Thyroid nodules are very common growths in the thyroid gland. They primarily affect women and occur more often as you get older. If you performed an ultrasound on every woman over 50, half of them would have a thyroid nodule!
Though the cause is unknown, nodules are often made up of thyroid cells, but can also contain fluid. Types of nodules include harmless micronodules (less than one centimeter), cysts (fluid-filled nodules), inflammatory nodules seen in thyroiditis, thyroid adenomas (benign tumors), and cancerous nodules.