FACTORS ALTERING CONCENTRATION OF BLOOD LIPIDS 437 



takes place. On the other hand, when the thyroid gland is extirpated, or 

 when its rate of secretion is at a low level, all blood lipids tend to be in- 

 creased considerably above their normal values. Although all of the sev- 

 eral lipid fractions of blood are affected by variations in the thyroid secre- 

 tion, the most striking effects are usually to be noted in the cholesterol 

 fraction. 



a'. Serum Cholesterol and Thyroid Secretion: A number of workers 

 reported high cholesterol levels following removal of the thyroid gland. 

 Fleischmann et al. m found an increase in blood cholesterol after thyroid- 

 ectomy in rabbits ; Handler 498 confirmed this finding in rats, while Thomp- 

 son and Long, 499 and Schmidt and Hughes, 500 noted a similar result in the 

 dog. In the latter instance, the hypercholesterolemia was cleared up by 

 the administration of thyroxine, 500 or by hypophysectomy. 499 High blood 

 cholesterol values have also been reported in thyroidectomized horses, 501 

 and after subtotal thyroidectomy in man. 501 Boyd and Connell 502 reported 

 that cholesterol and, in fact, all blood lipids, increased following the 

 operation. 



High blood cholesterol values have also been noted in cases in which the 

 gland is non-functional, as well as after its surgical removal. Thus, 

 hypercholesterolemia occurs in rats treated with thiouracil, 498 but the in- 

 creased level was found to be somewhat reduced in choline-deficient ani- 

 mals. Westra and Kunde 503 observed a high blood cholesterol in cretin 

 rabbits; the figure was somewhat reduced when thyroid tissue was fed. 

 Heckscher 504 also reported a hypercholesterolemia in human cretins. In 

 addition to these findings, a number of investigators 505-508 reported high 

 blood cholesterol values in myxedema and in other forms of hypothyroidism 

 in man. The serum phosphatides and fatty acids are also increased in 

 these conditions. 508 



Foldes and Murphy 200 noted that the ratios of cell cholesterol/plasma 

 cholesterol and of cell P/plasma P were significantly decreased in hypo- 



497 W. Fleischmann, H. B. Shumacker, Jr., and L. Wilkins, Am. J. Physiol., 181, 

 317-324 (1940). 



498 P. Handler, J. Biol. Chem., 173, 295-303 (1948). 



499 K. W. Thompson and C. N. H. Long, Endocrinology, 28, 715-722 (1941). 



600 L. H. Schmidt and H. B. Hughes, Endocrinology, 22, 475-482 (1938). 



601 H. Heckscher, Biochem. Z., 158, 417-421 (1925). 



602 E. M. Boyd and W. F. Connell, Quart. J. Med., n.s. 5, 455-460 (1936). 



603 J. J. Westra and M. M. Kunde, Am. J. Physiol, 108, 1-4 (1933). 



604 H. Heckscher, Biochem. Z., 158, 422-427 (1925). 



606 L. M. Hurxthal, Arch. Internal Med., 51, 22-32 (1933). 



606 L. M. Hurxthal, Arch. Internal Med., 53, 762-781 (1934). 



607 L. M. Hurxthal and H. N. Simpson, /. Clin. Endocrinol, 1, 450-452 (1941). 



608 E. F. Gildea, E. B. Man, and J. P. Peters, /. Clin. Invest, 18, 739-755 (1939). 



