444 IX. CAROTENOIDS AND VITAMINS A 



decrease in the fecal excretion of carotene, was attributed by Goodwin^" 

 to a direct effect upon the carotene -> vitamin A reaction, as well as to the 

 possibility that it might exert a direct effect upon the absorption of the pro- 

 vitamin. It has been demonstrated that the thyroid does not exert any 

 effect upon the stability of carotene in the intestine. 



The interpretations of the experimental data have largely been for- 

 mulated in terms of the first hypothesis. Thus, since von Noorden,^^^ 

 in 1907, suggested that carotenemia may be associated with a metabolic 

 disorder, which was later ascribed by Anderson and Soley^^^ to an altera- 

 tion in thyroid function, a number of workers"""^" have also subscribed to 

 this theory. Several other experiments have afforded confirmation of the 

 commanding role which the thyroid plays on the carotene -*■ vitamin A 

 conversion. Thus, in the case of rabbits, xerophthalmia was noted eight 

 to twenty months after thyroidectomy. "* In the case of the goat, the caro- 

 tene content of the milk increased, concomitantly with a decrease in vita- 

 min A concentration, following the removal of the thyroid gland. "^ On the 

 other hand, in the case of the cow, increased carotene was likewise found 

 in thyroid-treated animals. This may be interpreted as due to a better 

 absorption of dietary carotene. ■*" Contrary to most opinions, von Euler 

 and Klussmann"^ claimed that thyroxine exerted an inhibitory effect upon 

 the growth promoting action of carotene. Drill and Truant^" were unable 

 to cure ocular symptoms of hypovitaminosis A in rats thyroidectomized by 

 the administration of as much as 10 jug. of (S-carotene per day. However, 

 these results are open to question, since Remington and co-workers"^ were 

 able to effect a cure under these conditions within seven to nine days, 

 with a daily dosage of only 0.6 ^g- of the provitamin. Goodwin"^ demon- 

 strated the converse of the above, namely that carotene is more effectively 

 utilized in the hyperthyroid rat than in the normal animal. 



Further confirmation of a depression of the carotene -^ vitamin A reac- 



'** C. von Noorden, Die Zuckerkrankheit, 4th ed., Hirschwald, Berlin, 1907; cited 

 by V. A. Drill, Physiol. Revs., 23, 255-379 (1943), p. 359. 



1" H. H. Anderson and M. H. Soley, Am. J. Med. Sci., 195, 313-318 (1938). 



"0 M. G. Wohn and J. B. Feldman, Endocrinology, 21^, 389-396 (1939). 



"1 R. F. Escamilla, /. Clin. Endocrinol., 2, 33-35 (1942). 



"2T. Mandelbaum, S. Candel, and S. Millman, /. Clin. Endocrinol., 2, 465-467 

 (1942). 



1" H. Wendt, Klin. Wochschr., U, 9-14 (1935). 



"^ M. M. Kunde, Proc. Soc. Exptl. Biol. Med., 23, 812 (1926). 



"s H. Fasold and E. R. Heidemann, Z. ges. exptl. Med., 92, 53-56 (1933). 



"« H. von Euler and E. Klussmann, Z. physiol. Chem., 213, 21-34 (1932). 



1" V. A. Drill and A. P. Truant, Endocrinology, 40, 259-264 (1947). 



"» R. E. Remington, P. L. Harris, and C. L. Smith, /. Nutrition, 21, 597-606 (1942). 



"9 T. W. Goodwin, Biochem. J., 43, xUu-xliv (1948). 



