A lot of people get Hashimoto's confused with hypothyroidism, or Grave's disease. I copied the following information and a link to the page it is from below:
Hashimoto's disease is a disease, and hypothyroidism is a condition. Hypothyroidism is most commonly caused by Hashimoto's disease, but the two terms are not interchangeable.
Hashimoto's disease, sometimes known as Hashimoto's thyroiditis, autoimmune thyroiditis, or chronic lymphocytic thyroiditis, is an autoimmune disease. In Hashimoto's, antibodies react against proteins in the thyroid gland, causing gradual destruction of the gland itself, and making the gland unable to produce the thyroid hormones the body needs.
Hashimoto's typically involves a slow but steady destruction of the gland that eventually results in the thyroid's inability to produce sufficient thyroid hormone -- the condition known as hypothyroidism. Along the way, however, there can be periods where the thyroid sputters back to life, even causing temporary hyperthyroidism, then a return to hypothyroidism. This cycling back and forth between hypothyroidism and hyperthyroidism is characteristic of Hashimoto's disease. So, for example, periods of anxiety/insomnia/diarrhea/weight loss may be followed by periods of depression/fatigue/constipation/weight gain.
Thyroid nodules are very common. A nodule is a swelling or lump, which can be a solid or liquid filled cyst or mass. Most are benign, but a small percentage can be cancerous. So you should always have a nodule evaluated by your physician as soon as you notice it. An estimated one in 12 to 15 women and one in 50 men has a thyroid nodule More than 90 percent of all thyroid nodules are not cancerous.
A nodule is more likely to be cancerous if it falls into certain risk factors:
Larger nodules - over 4 centimeters, are more likely to be cancerous than nodules less than 4 centimeters
- Men's nodules are more likely to be cancerous than women's nodules
- A solitary nodule is more likely to be cancerous than nodules found in a "multinodular" thyroid
- Nodules in a person younger than 20 or older than 70
- History of external neck irradiation during childhood
- "Cold" characterization on ultrasound - meaning that the nodule does not absorb iodine or make thyroid hormone
Determining which nodules are cancerous is a challenge that typically falls to endocrinologists. Endocrinologists typically evaluate nodules with radioactiove uptake scans, ultrasound, and blood tests.
Those nodules that remain suspicious are evaluated by a procedure known as fine-needle aspiration (FNA) biopsy.