those maintaining weight, but the extent of the 

 weight loss before sacrifice seemed to have no 

 influence on the size of this gland. On SP 8 

 HVO diet, thyroids were similar in size to those 

 observed in rats maintaining weight when the 

 loss in body weight was less than 100 grams but 

 were larger when the loss exceeded 100 grams. 

 On SPE diet, a high proportion of the thyroids 

 was large, even in rats that lost less than 100 

 grams. The thyroids of rats fed SPE diet were 

 consistently larger than those from rats fed stock 

 or SP 8 HVO diets for all groups as long as com- 

 parisons were confined to animals of similar 

 age, taking into consideration extent of weight 

 loss before sacrifice. 



Thyroid weight and kidney damage. — In 

 Table 47 are summarized data relating thyroid 

 size to the histological findings in the kidneys from 



rats fed stock, SP 8 HVO, or SPE diets. Large 

 thyroids were often associated with kidneys show- 

 ing extensive damage. Even in rats that were 

 maintaining weight, thyroid weight tended to 

 parallel kidney damage. The extent and kind of 

 damage in relation to the size of this organ, how- 

 ever, was influenced by diet and extent of weight 

 loss. Calcium deposition in the kidneys, seen 

 only in moribund rats, was frequently associated 

 with enlarged thyroids. Eighty percent of the 

 rats with thyroids exceeding 30 mg. had kidneys 

 containing calcium deposits. Calcium was rarely 

 found when thyroids weighed less] than 20 mg. 

 except in moribund SPE rats that had lost more 

 than 100 grams before sacrifice. No data were 

 available to establish how much of the weight 

 recorded as thyroid was due to the parathyroid 

 gland. Results from microscopic examination of 



Table 47. — Thyroid weight in relation to extent and kind of kidney damage for rats maintaining or losing 



weight on stock, SP 8 HVO, and SPE diets 



Weight status, diet, and thyroid weight (mg.) 



Rats 



Average 

 thyroid 

 weight 



Histological ratings for kidneys 





Hyalin 



Cystic 



Glomerular 



Calcium 



Rats maintaining weight: 

 Stock: 



Less than 13.0. _ _ _ __ 



Number 

 65 

 10 

 9 



32 

 2 

 6 



13 

 16 



28 

 6 



5 

 3 

 6 



16 



4 

 8 



6 



8 



21 



22 



5 



3 

 6 



4 



7 

 9 

 7 

 6 



3 

 16 

 41 

 14 



Mg. 



10. 1 

 14. 



16. 3 



10.0 



14. 6 

 17.3 



11. 1 



14. 1 

 17.0 

 21. 6 



10.2 

 14. 6 

 18. 1 



9. 6 

 13.8 

 17.7 



11. 4 

 14.2 



17. 2 

 25.3 

 33. 7 



11. 7 

 14. 3 

 17. 1 



9.7 

 17. 2 

 23. 5 

 31.6 



9.9 

 17.8 

 24.5 

 34.6 



Score 

 0.2 

 1.2 

 1.6 



.2 



.5 



1.2 



. 8 



.9 



1. 4 



1.8 



. 2 

 1. 7 

 2.3 



. 1 

 1.0 

 1.6 



1. 2 

 1.6 

 1.7 



2. 1 

 2.6 



2.3 



2.7 

 2.0 



1. 1 



2. 2 

 2.4 

 3.2 



2.7 

 2. 6 

 2.5 

 2. 4 



Score 

 

 . 5 



.8 





 

 .5 



. 2 

 . 1 



.3 

 .3 





 .3 

 1. 5 





 



.8 



.5 



. 4 



1.0 



2.2 



3.6 



1.7 

 1.7 



2.8 



.3 

 1.3 

 2.3 



2.8 



2.3 

 3. 2 

 3.2 

 3. 1 



Score 

 



. 7 

 .8 





 

 .5 



.2 

 



.7 

 .3 





 .3 

 2.2 





 



. 4 



.5 



.2 



.6 



1.6 



2.0 



1. 7 

 2.3 

 2.8 



.3 



1. 1 

 1.6 



2.8 



1.3 

 2.0 



2. 1 

 2. 1 



Score 

 



13.0 to 14.9 . _ - 







15.0tol9.9-. ... .. 







SP 8 HVO: 



Less than 13.0. _ . _ _ 







13.0 to 14.9_._ .. ... 







15.0 to 19.9. ... . 







SPE: 



Less than 13.0 . 







13.0 to 14.9. . . . 







15.0 to 19.9. 







20.0 to 29.9 







Rats losing less than 100 grams: 

 Stock: 



Less than 13.0 .... 







13.0 to 14.9 .. 







15.0 to 19.9.. . .. _. 







SP 8 HVO: 



Less than 13.0 



o 



13.0 to 14.9... . . . . 







15.0 to 19.9 . ... 



o 



SPE: 



Less than 13.0__ ._ _ _ . 







13.0 to 14.9 







15.0 to 19.9. . . 



. 1 



20.0 to 29.9 ... 



. 8 



30. and over _ ..... 







Rats losing more than 100 grams: 

 Stock: 



Less than 13.0 . _ . 



o 



13.0 to 14.9 



o 



15.0 to 19.9 



. 5 



SP 8 HVO: 



Less than 15.0. . 



3 



15.0 to 19.9__. . . 



. 7 



20.0 to 29.9 



1. 



30.0 and over. . _ 



1. 8 



SPE: 



Less than 15.0 ______ 



2. 



15.0 to 19.9 



1. 4 



20.0 to 29.9._ ... ______ 



1. 6 



30.0 and over . _________ 



2. 3 







721-631—64- 



59 



