438 VRIST, :MArDOXALD, MOSS, AND SKOOG 



It is also possible that endociinopathy initiates nonspecific degen- 

 erative changes and premature aging of bone tissue. Hyperparathy- 

 roidism has specific effects on bone and causes osteoporosis b\ 

 osteoclasis and osteoc\ tohsis, and Cu.shing's svndrome inhibits the 

 proliferation of osteoblasts and produces bone resorption without 

 osteoclasts, but these conditions may also accelerate the aging process 

 and deterioration of osteocytes. The retention of bone and control 

 of the rate of reduction of bone mass, however, could be determined 

 by an antiosteopowsis factor. This seems to be associated with such 

 phenomena as maintenance of blood flow, completion of osteons and 

 development of structural bone, androgen and protein biochemistry, 

 effects of mechanical stimuli of phvsical exercise upon bone tissue, 

 liver metabolism, and the intracellular phvsiologv of the bone cells. 

 The point of view set forth above suggests the possibilit\' that 

 treatment of osteoporosis by exercise, with improved diet and injec- 

 tions of sex hormones, may stimulate the rate of capillary circulation 

 of bone and thereby slow the process of aging of bone tissue. Meas- 

 urements of urinarv products of bone breakdown such as hydroxy- 

 proline and mucopolvsaccharides are now being made to estimate the 

 rate of aging of bone and to evaluate current methods of treatment of 

 osteoporosis. 



Summary 



1. Two cases have been added to six previously reported cases of 

 osteoporosis, investigated by metabolic balance, radioisotope, and 

 tetracvcline technics. The data suggest that the metabolic functions 

 of the skeleton are performed by the 1 per cent of the bone that is 

 reactive or exchangeable, and that this is not significantly abnormal 

 in patients with osteoporosis. The deficiency is in the malfunction 

 of the 99 per cent that is the nonreactive, nonexchangeable, stable, 

 or structural bone. 



2. Twenty-five survivors from a group of 100 previouslv reported 

 aged women (average age 85) were reexamined after 5 years. Three 

 cases had osteoporosis (as previouslv determined by collapsed ver- 

 tebrae), further fractures, and significant progress of the disease. 



