Active Principles of Thyroid. — It is quite clear that the thyroid gland is es pecially characterized by the presence of a compound proteid of peculiar consti tution, and that this substance, which Robert Hutchinson calls "colloid matter," is the active constituent of the gland There is also present another proteid, nucleo-albumin, in small amount, which Hutchinson considers as probably con tained in the cells of the acini. In addition there are certain extractives to be found,—viz., xanthin, hypoxanthin, inosite, volatile fatty acids, paralactic acid, succinic acid, and calcium oxalate, —bodies, however, of no special physio logical significance. (R. II. Chittenden.) Iodine has recently been shown by Baumann to be a normal constituent of the thyroid gland. Thyro-iodine the name given by him to the product obtained—contains over 9 per cent. of iodine, and it becomes inert when the latter agent is removed from it. Bau mann has also shown that the amount of iodine in the gland is much greater when the organ is normal than when it is goitrous.
Thyro-iodine is best prepared by treat ing the gland with a solution of sodium chloride. The globulin is precipitated by a current of carbonic acid, and the solu tion acidified and boiled, when a pre cipitate of albumin and thyro-iodine falls. The latter is an organic substance combined with nitrogen and iodine (10 per cent.). Clinical observations show that thyro-iodine is very active, patients suffering from goitre and myxcedema having been cured by it. Baumann main tains that the entire active substance re mains on the filter after coagulation of the albumin. Baumann (Zeit. f. physiol. Chem., B. 21. pp. 319 and 4S1, '90).
The colloid material, believed by Hutchinson to be the active ingredient of the thyroid gland, has been found to contain iodine in organic combination, the colloid matter owing its activity to the presence of this organic compound of iodine.
The proteids of the gland are two in number: 1. A nucleo-albumin present in small amount and probably derived from the cells lining the acini. 2. The colloid matter, made up of a proteid and a non-proteid part, the latter containing, in all probability, Baninann's throidin. Certain extractives are also obtained from the gland. as creatin, xanthin, etc., which have been found absolutely inert when administered either to healthy persons or to eases of myxcedema. The same result obtained on giving the nu cleo-albumin. The pure colloid matter gave the ordinary signs of thyroid ac tivity in healthy individuals, and in large closes distinct thyroidism resulted. Marked beneficial results were obtained on administering it to a patient with myxcedema. The proteid and the non
proteid constituents of the colloid were then given separately, and although benefit resulted from the former, yet the most favorable results were obtained from the administration of the latter. Robert Hutchinson (Brit. Med. Jour., Jan. 23, '97).
The colloid substance is the active se cretion of the thyroid gland, and is made up of thyreoglobulin and nucleoproteid. Experiments were undertaken to show the influence which thyreoglobnlin and nucleoproteid exercised upon general metabolism. Results showed that in the case of dogs the excretion of nitrogen was considerably increased when thyreo globulin was given, whereas nucleopro teid had no effect upon the output of nitrogen.
Thyreoglobulin is the most active body in the thyroid gland; it contains all the iodine, and the amount of iodine in creases pari passe with the increased col loid material; it therefore follows that thyreoglobnlin is contained in the col loid material. Oswald (Troppe-Seyler's Zeit. f. physiol. Chemie. vol. xxvii, Parts I and 2, '99).
Thyro-antitoxin is the provisional name of another active principle, oh tamed by Fraenkel, from the thyroid gland of the sheep. It exerts no influ ence on nutrition comparable with that of fresh thyroid or thyro-iodine.
The albuminous bodies were precipi tated by acetic acid, and by feeding ex periments it was ascertained that the precipitate had no marked effect, while the filtrate that was obtained possessed the well-known properties of the thyroid gland, or, in other words, contained the physiological active principle. Fraenkel (Wiener med. Bl., S. 4S, '95).
In the tetanic condition toxins are found in the blood which are rendered innocuous by the thyro-antitoxin of Fraenkel, formed in the gland-alveoli. In the niyxmdcmatous condition, on the con trary, a "thyroproteid" is formed in the tissues, passes into the blood, and is fixed by the thyroid. Here it is ren dered innocuous by an enzyme which splits it up into two parts: a proteid constituent, which unites with thyro iodine, and the other a carbohydrate. Notkin (Virchow's Archiv, Suppl., B. 144, '96).
Preparations. — The implantation of a portion of the thyroid gland beneath the skin was soon superseded by the hypo dermic method, but the latter presented another drawback, that of requiring the constant attendance of the physician. Besides this the preparations often pro duced suppuration. The gland itself, therefore, administered in the form of desiccated powder in tablets or capsules, is preferred by the majority of practi tioners.