70 J. JOWSEY 



method in measuring only formation and resorption and not other processes occurring 

 simultaneously in this tissue. Formation and resorption take place on the surfaces of 

 the bone and the results presented in this report are based on quantitation of the 

 length of surface undergoing either formation or resorption expressed as a percentage 

 of the total surface examined. 



Hyperparathyroidism and hypoparathyroidism 



Radiological evidence of bone disease is present only in some cases of primary 

 hyperparathyroidism; more frequently renal stones and invariably an elevated blood 

 calcium and lowered phosphorus level are the presenting features of this disorder. In 

 this communication a series of twenty-seven patients were studied of whom seven had 

 bone disease visible on x-ray while the remainder did not. Quantitative microradio- 

 graphy demonstrated that resorption is elevated in all cases, the average value for 

 this group being -1-5.7 standard deviations. Bone formation levels were normal in 

 two thirds and elevated in one third of the cases. 



It would seem, therefore, that increased resorption Is characteristic of all cases of 

 primary hyperparathyroidism and that the x-ray appearance recognises only instances 

 where resorption is extensive or has been going on for some time. The increased 

 formation in a third of the cases tends to mask any Increase In porosity of the bone 

 produced by the high level of resorption. 



Hypoparathyroidism can result from either accidental removal of the para- 

 thyroid glands in thyroidectomy or, less frequently, from idiopathic lack of function 

 of the parathyreoid tissue. The blood and urine calcium levels are low but the x-ray 

 appears normal. The five cases reported here include two surgical parathyroid- 

 ectomies and three individuals with idiopathic hypoparathyroidism. Quantitation of 

 bone formation and resorption demonstrated both to be reduced, resorption to a 

 significantly lower level with formation In the low normal range. 



Osteoporosis 



The x-ray picture of osteoporosis Is typical of an extensive loss of bone tissue 

 from the skeleton, this being particularly evident in the spine where crush fractures 

 of the vertebrae and ballooning of the intervertebral spaces follow from the loss of 

 bone. 



The diagnosis of osteoporosis in the present study has been based on the radio- 

 logical examination, the blood calcium and phosphorus levels being normal and other 

 causes of osteoporosis, such as multiple myeloma, being excluded. Direct measurements 

 of formation and resorption in seventy-two cases of idiopathic or senile osteoporosis 

 by the method of quantitative microradiography demonstrate an increase in the 

 amount of bone resorption while the level of formation falls within normal limits. It 

 appears therefore that an increase in the level of resorption Is the prime factor in the 

 loss of bone tissue in this disorder. 



Cushing's disease 



Generalised decreased density on x-ray Is found in Cushing's syndrome; prolonged 

 therapy with cortisone will also produce loss of bone mass, particularly In the spine 

 and often in a few months. The fourteen cases presented here showed osteoporosis as 



