Thyroid nodules, also called adenomas, are lumps in the thyroid. Thyroid nodules are common. About 3 to 7 percent of the population has them. They are not cancer; however, nodules may become overactive and produce too much hormone. A single overactive nodule is called a toxic adenoma.
When multiple nodules are overactive, the condition is called toxic multinodular goiter. Often found in older adults, toxic multinodular goiter can produce a large amount of excess thyroid hormone.
Thyroiditis is a term used to describe a group of conditions that cause inflammation of the thyroid gland. Several types of thyroiditis can cause an overactive thyroid
Thyroiditis does not cause the thyroid to produce excess hormones. Instead, it causes stored thyroid hormone to leak out of the inflamed gland and raise hormone levels in the blood.
Types of thyroiditis that are known overactive thyroid causes include:
- Subacute thyroiditis
- Postpartum thyroiditis
- Silent thyroiditis.
Subacute thyroiditis causes a tender, painful, enlarged thyroid gland. Healthcare providers are not sure what causes this condition, but it may be related to a viral or bacterial infection.
This type of thyroiditis usually goes away on its own in a few months. Many people with subacute thyroiditis briefly develop hypothyroidism
-- when hormone levels are too low -- after the overactive thyroid gets better but before the thyroid gland is completely healed.
About 8 percent of women who have been pregnant develop postpartum thyroiditis within a few months of giving birth. This is believed to be an autoimmune condition and causes overactive thyroid that usually lasts for one to two months.
Postpartum thyroiditis is likely to come back with future pregnancies. As with subacute thyroiditis, women with postpartum thyroiditis often develop hypothyroidism before the thyroid gland is completely healed.
In some women, the gland does not heal and hormone levels remain low. These women must take thyroid hormone replacement therapy
for the rest of their lives.