Like the heart and other organs, the thyroid gland is the name of an organ, not the name of a disease. In the heart, diseases such as angina pectoris (severe pain in the heart) and cardiac infarction (heart attack) can occur. Likewise, in the thyroid gland, diseases particular to the thyroid gland can develop, but because more than one disease can affect the thyroid gland, having a "bad thyroid gland" does not suggest any specific disease that actually affects the body.

The characteristics of thyroid disorders

Thyroid disorders are characterized by two factors: changes in the "function" of the thyroid and changes in the "shape" of the thyroid. Some are marked by both factors, while others are marked by only one of the two factors.

Changes in the "function" of the thyroid gland

The function to produce thyroid hormones becomes abnormal, resulting in excessive or deficient thyroid hormones. This is called "abnormality of the thyroid function."

[Hyperthyroidism]

An excessive amount of thyroid hormones are produced and the rate of metabolism in the body increases excessively.

[Hypothyroidism]

Decrease of thyroid hormone synthesis causes a reduction in the rate of metabolism in the body.

Changes in the "shape" of the thyroid gland

The thyroid gland becomes swollen or a lump (nodule) develops in the thyroid gland, resulting in a morphological change of the thyroid gland itself. The swelling is called "goiter."

[Diffuse goiter]

This disorder is characterized by the enlargement of the entire thyroid gland. The shape (contour) of the thyroid gland remains the same.

	Simple diffuse goiter
	This disorder is characterized by the presence of simple diffuse goiter and the absence of abnormal hormone synthesis. Simple diffuse goiter can be a precursor symptom of Graves' disease or Hashimoto's disease.
	Graves' disease
	This disorder is characterized by the presence of thyroid-stimulating substances and the excessive synthesis of hormones. Heartbeat may become rapid or the eyes may bulge out.
	Hashimoto's disease
	This disorder is characterized by the chronic inflammation of the thyroid gland. It is also referred to as chronic thyroiditis. The hormone synthesis is normal in most cases, but the amount of synthesized hormones can decrease. Hormones may temporarily leak from the thyroid gland (painless thyroiditis).
	Subacute thyroiditis
	This disorder is characterized by the swelling of the thyroid and the occurrence of pain. Subacute thyroiditis often causes fever. As the hormones temporarily leak from the thyroid gland, it causes systemic (affecting the entire body) symptoms like in Graves' disease. Symptoms gradually disappear. Recurrence is rare.

[Nodular goiter]

This disorder is characterized by the development of a nodule in the thyroid gland.

	Neoplastic disease
	This disorder is characterized by the development of a tumor in the thyroid. No abnormal hormone synthesis occurs in most cases. The tumor may form a pouch (cyst), and retain fluid.

You can read detailed descriptions about each disorder in the respective sections. If you have any questions, please consult your doctor or use the Medical Counseling Room (in the 1st floor). Detailed booklets and books about diseases or daily lifestyle habits are also available.

About thyroid disorders and heredity

How likely is the disease to be inherited?

It is considered that genetic factors are somewhat involved in the onset of Graves' disease, Hashimoto's disease and certain thyroid tumors.
One frequently-asked question is "If a parent is affected with Graves' disease or Hashimoto's disease, how likely is the disease to develop in the child as well?" We do not have a clear answer to that question, however. It is considered that even identical twins, who share the exact same genes, have about a 35% chance of both of them being diagnosed with Graves' disease.
Accordingly, thyroid disorders are not only caused by genetic factors. It is, however, still unknown what other factors are involved. Certainly, as a parent and child do not share the exact same genes, there is less chance of the onset of Graves' disease in both of them than in identical twins.
Even if the disease is genetically transmitted, boys are less susceptible to thyroid disorders than girls.

Is the onset of thyroid disorders predictable?

No reliable prediction method is available at present. In Graves' disease or Hashimoto's disease, however, many people have an enlarged thyroid gland before the onset of the disease, which can be one of the indicative symptoms. Those who have this swelling are often likely to have one or more relatives with Graves' disease or Hashimoto's disease and if they do, the onset of the disease is more likely to occur than in others. It would be better to see a doctor for an examination once or twice a year.

When to visit the hospital for an examination

Even if a baby carries the gene for a disease, the onset of the disease can occur at various stages of life. The disease may or may not develop soon after birth. The onset of thyroid disorders occurs many years after birth in many cases and it is rare for them to develop in babies or children. Of all the patients with Graves' disease, children under the age of 15 account for only 3%. Therefore, you do not have to worry too much while your baby is little. If you are still worried, we would recommend that you take the child to the hospital when he/she is around 6 years old. Even if his/her thyroid gland is swollen, medical examination is not really necessary if your child is still little and no symptoms have appeared. As your child becomes older, an examination once a year is sufficient.
In some cases, the onset of the disease in a child is followed by the onset of the disease in his/her parents or grandparents.

Thyroid disorders are not scary

Thyroid disorders are "not scary," if you are treated by a specialist and follow the instructions given by the doctor. It is more practical to regularly receive medical examination and understand the condition of the body than to fret over the possibility that the disease might be passed on to you from your parents or that you might pass it on to your child.
Genetic factors are also considered to be involved in the onset of diseases such as high blood pressure and diabetes, but thyroid disorders are easier to treat than these ailments. It may take a while until recovery, but if you regularly see your doctor, you can get on with your life as usual and the disease will not affect other organs.

Pregnancy and delivery

If an expectant mother with a thyroid disorder is controlling her condition, her pregnancy and delivery only require the same precautions as for healthy expectant mothers. Even if you get pregnant and give birth to a baby while you are suffering from a thyroid disorder, it does not mean your disorder is more likely to be passed on to your baby.
In some cases, babies show symptoms of Graves' disease soon after birth, but the symptoms are temporary and are not caused by genetic factors. The above is what we know about the heredity of thyroid disorders at present. Progress in medical technologies and knowledge is made every day, however. We will inform you when a discovery or a breakthrough is made.