HYPERVITAMINOSIS A 615 



time.'i" Nieman and Klein Obbink'i"" calculate the toxic dosage for 

 children at 100,000 I.U. per day. However, Caffey"^^ ])elieves that 75,000 

 I. II. of vitamin A will bring on a hy])oi-\'itaminosis A within six months. 



(r5) The Interaction of Excess Vitamin A 

 with Other Vitamins and with Hormones 



a. Interaction with Thyroxine. The thyroid gland is intimately connected 

 with the utilization and metabolism of vitamin A. It appears to be con- 

 cerned with the transformation of carotene into vitamin A, with the storage 

 of vitamin A, as well as with the secretion of carotenoids into milk. It 

 has also been reported that an antagonism exists between excess vitamin A 

 and thyroxine in hypervitaminosis A. 



Takahashi et a/.'^"^ were the first to report that hypertrophy and hypo- 

 function of the thyroid gland occur in hypervitaminosis A. In fact, several 

 investigators successfully employed large doses of vitamin A in the treat- 

 ment of Basedow's disease"^- or of general hyperthyroidism. "'^^ Three 

 doses of 30 drops each of Vogan reduced the basal metabolism in Basedow's 

 disease to practically normal values."" Peters"^^ and Fasold and Pe- 

 ters"^' demonstrated a definite antagonism between vitamin A and thy- 

 roxine. Hypervitaminosis A could be prevented in young rats by the injec- 

 tion of thyroxine; conversely, normal growth could be maintained in hy- 

 perthyroidism by the simultaneous administration of overdoses of vitamin 

 A. According to Chevallier and Baert,"^- the basal metabolism of young 

 rats is reduced when excess vitamin A is given. It is suggested that the 

 toxicity of excessive amounts of vitamin A may be related to its antago- 

 nism toward the thyroid hormone."*'' Confirmation of the effect of large 

 doses of vitamin A on thyroxine has been adduced by examination of the 

 gland itself. Thus, a reduction in the colloid content of the acini w^as ob- 

 served by Sherwood et a/."^"* after large doses of vitamin A. The daily ad- 

 ministration of 30,000 I.U. of vitamin A caused a reduction in the weight of 

 the thyroid gland of rats, together with a reduction of the basal metabo- 

 lism.^-^ Sadhu and Truscott"*^ are of the opinion that hypervitaminosis 

 A results successively in a reduction in the breakdown of thyroxine by the 



!■" A. Masi and M. Giusti, Riv. pediat. siciliana, 2, 26&-267 (1947); Chem. Abst., 43, 

 3499 (1949). 



i'8« S. Simkins, J. Clin. Endocrinol, 7, 574-585 (1947). 



"81 H. Peters, Klin. Wochschr., 12, 1977 (1933). 



"82 A. Chevallier and H. Baert, Compt. rend. soc. biol, 116, 1037-1039 (1934). 



"8' J. Chalier and M. Jeune, Compl. rend. soc. biol, 129, 604-606 (1938). 



"8^ T. C. Sherwood, L. A. Toth, and K. Carr, Endocrinologij, 18, 254-255 (1934). 



"86 D. P. Sadhu and B. L. Truscott, Endocrinology, 43, 120-123 (1948). 



