HYPERVITAMINOSIS A 609 



identical with those of scurvy, ""^'^^-^ and resemble symptoms resulting 

 from underfeeding in the rat, rabbit, and guinea pigj 134-1136 ^^he ad- 

 ministration of vitamin C in doses as high as 250 mg. daily did not affect 

 the response of this gland to excessive doses of vitamin A. '"'^^ 



The thyroid gland is of especial interest because of its reputed relation- 

 ship to the metabolism of vitamin A. Although Takahashi et al.^^"'' re- 

 ported that excessive doses of vitamin A caused hypertrophy of the thyroid 

 gland, no histologic changes occurred in the gland under these condi- 

 tions. ^^^^ In fact, Wolbach^''^^ stated that the thyroid glands of rats and 

 of guinea pigs which had suffered severe skeletal changes from overdosing 

 \vith vitamin A presented essentially the same picture as did glands from 

 normal animals, insofar as colloid content, vacuolization, staining and 

 height of alveolar epithehum were concerned. No variations in the thy- 

 roid glands were evident, even when comparisons were made with sections 

 of the thyroid gland from A-avitaminotic rats. In fact, Wolbach stated 

 that "the conclusion was unavoidable that this gland is not primarily in- 

 fluenced by ^dtamin A." 



Congestion of the spleen, '^^^ hypertrophy of the islets of Langerhans in 

 the pancreas, ^^^^ and basophil hyperplasia of the anterior lobe of the pitui- 

 tary"^^ occur as a result of a vitamin A excess. Masin"^^'"^^ reported 

 that estrus was prolonged in rats by the injection of 20,000 to 37,000 I.U. 

 of vitamin A, due to the "luteinizing" effect of the vitaixiin. However, 

 when pregnant rats were subjected to a continued excess of vitamin A, the 

 litter rate was diminished (to 10%), and congenital malformations oc- 

 curred in more than 54% of the surviving young. ^^^^ Gineste'^^^ found 

 that an overdosage of vitamin A reduced the growth rate of the thymus 

 gland by 21%. This was, however, in proportion to the decrease in the 

 growth of the animal as a whole. No histologic changes were noted in the 

 thymus of the rats with hypervitaminosis A, as compared with the findings 



I'S" H. Popper, Physiol. Revs., 24, 205-224 (1944). 



i"5 H. T. Blumenthal and L. Loeb, Am. J. Pathol., 18, 615-631 (1942). 



i"6 R. Whitehead, /. Pathol. BacterioL, 54, 169-176 (1942). 



1137 H. Noetzel, Z. ges. exptl. Med., 105, 83-88 (1939). 



'13* L. Cornil, A. ChevalHer, and J. E. Paillas, Ann. anat. pathol. et anal, normale mid.- 

 chir., 16, 74-83 (1939). 



1139 L. Cornil, A. ChevalUer, J. E. Paillas, and J. Chouquet, Ann. anal, pathol. et anat. 

 normale med.-chir., 16, 83-86 (1939). 



i'"" F. Masm, Acta dent, venezolana, 1, 116-120 (1950). 



ii^i F. Masin, Acta dent, venezolana, 1, 26-29 (1950). 



11" s. Q. Cohlan, Science, 117, 535-536 (1953). 



1'" P. J. Gineste, Compt. rend. soc. Uol, 135, 974-975 (1941). 



