Thyroid Risk Factors

Thyroid Risk Factors

by Rashmi Gulati, MD
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When considering our risk for developing diseases of any kind, it's always helpful to remind ourselves that each of us is a unique individual, not simply a number among millions. Through epidemiology, the study of factors that affect the health of different populations, we do see certain factors that place some populations at higher risk than others for developing thyroid problems. Through study of people with thyroid disorders, we also know that having a thyroid problem is associated with particular related health risks.

Fortunately, given timely and accurate diagnosis, most thyroid conditions respond readily to treatment, and can be well-managed with appropriate care in follow-up.

Some of the associations seen by epidemiologists, health care providers, and research scientists between these various thyroid conditions and factors are discussed here.

Associated Health Risks of Thyroid Disease

Hyperthyroidism

Risk Factors for Thyroid Disease

Some factors that place an individual at higher risk of thyroid disease include the following:

  • Age and Gender. Hypothyroidism occurs more commonly in older populations, and women are more prone than men to develop a thyroid condition.
  • Family History. Thyroid disorders have a number of familial associations. Researchers are working to elucidate genetics of thyroid conditions and ways to minimize risks.
  • Prior Personal History. Risk of developing hypothyroidism in the future is increased by having an existing thyroid disease, goiter or nodules, or having undergone surgery or radiation therapy to treat thyroid problems.
  • Medical Conditions. Autoimmune disorders such as diabetes, pernicious anemia, vitiligo, and premature graying of the hair are among the conditions seen more commonly in association with hypothyroidism.
  • Iodine Status. While thought to be rare in the United States, epidemiological studies suggest iodine deficiency is currently on the upswing, particularly in women of childbearing age. Having your iodine status checked as a potential risk for thyroid dysfunction is well worthwhile, however, for numerous reasons. First, many topsoils are being increasingly depleted of their mineral stores, many people eat very little seafood, many people use very little (iodized) table salt, and the iodine content of even "iodized salt" can quickly dissipate. What's more, many scientists believe iodine is being displaced in the body by environmental exposure to molecules in the same chemical family, known as halides. These include fluoride, chloride, and bromide, in the form of fluoridated water, perchlorates from jet fuel pollution, and bromates, which are added to most commercial flours and used liberally as soil fumigants.
  • Selenium Status. The mineral selenium is required for the deiodination process that turns T4 into the active T3 form. Having your selenium status evaluated is a simple commonsense measure to ensure your levels are adequate and minimize any effect a deficiency could have on thyroid hormone balance.
  • Medications. Use of certain medications, including lithium, amiodarone, and interferon can alter thyroid function.

Patients with untreated hyperthyroidism may be placed at increased risk for a number of associated complications. As increased levels of circulating thyroid hormones shift the body's metabolism into overdrive, weight loss can occur to an extent that poses problems over the long-term. Osteoporosis can potentially develop if thyroid hormonal imbalance interferes with the normal transport and storage of calcium and other minerals in the bones. Cardiovascular health is at risk due to sustained irregularities in heartbeat. Should atrial fibrillation develop, the patient may experience chest pains, blood clots, even heart failure. Chronic fatigue, tremors, muscle weakness, or severe muscle spasms can also develop.

Hyperthyroidism can also lead to various problems with the eyes, including redness, swelling, blurring, and double vision. Protrusion of the eyes is characteristic of Graves' disease, but other thyroid disorders leading to an overabundance of hormones can also give the eyes a widened, somewhat surprised appearance.

Untreated hyperthyroidism can also place a patient at risk for thyrotoxic crisis, a complication triggered by extreme stress or illness. During these episodes, the heart rate increases dramatically and the heartbeat may become irregular. Severe nausea, vomiting, and diarrhea can also occur, putting the patient at risk for dehydration, coma, and death.

Hypothyroidism

Untreated hypothyroidism may lead to an enlarging goiter due to high levels of thyroid-stimulating hormone. This constant stimulation of the thyroid gland by TSH causes proliferation of thyroid follicles as the body attempts to compensate. As the thyroid continues to increase in size, it may significantly crowd other structures in the neck, causing difficulties with breathing and swallowing.

Insufficient thyroid hormone levels can indirectly cause an increase in serum triglycerides and LDL cholesterol (the "bad" cholesterol), contributing to an increased risk of cardiovascular conditions such as atherosclerosis, heart attack, and stroke.

Hypothyroidism can also impact mood, leading to irritability, depression, and general mood instability. Cognitive problems, such as memory loss, diminished attention span, and brain fog can also be experienced. Chronic pain, chronic fatigue, and an increased need for sleep may also be more likely in patients with low thyroid function.

Untreated hypothyroidism can induce myxedema, a condition associated with tissue swelling, accumulation of fluid around the heart and lungs, a slowing of muscle reflexes, and decreased ability to think clearly. More rarely, in the case of long-term untreated hypothyroidism, an individual may suffer episodes of profound sleepiness, and lapse into an unconsciousness state called myxedema coma. These episodes may be triggered by stress, illness, or the use of painkiller medications.

Thyroid Disorders and Risk Factors for Women

Various abnormal thyroid states are diagnosed five to seven times more frequently in women than in men. The thyroid undergoes significant change across a woman's life span, with cyclic modifications during menstrual cycles, increases in size during pregnancy, and functional changes through the menopausal transition and into advanced age. The incidence increases with age, with an estimated 1 in 5 women over the age of 60 having subclinical hypothyroidism.

Thyroid disorders can increase a woman's risk of menstrual irregularities and female infertility. Should a woman with thyroid imbalance become pregnant, it is crucial that the imbalance be corrected, to ensure normal fetal development as well as to protect her long-term health.

Untreated hyperthyroidism or hypothyroidism during pregnancy is associated with increased incidence of miscarriage, stillbirth, and birth defects. It is generally safe to take thyroid hormone supplements during pregnancy, and dosages may require adjustment as the pregnancy progresses and interaction between the mother's metabolic pathways and the fetus's change. Women with hyperthyroidism ideally will have their condition well-managed before becoming pregnant, as certain treatments for hyperthyroidism may be contra-indicated for a developing fetus.

Thyroid Nodules and Thyroid Cancer Risks

Nodules discovered in the thyroid should always be thoroughly evaluated to determine their nature and possible etiology. Enlarging nodules can impinge on surrounding tissues and may impair swallowing and breathing. The development of nodules can also be a sign of thyroid cancer.

Papillary and follicular thyroid cancers, which together comprise almost 90% of thyroid cancer cases, tend to have good recovery rates, though diligent monitoring of the thyroid for recurrence should continue. Medullary and anaplastic thyroid cancers tend to be more invasive, and more likely to spread to other organs, making them far more difficult to treat.

The prognosis for patients with forms of thyroid cancer other than anaplastic is generally good, but generally poor for those with anaplastic thyroid cancer. New treatment protocols are being developed that combine the latest advances in surgery, chemotherapeutic drugs, radiation therapy, and adjunctive modalities to help prolong life for these patients.

Risk Factors for Thyroid Disease and Associated Health Risks—
Citations and Further Reading


Date of Publication: 09/05/2005
Article Last Updated: 01/23/2014

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