The influence of infection upon the thyroid glands has been the subject of studies by various investigators for many years. Farrant reported a marked hyperplasia of the thyroids in guinea pigs which were given minimum doses of diphtheria toxin.
Burget experimented with the injection of streptococci in the tonsils of cats but was unable to demonstrate any noticeable changes in the thyroid glands. Havies studied the influence of intestinal bacteria on the thyroid gland and recorded that exophthalmic goitre is due to the tryptophane from the intestine produced owing to the absence of indol producers.
Col and Womack reported that the iodine content of the thyroid is diminished in animals suffering from infections.
Menne and Boyden have shown that the soluble streptotoxins were capable of exciting thyroid hyperplasia and hypertrophy by direct influence as well as indirectly through intravenous injections. From the results of the above-mentioned authors we can concludethat the bacterial toxins will generally cause an increased reaction in the thyroid.
The author undertook the following experiments in order to find out the effect of soluble streptotoxin on the thyroid gland.
In the experiments, strains of streptococci obtained from various sources were used. The toxin for these experiments was obtained by the method described by Dick. The organisms were cultured in plain broth. One per cent. sterile blood was added to them. The broth cultures were incubated from 4 to 6 days. The cultures were passed through filter paper until clear then through Berkefeld N filters. Filtrates from any contaminated flasks were discarded. The filtrate was then passed through Berkefeld W filters. It was then cultured to insure sterility, and was finally stored in sterile glass bottles in the refrigerator after a drop of chloroform had been added to each. In order to observe the effects of the toxin so prepared upon the thyroid gland directly, the form of injection chosen was by way of the arterial blood of the thyroid.
The procedure was as follows.
An incision was made on the median line of the neck, and then the common right carotid artery was isolated from other tissue and clipped temporarily just above as well as belew the origin of the superior thyroid artery. As soon as the injection was made, the injected part was clipped firmly with a small pair of forceps and the clip below the origin of the vessel was released. Then the clip above the origen was released, and the wound closed and sutured. In some animals the injections were made directly into the thyroid gland.
Eleven rabbits received the injections intraarterialey and four directly into the gland.
The right lobe was removed at intervals varying from 15 to 38 hours. The left lobe was obtained after the animals were killed. The lobes were fixed in Zenker's solution, embedded in paraffin in the regular way and cut in serial sections 8 micro in thickness.
All the glands in which there was evidence of a reaction to the injected toxin were characterized by swelling of the epithelium. Hyperaemia in the interstitial tissue was also found. A minimum of hyperplasia, was seen. In several instances there were changes characterized by duplication of the epithelial layer. In the majority of cases there was seen diminution in the amaunt of colloid substances, and the colloid was pale pinkish in colour.
The blood vessels were enlarged in the interstitial tissue. In a few cases leucocytes had accumulated in the supporting stroma. Because of the technical difficulties only a single injection was made. One must therefore estimate the results on this basis and compare them with the clinical cases in which toxin has passed through the circulation over a longer period of time from some focus of infection from any part of the body.
Infections in this location may disseminate organisms to other secondary foci of infection which may serve as harbors for soluble toxin production.
View full abstract