenopausal women yielded no evidence to support the hypothesis that a subgroup exists with bone mass levels markedly different from the remainder of the women.

Serum somatomedin activity of rats was measured under several dietary conditions by 35S incorporation into chick embryo pelvic rudiment. The mean (+/- SD) serum somatomedin activity (U/ml) was reduced following 3 days of fasting (0.41 +/- 0.12) and increased to prefasting levels in animals fed a balanced diet (0.95 +/- 0.11) for 2 days. The increase in mean somatomedin activity following 2 days of refeeding a high-protein diet (0.79 +/- 0.09) was greater than that observed with a high-carbohydrate (0.56 +/- 0.10) or a high-fat (0.60 +/- 0.10) diet, but the level was not completely restored to normal. The data confirm the previous finding that fasting reduces serum somatomedin activity and suggest that the protein content of the diet plays a major role in the restoration of serum somatomedin activity following refeeding.

Endocrine evaluation is reported in 8 acromegalic patients who received 5,500 rad to the pituitary from a linear accelerator. There was a mean decrease in hGH levels of 72%. Plasma testosterone levels were low in 1 of the 6 male patients prior to pituitary irradiation and were below normal in all male patients on the final evaluation (3.1 +/- 0.2 SD years postirradiation). Deficiency of TSH secretion developed in 2 patients following irradiation. This rather high incidence of postirradiation partial hypopituitarism was not anticipated, and is thought to be related to radiation necrosis of the normal pituitary tissue which surrounds the adenoma.