Hashimoto's thyroiditis may not cause symptoms for many years and remain undiagnosed until an enlarged thyroid gland or abnormal blood tests are discovered as part of a routine examination. When symptoms do develop, they are either related to local pressure effects in the neck caused by the goiter itself, or to the low levels of thyroid hormone. The first sign of this disease may be painless swelling in the lower front of the neck. This enlargement may eventually become easily visible. It may be associated with an uncomfortable pressure sensation in the lower neck. This pressure on surrounding structures may cause additional symptoms, including difficulty swallowing.
Although many of the features associated with thyroid hormone deficiency occur commonly in patients without thyroid disease, patients with Hashimoto's thyroiditis who develop hypothyroidism are more likely to experience the following:
- Difficulty learning
- Dry, brittle hair and nails
- Dry, itchy skin
- Puffy face
- Sore muscles
- Weight gain
- Heavy menstrual flow
- Increased frequency of miscarriages
- Increased sensitivity to many medications
The thyroid enlargement and/or hypothyroidism caused by Hashimoto's thyroiditis tends to progress in many patients, causing a slow worsening of symptoms. Therefore, patients with either of these findings should be recognized and adequately treated with thyroid hormone. Optimal treatment with thyroid hormone will eliminate any symptoms due to thyroid hormone deficiency, usually prevent further thyroid enlargement, and may sometimes cause shrinkage of an enlarged thyroid gland.
Other Associated Disorders
Although the majority of patients with Hashimoto's thyroiditis and their genetic family members will never experience any other autoimmune condition, they do have a statistically increased risk of developing the following disorders:
- Type 1 Diabetes Mellitus (insulin-requiring)
- Graves' disease (goiter and hyperthyroidism or overactive thyroid)
- Rheumatoid arthritis
- Pernicious anemia (inability to absorb vitamin B12, potentially causing anemia and neurologic problems)
- Addison's disease (adrenal failure; the adrenal gland provides cortisol to handle stress and illness)
- Premature ovarian failure (early menopause)
- Vitiligo (patchy loss of skin pigmentation)
- Thrombocytopenic purpura (bleeding disorder due to inadequate platelets in the blood)
- Lupus erythematosus (autoimmune disease that involves skin, heart, lungs, kidneys)
Hashimoto's thyroiditis results from a malfunction in the immune system. When working properly, the immune system is designed to protect the body against invaders, such as bacteria, viruses, and other foreign substances. The immune system of someone with Hashimoto's thyroiditis mistakenly recognizes normal thyroid cells as foreign tissue, and it produces antibodies that may destroy these cells.
Although various environmental factors have been studied, none have been positively proven to be the cause of Hashimoto's thyroiditis.