The thyroid gland (glandula thyreoidea) is situated at the front of the throat. The thyroid cells produce hormones, mainly thyroxine (T4) and a small amount of triiodothyronine (T3). The pituitary, an endocrine gland in the brain, controls the thyroid gland and, in doing so, ensures that the hormones produced end up in the bloodstream. By way of the bloodstream, the thyroid hormones reach all of the cells in all parts of the body.

Thyroid hormone plays a role in the metabolism of virtually all bodily tissues, and it stimulates longitudinal growth of the bones. Before birth and during the first three years of life, thyroid hormone is important for the growth and development of the brain and, after that, for its function. The hormone works as a kind of gas pedal and ensures that your 'engine' runs faster or slower.

A properly functioning thyroid gland produces precisely the right amount of thyroid hormone, day and night. It also stores and secretes precisely enough of the hormone. But the thyroid does not always work as it should. For example, something may have gone wrong during the development and migration of the thyroid or with the synthesis or secretion of thyroid hormone. There may also be abnormalities in the way the thyroid gland is controlled by your brain (CH-C). If the thyroid does not function properly, you may end up with the wrong amount of thyroid hormone. If the thyroid gland works too slowly, this is referred to as hypothyroidism. If the thyroid gland is working too hard, then this is called hyperthyroidism.
If the entire thyroid gland is larger than normal, then we speak of a condition called goiter. If only a small portion of the gland is growing too quickly, then you have what is known as a nodule or node.

You can also have too little thyroid hormone because your pituitary does not function properly.

Thyroid Disorders:

Reduced Thyroid Function (hypothyroidism):

• Congenital Hypothyroidism (CH-T)
• Hashimoto's thyroiditis

Increased Thyroid Function (hyperthyreoïdie):

• Graves' Disease
• Hashitoxicosis

Deviations in size of the thyroid gland:

• Goiter
• Nodule or node in the thyroid gland

Text: Marloes Vegelin
Revision: A.S.P. van Trotsenburg
Animations: Caroline Ruigrok
Editor: Paulette Mostart