DRIED THYROIDS 193 



any value in the treatment of myxedema and cretinism. Iodine may be 

 as effective as the thyroid gland in the treatment of simple or colloid 

 goitre, however. Iodine given as medicine or in food is capable of being 

 assimilated and stored in the thyroid gland. The dried glands of dogs 

 contain from 0.03 to 0.27 per cent of iodine; in sheep, the percentage 

 varies from 0.048 to 0.383 ; in man, from 0.03 to 0.9 per cent. 



Large doses of thyroid gland given continuously to animals over a 

 considerable period produce a fairly uniform syndrome, as follows: ane- 

 mia, emaciation, weakness (especially of the hind legs), sweating, ner- 

 vousness, tremors of the muscles and tongue, a tendency to fever, rapid 

 pulse, diuresis, exophthalmos, and dilated pupils. Many of these symp- 

 toms indicate stimulation of the sympathetic system. In exophthalmic 

 goitre of the human, where an excess of thyroid secretion enters the 

 blood, the symptoms resemble an overdose of the gland (hyperthyroid- 

 ism). 



Emaciation is due to destruction of fat and protein. Protein loss, 

 and increased nitrogen elimination in the urine, are directly dependent 

 upon the iodine content of the thyroid gland administered. In the ab- 

 sence of iodine neither occurs. Destruction of fat follows enhanced oxy- 

 gen consumption in the body owing to the action of the thyroid gland 

 (see antipyretics, p. 61). Emaciation is also due to diuresis and aug- 

 mented elimination of fluids from the system. Whether this is caused 

 by direct action of the thyroid substance on the kidneys, or otherwise, 

 is imknown. The normal function of the liver and muscles to store sugar 

 is inhibited by thyroid overdosage, and glycosuria may result. 



Rapidity of the pulse, one of the most frequent toxic symptoms fol- 

 lowing large doses of thyroid gland, may be attributed to stimulation of 

 the heart muscle or accelerators. A large dose of thyroid gland injected 

 intravenously may slow the heart from vagus stimulation. 



Thyroid feeding tends to promote the growth of normal bone 

 (Bircher) and many surgeons have found that it hastens the union of 

 fractures. 



Thyroid action may be summarized as stimulating oxidative changes 

 and metabolism, and affecting particularly the nervous system. Thyroid 

 secretion is the great metabolic stimulant in the body. Toxic doses have 

 caused a loss of half an animal's weight in 24 hours. The tissues are 

 consumed as by fire. 



Uses. — The most remarkable success which attends the use of thyroid 

 medication in cretinism and myxedema in human practice has no anal- 

 agous field in veterinary medicine. In goitre in young animal's thyroid 

 treatment may be of benefit but usually iodide of sodium or potassium 

 given internally will be found more valuable. In mild cases the applica- 

 tion of a 10 per cent ointment of iodine twice daily by friction on the 

 gland, or even the painting of tincture of iodine frequently on the gland 

 will suffice. 



Thyroid administration is also used in obesity of dogs. It is rather 

 uncertain in effect, sometimes proving successful while at other times it 

 is a failure. Thyroid gland is also indicated in rickets, osteomalacia and^ 

 in delayed union in fractures. 



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