Definition. A non-inflammatory enlargement of the thyroid gland, independent of known microbes or parasitism.
Causes. Goitre is an endemic disorder in man and beast, though it may occur sporadically during or after a debilitating disease, or in animals that are overworked or out of condition. As occurring endemically all accessory factors that undermine the general health must be admitted as potent factors, though insufficient of themselves to develop the malady in the absence of the specific cause. Thus in Europe women suffer more than man, being more confined indoors and being less muscular and vigorous. In New York the new born offspring of ewes, kept in close confinement during winter, may be all goitrous, while those of flocks, having a free run through the whole season, escape. Gurlt has seen the same in goats. Apart from debilitating diseases New York horses and cattle develop the greater number of cases in winter, the period of confinement and idleness. House dogs suffer more than hounds.
Poor diet has a similar effect. In Europe where the disease is very prevalent in the underfed peasant population, it is rare among the highly fed domestic animals. Bouley says it is excessively rare in animals even in the localities in which it prevails in man, and though mentioned by Lydtin, Johné, Haubner and others it is not as a common affection. In New York and Pennsylvania on the other hand it is rare in the well-fed human population, and very common in horses, mules, cattle, sheep, swine and dogs. I have known congenital goitre to prove fatal to a new born dromedary in Central Park, New York. The long, severe winter, close confinement, and impure air, doubtless as much as the spare diet contribute to this prevalence among the animals in New York.
Intestinal worms and other parasitisms must be accepted as secondary factors, the development of goitre often going on simultaneously with the increase of the parasites.
Heredity is claimed as a cause by Möller and others, and doubtless a weak constitution transmitted from parent to offspring, is more susceptible. Apart from this the exposure of both to a common specific cause is the main factor in its production.
Locality. This must be accorded a first position in the causation of goitre, so far at least as it occurs endemically and enzootically. In England it has prevailed, in man, on the limestone hills of Derbyshire, and Gloucester (Cotswold); in Europe it is common in the Alps, Pyrenees, Savoy, Styria, Silesia, in the Black Forest and in the Rhone valley; in Asia it prevails in the Himalayas, the Altai Mountains, the hills of China, and in the Punjaub; in South America it is seen in the valley of the Oronoco; in North America in Saskatchewan, Ontario, Michigan, Ohio, Pennsylvania, New York, Vermont, Virginia and Alabama. A large number of these localities lie on magnesian limestone or are supplied with water that has percolated through this, so that at one time the excess of magnesia and the lack of iodine were held to be the main causative factors. This contention cannot be sustained in all cases, so that the disposition is, at present, to attribute the disease to some unknown poison. This unknown poison may be present in districts apart from the magnesian limestone, yet the disease is so frequently seen upon this formation that its presence must always be looked upon with suspicion as a probable bearer of the poison, and waters bearing its products are unsuited to the victims of goitre.
Pathological Anatomy. Sometimes the swelling of the gland which appears during catarrh or pharyngitis will subside on recovery. In other cases it remains as a distinct hypertrophy. This is usually an increase of the parenchyma and dilatation of its follicles with an albuminous fluid (hypertrophic goitre). This may affect one lateral lobe or both. In other cases the fibrous tissue mainly increases and the gland becomes hard and resistant (fibrous goitre). In other cases the individual follicles become distended, and may even break into each other forming a large cavity or several with liquid contents (cystic goitre). In other cases there is a great increase of the vascular network of the gland so that blood alone is obtained on puncture (varicose goitre). Tumors of all kinds may be found in the gland, thus encysted adenoma, sarcoma and melanoma in horses, carcinoma in old dogs.
Symptoms. In horses there may be swelling of one lateral lobe of the gland or of both, reaching individually the size of a hen’s egg or the fist, or larger. Cadeac cites cases that weighed 4 lbs. In dogs, cattle, sheep and especially in swine, the two lobes are much more closely connected, and the disease affecting both, together with the commissure, the whole may be resolved into one uniform swelling, much larger than in the horse relatively to the size of the animal, often covering the whole front of the neck, and extending into the chest. Cadeac mentions cases in the dog in which the mass weighed 4 lbs.
The smaller swellings appear in the solipeds on the two sides of the larynx, and in other animals more in front. They are mobile, but rise somewhat with the larynx in swallowing, and are usually covered by loose, movable skin. The consistency of the swelling varies; some are soft, elastic or pitting on pressure, others fluctuate and still others are firm and resistant. Old cases that have become calcified may even feel bony. In dogs it will sometimes pulsate like an aneurism.
Functional secondary troubles are rare in solipeds. In the other animals the goitre may compress the pharynx or gullet causing dysphagia, or the larynx, trachea or recurrent nerves causing more or less wheezing or dyspnœa. Asphyxia is not uncommon in new born sheep, and goats, and Johné and the present writer have seen cases in dromedaries. The soft embryonic tracheal rings had been so compressed from side to side that respiration became impossible. Honert records a case of asphyxia in an adult horse. Cases of roaring in adult horses and mules and of asphyxia in adult dogs are also on record. Warz records the obliteration of the jugular in a dog, and Cadeac œdema of the lips and face.