A thyroid nodule is a growth (lump) in the thyroid gland. The thyroid gland is located at the base of the neck.

Thyroid nodules are growths of cells in the thyroid gland. These growths can be noncancerous (benign) or cancerous (malignant). Some nodules are fluid-filled (cysts), while others are made of thyroid gland cells. Sometimes, what feels like one nodule will actually be a collection of small nodules.

Thyroid nodules are more common in women than in men. A person's chance of a thyroid nodule increases with age.

Only a few thyroid nodules are cancerous. (See: Thyroid cancer)

The following characteristics increase the chances that a thyroid nodule is cancerous:

• A hard nodule
• A nodule that is stuck to nearby structures
• Family history of multiple endocrine neoplasia type II
• Family history of thyroid cancer, especially medullary thyroid carcinoma
• Hoarse voice due to vocal cord paralysis
• Age -- younger than 20 years or older than 70
• History of radiation exposure to the head or neck
• Male gender

Causes of thyroid nodules are not always found, but can include:

• Hashimoto's disease
• Iodine deficiency