154 



GROWTH 



the rate of metabolism of all tissue protoplasm. In fact it is ex- 

 plained as a deamidizing agent that hastens the liberation and 

 destruction of amino acids and their excretion by the body. The 

 acceleration of oxidative and catabolic processes may sharply 

 distort the normal average body growth and form. 



Underdevelopment and hypoactivity of the thyroid is ex- 

 pressed in a very different but characteristic way on the growth 

 of certain tissues. Infantile hypothyroidism stunts growth in 



size and stature, producing 

 cretinism. A cretin is a 

 dwarf for his age. His 

 skeletal and connective tis- 

 sues do not grow in normal 

 rate. There is a marked in- 

 crease in the relative mass 

 of subdermal connective tis- 

 sues. The abdomen is pro- 

 truding. There is a fullness 

 of face, lips, nose, thicker 

 skin, and enlarged tongue 

 which in the extreme case 

 overfills the mouth. The 

 eyes are peculiar and ex- 

 pressionless, the reactions of the nervous system are sluggish 

 and imbecile in type. In short, the appearance of the ordinary 

 cretin is that of a dwarf with low mentality. 



That the cause of cretinism is due to absence of the thyroid 

 hormone is best shown by the effect of artificial thyroid feeding. 

 After a few months of thyroid feeding the skin of a cretin 

 clears and becomes thinner and more normal in texture, the 

 eyelids are thinner, the lips and tongue smaller, the activity and 

 expressions more alert. Skeletal growth is again accelerated. 

 The imbecile cretin is transformed to the alert normal child. 

 This defect of the thyroid when congenital is probably never 



Figure T). Artificial cretinism in the sheep 

 induced by surgical removal of the thyroid 

 glands in a lamb aged two months. The figure 

 shows the animal at fourteen months of age 

 in comparison with the sheep of normal size. 

 After Sutherland Simpson. By permission of 

 the Quarterly Journal of Physiology. 



