Although the condition called hyperthyroidism, which is due to excessive action of the thyroid gland, was first observed around 1830, a really complete understanding of the condition did not develop until 1890. Excessive action of the thyroid may occur at any age. The condition is much more, frequent in women than in men. In areas in which goiter is infrequent, women may have excessive action of the thyroid gland in a proportion of four women to one man.
The exact cause of excessive action of the thyroid gland is not known, but the most frequently accepted view at this time is that the body responds to stress, either emotional, physical, or infectious, by excessive action of the pituitary gland which in turn over stimulates the thyroid gland. If this condition goes on, such symptoms may develop as bulging of the eyes, which is a part of exophthalmic goiter; and there may be enlargement of the thyroid gland, although there are cases in which the thyroid gland is enlarged without other symptoms. The person who is over stimulated by thyroid is nervous, irritable and emotionally unstable. He perspires a great deal. Frequently shortness of breath and palpitation occur because of over stimulation of the heart. In every such case the doctor will want to watch the heart carefully. The basal metabolism test usually shows excess consumption of oxygen and is not specifically a test of the function of the thyroid gland. There are other conditions which can cause excess consumption of oxygen besides overactivity of the thyroid. The doctor who finds that a patient has a large excess of thyroid action will want therefore to make other tests, as of the pulse and the temperature, the manner in which the body uses iodine, and the response of the body to the taking of iodine.
Since excessive action of the thyroid is due to secretion of too much hormone or glandular substance, treatment of the condition includes a number of different procedures. The certain method is removal of a portion of the thyroid gland by surgery, with or without the use of such drugs as propylthiouracil which diminish thyroid activity. In some cases, combined with the propylthiouracil is the giving of iodine, which has an antithyroid action.
Radioiodine, which is a radioactive form of this substance, is now used to treat excessive action of the thyroid gland. Formerly similar effects were secured by the use of the X-ray but the use of radioactive iodine is now considered to be far preferable by most experts.
In some cases excessive action of the thyroid may be so great that serious symptoms develop, including fever, an exceedingly rapid beating of the heart and even prostration. Obviously, this condition is so serious that the patient should be under the immediate care of a doctor, since he may require oxygen and prompt treatment to control the heart and the fever.
The bulging of the eye in exophthalmic goiter, or as it is now preferably called, thyrotoxic exophthalmos, is a condition which can be controlled somewhat if recognized promptly, but not so much can be done if the person waits until permanent changes have taken place in the tissue around the eye. The bulging may disappear promptly following treatment of the excessive action of the thyroid. In other instances, the condition may be so severe that surgery is necessary to decompress the tissue around the eye.