Hashimoto's syndrome

Hashimoto's syndrome is an autoimmune disorder thought to result from a combination of genetic and environmental factors. Some of these factors have been identified, but many remain unknown. People with Hashimoto’s syndrome have antibodies to various thyroid antigens. The antibodies mistakenly "attack" the thyroid, resulting in damage to the gland.

Several genes appear to be possible risk factors for Hashimoto syndrome, such as the gene family called the human leukocyte antigen (HLA) complex, which helps the immune system distinguish the body's own proteins from proteins made by viruses and bacteria or other agents. It is also more common in people who have other family members with the disease. However, the genetic factors have only a small effect on a person's overall risk of developing this syndrome. Non-genetic factors that may trigger the syndrome in people at risk may include changes in sex hormones (particularly in women), viral infections, high cholesterol, vitamin D deficiency, certain medications, exposure to ionizing radiation, and excess consumption of iodine (a substance involved in thyroid hormone production).

Hashimoto’s syndrome is much more frequent in women than men, especially between the ages of 40 and 60 years old.

Hashimoto’s syndrome is associated with other autoimmune diseases, including connective tissue diseases, joint diseases (such as autoimmune types of arthritis), pernicious anemia, adrenal insufficiency, celiac disease, and type 1 diabetes mellitus. Also, people with autoimmune diseases seem to have a higher risk of developing Hashimoto's syndrome.

The way Hashimoto's syndrome may be passed down in a family (inheritance pattern) is unclear, because many genetic and environmental factors appear to be involved. However, the syndrome can cluster in families, and having a close relative with Hashimoto's syndrome or another autoimmune disorder likely increases a person's risk of developing the syndrome.

Hashimoto's syndrome that is untreated or poorly treated can cause problems for both a pregnant woman and a developing fetus. It is recommended that affected women plan their pregnancies and make sure that thyroid function is well-controlled before becoming pregnant. Women with Hashimoto's syndrome should consult with their health care providers prior to pregnancy.

Potential complications of an underactive thyroid in a pregnant mother may include preeclampsia, anemia, miscarriage, placental abruption, and/or postpartum bleeding.

A developing fetus' brain and nervous system need thyroid hormone to develop normally. During the first trimester, the fetus depends on the mother’s supply of thyroid hormone. Effects of a mother's underactive thyroid on a fetus may include preterm birth, low birth weight, birth defects, thyroid problems, and/or stillbirth.

During pregnancy, the body needs higher amounts of some nutrients to support the health of both the mother and fetus. In addition to making sure thyroid hormone levels are within the normal range, it is recommended that pregnant women maintain a balanced diet and take prenatal vitamins. Affected women should also speak with their health care provider about their intake of iodine, which is necessary for thyroid health.

The thyroid uses iodine to make thyroid hormone, so iodine is particularly important for a pregnant woman. The fetus only gets iodine from the mother's diet, so women need more iodine during pregnancy. However, people with an autoimmune thyroid disease may be sensitive to harmful side effects from iodine. Taking iodine drops or eating foods containing large amounts of iodine (such as seaweed, dulse, or kelp) may worsen hypothyroidism. Changes in diet and the use of dietary supplements (especially during pregnancy) should always be discussed with a health care provider to make sure any changes or additions to the diet are safe for both the mother and developing fetus.

We are not aware of recommended alternative treatments for pregnant women with Hashimoto's syndrome. While there is some literature that discusses complementary and alternative therapies for thyroiditis in general, we are not aware of therapies specific to pregnant women. Alternative therapies may help when used along with medications prescribed by your doctor, but it is strongly recommended that affected people first discuss with their doctor any alternative therapies they are considering (especially before or during pregnancy). Some therapies and supplements can interfere with conventional medications or affect other processes in the body.

Women with Hashimoto's syndrome may need to see their obstetrician or perinatologist, and an endocrinologist. The goal of treatment is to normalize maternal levels of thyroid hormones. Thyroid hormone replacement using synthetic thyroxine (such as levothyroxine) is both safe and necessary for the health of the mother and developing fetus. Women with Hashimoto's syndrome who are planning to become pregnant should speak with their health care provider prior to pregnancy to make sure their hypothyroidism is corrected. Women who are being treated usually need a higher dose to maintain normal thyroid function during the pregnancy, and there are specific ranges of ideal hormone levels for each trimester of pregnancy. Therefore, it is recommended that thyroid function be checked often during pregnancy so adjustments to the dosage can be made.

Again, women with thyroid conditions should consult with their health care providers before and during the pregnancy for an individualized treatment plan.

The National Endocrine and Metabolic Diseases Information Service, a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), provides information on this topic. Click on the link to view the information on this topic.