The rational hygiene of the thyroid gland consists in the avoidance of all agencies that may prove harmful to the gland, the most important of which are infectious diseases; frequent pregnancies; sexual excesses; intoxications by food, stimulants, or drugs; and emotions such as grief, sorrow, etc.

It will not be difficult to prevent some of these, but it will be nearly impossible to avoid others, such, for instance, as infectious diseases. There is not the least doubt, however, that at times we expose ourselves quite unnecessarily to infections, as when we drink water that has not been boiled or filtered, or when we take milk from uninspected dairies for a long time; or, again, when we remain too long a time in the confined air of assembly halls, etc., and breathe the air that has been exhaled by thousands of others, many of them possibly with infectious diseases of the throat and lungs. Many a case of infectious disease, with all its dangers to life or to important organs, such as the thyroid, may be avoided by proper circumspection.

It is also quite unnecessary for us to expose ourselves to the dangers arising from the decomposition of meat, which is particularly injurious, when taken in large quantities, to the thyroid, as shown by the experiments of Breisacher, Blum, Chalmers Watson, etc., more especially if animal food be taken that is not quite fresh and can cause the formation of ptomaines. According to Blum the thyroid has the special function of destroying poisons formed in the intestines, in particular by the decomposition of animal food. Now when too much work is thrown up on this important gland, it is easy to understand that after a time it will give out, and to prevent this we must avoid taking large quantities of animal food or fish (which is meat also, a fact not realized by many people), and when we do take it, we must first be certain that it is in a fresh condition. To enable us to do this we are provided with special sense-organs, and our eyes, nose, and the taste papillæ of our tongue will inform us whether the meat, and especially the fish or crustacean, is in a fit condition to be eaten.

We have mentioned several times that alcohol and tobacco, taken in large quantities or for a long time, are deleterious to the thyroid, which fact will justify our abstinence therefrom, or the greatest moderation in their employment; those who can do without stimulants will always be the best off.

Sexual excesses can also be easily avoided, and women who wish to retain their youth will do well not to expose themselves to pregnancies year after year after having had three or four children. It is, however, great good fortune to have a numerous progeny, and by careful hygiene, as plenty of instances prove, the struggle against premature old age can be carried out successfully. In regard to this we may refer to the chapters on the causes of old age and on sexual hygiene. Diseases of the ovaries must be particularly avoided, as all changes in those glands will react on the thyroid, which is closely related to them.

Doubtless one of the most difficult tasks will be the avoidance of strong emotions: grief and sorrow; and yet we are not helpless against them, as will be illustrated in the chapter on the hygiene of the mind and on the advantages of a religious belief.

Having dwelt on the necessity of preventing injury to this important gland, we will now show that there are certain means of enhancing its vitality,—which effect we can obtain by improving the circulation, and removing agencies by which this would be impaired. As Sir Herman Weber has shown, it is possible to improve the working condition of this gland by massage, which should be done daily and is readily carried out.

It is easy to see that a tight collar offers difficulty to the free circulation of the blood through this gland, and therefore it is advisable to wear a loose, and also low, one. Strange to say, many ladies wear such tight, high collars, not availing themselves of their immunity from such a yoke, which men have voluntarily endured for so long a time. It is advantageous not to button both sides of the shirt-band to which the collar-stud is fastened, but one side only, which is easily done when low collars are worn and is not noticeable; the great comfort and advantage of so doing will outweigh all other considerations.

The vitality of the thyroid gland may be enhanced by various measures in which thyroid secretion, or iodine—its main element,—is introduced into the body. The easiest way to effect this is by taking foods, such as plants and vegetables, which contain a maximum of iodine. The iodine in the thyroid and other parts of the body is introduced therein mainly with our food (or by drugs in the case of goiter). Another way is by taking thyroid extracts. Since, at a certain age,—as mentioned in the chapter on the causes of old age,—parts of the epithelium of the thyroid are degenerated and replaced by connective tissue, thyroid extracts will be the best means, if taken in very small doses, of supplying this physiological need. Such doses of the extracts, freshly prepared and from a reliable firm, can do no harm, but, on the contrary, will keep the thyroid in good working order. As we have learned from personal experience these very small doses can even be taken, at intervals, for a long time, without injury to the health, and we need not await the arrival of old age, but should use them as a preventative against it, and in particular temporarily where there is, or has been, a great demand for thyroid secretion, as, for instance, in convalescence after an infectious disease, or after childbirth, especially if the flow of milk is scanty, which is an expression of a defective thyroid; also after sexual excesses, and in cases of mental depression, after we have suffered grief; in fact, after any of the occurrences which we know to be harmful to the thyroid gland, which, in such cases, has been giving off larger amounts of its secretion.

We must, however, caution patients against ever taking these extracts save under medical advice, since otherwise dangerous results may be and have been produced, as will be shown elsewhere.

The diet of greatest hygienic value with regard to the thyroid will consist of large quantities of milk, with little or no meat, but plenty of vegetables.

With such a diet there will result less putrefaction in the intestines, and thus also less demand for the thyroid secretion to destroy poisonous matters; at the same time, along with the milk and vegetables, iodine, the main element of the thyroid secretion, will be brought into the body, and a loss of this product from it prevented.