376 VIII. CHOLESTEROL AND RELATED STEROLS 



have been recorded in rats,^^^ rabbits/^* and in the dog.^*^'^'*'^ In the latter 

 case, the effect was shown to be counteracted by the administration of 

 thyroxine^*" or by hypophysectomy.^^^ Hypercholesterolemia has like- 

 wise been demonstrated after thyroidectomy in horses, ^^^ as well as after 

 subtotal thyroidectomy in man.^^^ 



When the thyroid gland is non-functional, a similar trend to increased 

 blood cholesterol levels may be noted. Handler'^^ observed a hypercholes- 

 terolemia in rats following treatment with thiouracil, although the level 

 was somewhat decreased in choline-deficient rats. A higher than normal 

 blood cholesterol level was observed by Westra and Kunde'^- in cretin rab- 

 bits; the figure could be somewhat reduced by feeding thyroid tissue. 

 Human cretins likewise present hypercholesterolemia.^^^ Several investi- 

 gators^*"*"^^^ have also proved that blood cholesterol is increased in func- 

 tional hypothyroidism, including myxedema. 



In sharp contrast to the above results, increased thyroid activity re- 

 duces blood cholesterol. Thus, low blood cholesterol levels, as well as low 

 blood phosphatides, have been recorded in patients ha\'ing exophthalmic 



goiter (Basedow's disease, or Graves' disease) or other forms of hyperthy- 

 roidism, ^^^-iso 



The thyroid secretion not only controls the absolute amount of blood 

 cholesterol, but it also exerts some control over the proportion of free to 

 esterified cholesterol present in the serum. Although the ratio of free to 

 esterified cholesterol was found to be especially high in cases of hypofunc- 

 tion of the organ resulting in cretmism in children, ^^^ a normal cholesterol 

 partition has usually been noted in myxedema or other thyroid disturbances 

 in adults. ^^2 In hyperthyroidism, the ratio of free to total cholesterol in- 

 creases; the decrease in blood cholesterol is largely in the ester fraction. ^^^ 



1" P. Handler, /. Biol. Chem., 173, 295-303 (1948). 



138 w. Fleischmann, H. B. Shumacker, Jr., and L. Wilkins, Am. J. Physiol., 131, 317- 

 324(1940). 



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



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



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



'" J. J. Westra and M. M. Kunde, Am. J. Physiol, 103, 1-4 (1933). 



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



1*' L. M. Hurxthal, Arch. Internal Med., 51, 22-32 (1933); 53, 762-781 (1934). 



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



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



1" H. J. Bing and H. Heckscher, Biochem. Z., 158, 403-416 (1925). 



1^8 L. M. Hurxthal, Arch. Internal Med., 52, 86-95 (1933). 



i« E. B. Man, E. F. Gildea, and J. P. Peters, /. Clin. Endocrinol, 19, 43-59 (1950). 



160 E. G. Nicholls and W. A. Perlzweig, J. Clin. Invest., 5, 195-204 (1928). 



1" H. Schwarz and A. Topper, /. Pedial, 3, 242-246 (1933). 



'" J. P. Peters and E. B. Man, /. Clin. Invest., 22, 715-720 (1943). 



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



