FACTORS ALTERING CONCENTRATION OF BLOOD LIPIDS 439 



of the functioning of the thyroid gland, Hurxthal, 605 ' 511 McElroy et al., 516 

 Mason, Hunt, and Hurxthal, 516 and Gilligan et al. 517 suggested that the 

 serum cholesterol level affords a more reliable index in thyroid disorders 

 than does the basal metabolism. Thus, in hyperthyroidism, serum choles- 

 terol levels averaged 130 milligram per cent 516 ; in myxedema, the mean value 

 for serum cholesterol was 321 milligram per cent. The variations from the 

 normal are more frequently noted in cases of hypothyroidism than in hy- 

 perthyroidism. 508 ' 512 



However, differences in basal metabolism and in serum cholesterol may 

 not necessarily be associated. Thus, in undernutrition, both basal me- 

 tabolism and serum cholesterol decrease. Moreover, when dinitrophenol 

 is administered, an increased basal metabolism obtains, without a concomi- 

 tant decrease in the value of serum cholesterol. 518 Most workers, therefore, 

 do not agree that serum cholesterol values are as satisfactory an index of thy- 

 roid activity as has been claimed. 500 ' 508,512 ' 516,519 For a further discussion 

 of the topic, see Epstein and Lande. 520 



c'. Blood Phospholipids and Fats, and Thyroid Secretion: Most blood 

 lipids run parallel to cholesterol in that they are increased or decreased 

 from normal by hypothyroidism or hyperthyroidism, respectively. Blood 

 phospholipid seems best to mirror the change in blood cholesterol, while 

 the neutral fat fraction shows a somewhat less satisfactory correlation 

 with blood cholesterol. Low values for phospholipids and fats have been 

 reported in hyperthyroidism, 502 ' 510 ~ 513 while high valuesfor these components 

 have been noted in the blood of thyroidectomized horses 501 and of cretins, 504 

 as well as in several other types of hypothyroidism. 502,508 Boyd and Connell 502 

 state that the decrease in phospholipid is less than that of cholesterol in 

 hyperthyroidism, although Man et al. bU found a parallelism between blood 

 cholesterol and blood phospholipid. 



Although Boyd and Connell 502 reported that neutral fat decreases more 

 than does cholesterol in hyperthyroidism, Peters and Man 214 have not veri- 

 fied this conclusion. In fact, these workers state that neutral fat is largely 

 uninfluenced by thyroid activity. High levels of neutral fat were obtained 



515 J. S. McElroy, E. B. Schuman and J. O. Ritchey, Ann. Internal Med., 12, 106-114 

 (1938). 



516 R. L. Mason, H. M. Hunt, and L. M. Hurxthal, New England J. Med., 203, 1273- 

 1278(1930). 



617 D. R. Gilligan, M. C. Volk, D. Davis, and M. L. Blumgart, Arch. Internal Med., 

 54, 746-757 (1934). 



618 W. C. Cutting, D. A. Rytand, and M. L. Tainter, /. Clin. Invest., 13, 547-552 

 (1934). 



519 J. P. Peters and E. B. Man, /. Clin. Invest., 29, 1-11 (1950). 



520 A. A. Epstein and H. Lande, Arch. Internal Med., 30, 563-577 (1922). 



