Between 10–30% of individuals with TS develop primary hypothyroidism, Hashimoto thyroiditis. Levels should be measured at the time of diagnosis and at intervals of 1–2 years thereafter.
Hashimoto’s thyroiditis (also called autoimmune or chronic lymphocytic thyroiditis) is the most common thyroid disease in the United States. It is an inherited condition that affects over 10 million Americans and is about seven times more common in women than in men.
Hashimoto’s thyroiditis is characterized by the production of immune cells and autoantibodies by the body’s immune system that can damage thyroid cells and compromise their ability to make thyroid hormone. Hypothyroidism occurs if the amount of thyroid hormone which can be produced is not enough for the body’s needs. The thyroid gland may also enlarge, forming a goiter.
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.
Signs & Symptoms
Hashimoto’s thyroiditis may not cause symptoms for many years and may 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 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, and this pressure on surrounding structures may cause additional symptoms, including difficulty swallowing.
Although many of the symptoms 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 with 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 progresses in many patients, causing a slow worsening of symptoms. Therefore, patients 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.
A physician experienced in the diagnosis and treatment of thyroid disease can detect a goiter due to Hashimoto’s thyroiditis by performing a physical examination and can recognize hypothyroidism by identifying characteristic symptoms, finding typical physical signs and performing appropriate laboratory tests.
Antithyroid Antibodies-Testing for increased antithyroid antibodies provides the most specific laboratory evidence of Hashimoto’s thyroiditis, but the antibodies are not present in all cases.
TSH (Thyroid-Stimulating Hormone or Thyrotropin) Test – Increased TSH level in the blood is the most accurate indicator of hypothyroidism. TSH is produced by another gland, the pituitary, which is located behind the nose at the base of the brain. The level of TSH rises dramatically when the thyroid gland even slightly underproduces thyroid hormone. So, in patients with normal pituitary function, a normal level of TSH reliably excludes hypothyroidism.
Free thyroxine estimate – the active portion of all of the thyroxine circulating in the blood. A low level of free thyroxine is consistent with thyroid hormone deficiency. However, free thyroxine values in the “normal range” may actually represent thyroid hormone deficiency in a particular patient, since a high level of TSH stimulation may keep the free thyroxine levels “within normal limits” for many years.
Fine-needle aspiration of the thyroid – usually not necessary for most patients with Hashimoto’s thyroiditis, but a good way to diagnose difficult cases and a necessary procedure if a thyroid nodule is also present.
For patients with thyroid enlargement (goiter) or hypothyroidism, thyroid hormone therapy is clearly needed, since proper dosage corrects any symptoms due to thyroid hormone deficiency and may decrease the goiter’s size. Treatment generally consists of taking a single daily tablet of levothyroxine. Older patients who may have underlying heart disease are usually started on a low dose and gradually increased, while younger, healthy patients can be started on full replacement doses at once.
While you may improve in many ways within a week, the full impact of thyroid medicine may take quite some time. For example, skin changes may take up to 3-6 months to resolve. Because of the generally permanent and often progressive nature of Hashimoto’s thyroiditis, it is usually necessary to treat it throughout one’s lifetime and to realize that dosage of medicine required may have to be adjusted from time to time.
Optimal adjustment of thyroid hormone dosage, guided by laboratory tests rather than symptoms alone, is critical, since the body is very sensitive to even small changes in thyroid hormone levels. Levothyroxine tablets come in 12 different strengths, and it is essential to take them in a consistent manner every day. If the dose is not adequate, the thyroid gland may continue to enlarge and symptoms of hypothyroidism will persist. This may be associated with increased serum cholesterol levels, possibly increasing the risk for atherosclerosis and heart disease. If the dose is too strong, it can cause symptoms of hyperthyroidism, creating excessive strain on the heart and an increased risk of developing osteoporosis.
– American Association of Clinical Endocrinologists