Hypothyroidism Diagnosis

  • Diagnosis

    Hypothyroidism is a condition in which the level of the thyroid hormones in the body is abnormally low. The thyroid gland is the butterfly-shaped organ located at the base of the throat. It secretes two important hormones—T3 and T4—that the body needs to function well. These hormones regulate how quickly the body converts the nutrients from oxygen and food into energy. Heart rate, weight, body temperature, alertness, and mood are among the many things affected by thyroid hormones. When then thyroid gland becomes underactive, thyroid hormone levels dip.

    Two other glands—the hypothalamus and the pituitary gland—work together with the thyroid to regulate thyroid hormone levels. There are many things that can interfere with the functioning of all these organs, and, consequently, thyroid hormone levels. For example, the pituitary gland, located in the brain, is one of the “master glands,” and controls other glands in the body. It makes a hormone called thyroid-stimulating hormone (TSH), which is involved in hypothyroidism. TSH instructs the thyroid gland to produce T3 and T4 when levels of those hormones are low. Likewise, if levels of T3 and T4 in the blood are too high, the pituitary gland “turns off” the thyroid gland.

    The hypothalamus gland, another “master gland” of the brain, is similarly involved in thyroid hormone levels, providing a feedback loop to keep levels in check. If either of these glands is not functioning properly, then hypothyroidism results.

    Hashimoto’s thyroiditis is the most common cause of hypothyroidism. Hashimoto’s thyroiditis occurs when a person’s own immune system attacks the thyroid gland, causing the gland to become inflamed initially, and then become underactive. Immune diseases can run in families, and are more common in women. Hashimoto’s thyroiditis is no exception, as it is particularly common in women—especially as they age. The disease is also linked to other autoimmune diseases, such as diabetes and rheumatoid arthritis.

    Hypothyroidism can develop when treatments to correct an overactive thyroid cause the gland to shut down.

    • Undergoing surgery or receiving radioactive iodine treatment, which might be done to keep the thyroid from churning out too much thyroid hormone, can disable the gland.
    • Radiation therapy for certain types of cancer also commonly disables the thyroid gland, causing hypothyroidism.
    • Medications such as lithium (Eskalith, Lithane, Lithobid, Cibalith-S) and amiodarone (Cordarone), as well as surgery for throat cancer or Hodgkin’s disease, can produce hypothyroidism.

    Rarely, hypothyroidism stems from a problem with the pituitary gland. Pituitary tumors and other pituitary disorders can affect the hormonal chain of command that governs thyroid function, and result in underproduction of thyroid hormone.

    Not getting enough dietary iodine is another cause of hypothyroidism, but is not commonly seen in the U.S. Iodine is a trace element that is needed to make thyroid hormone. In this country, iodine-deficiency hypothyroidism is rare, thanks to the introduction of iodized salt in the 1920s.

    The symptoms of an underactive thyroid gland are fairly general and common. They stem from a metabolic slow-down, and include such things as weight gain, constipation, fatigue, and depression. Table 01 If you have suffered from constipation on and off for much of your life, chances are it is not because of your thyroid. However, if your symptoms start suddenly and last for more than a few weeks, consult your doctor. Likewise, gaining and losing a few pounds every once in a while is normal, but if you have been putting on weight for some time without having changed your diet or activity level, you might want to get your thyroid checked.

    Table 1.  Symptoms of Hypothyroidism

    Fatigue
    Weight gain
    Constipation
    Hair loss
    Sensitivity to cold temperatures
    Depression
    Mental slowness, memory problems
    Reduced sex drive
    Heavy menstruation
    Muscle cramps
    Dry skin
    Numbness and tingling in hands and feet

    Hypothyroidism occurs most often in women over the age of 50. Ten times as many women as men have an underactive thyroid. Older women are especially vulnerable. An estimated 8% to 10% of women over the age of 50 have underactive thyroid glands.

    Women who have recently given birth are at risk for thyroid problems. Thyroid dysfunction complicates 5% to 9% of pregnancies, typically resulting in two to eight months of overactivity (hyperthyroidism) followed by two to eight months of underactivity (hypothyroidism). This is called post-partum thyroiditis—it usually goes away on its own, but a quarter of women who have it develop a permanently underactive gland.

    A family history of thyroid problems increases the likelihood of hypothyroidism.

    People who have diabetes, anemia caused by failure to absorb vitamin B12 (pernicious anemia), or insufficiency of the adrenal glands are more prone to the problem.

    Having received prior radiation or x-ray treatments to the neck increases a person's risk for hypothyroidism. Many people who have hyperthyroidism get treated with thyroid irradiation. This makes them hypothyroid, and then they take medicine to normalize the thyroid level in their body.

    Hypothyroidism can be confirmed with simple blood tests to measure hormone levels. The conventional way to tell if your thyroid is sluggish is to measure the amount of T4 and TSH circulating in your blood. If your thyroid is clearly underproductive, your test will reveal a low level of T4 and a high level of TSH. If you are in the early stages of hypothyroidism, however, your test may show an elevated TSH level only. If Hashimoto’s thyroiditis is the cause of your thyroid dysfunction, your blood may contain antibodies directed toward the thyroid. If your hypothyroidism is caused by your pituitary gland, your blood tests will show a low level of T4 and a normal or low level of TSH.

    Once you are diagnosed with hypothyroidism, you will need regular testing to monitor your hormone levels, which may decline over time.

    Starting at age 35, you should get your thyroid checked every five years. Because thyroid problems are not always obvious, the American Thyroid Association (ATA) recommends routine screening for all adults. If you have a family history of thyroid problems or you have diabetes, pernicious anemia, or adrenal insufficiency, the ATA suggests getting screened even more frequently. There is no way to prevent hypothyroidism, but frequent screening can alert your doctor to the condition.

  • Prevention and Screening

    Starting at age 35, you should get your thyroid checked every five years. Because thyroid problems are not always obvious, the American Thyroid Association (ATA) recommends routine screening for all adults. If you have a family history of thyroid problems or you have diabetes, pernicious anemia, or adrenal insufficiency, the ATA suggests getting screened even more frequently. There is no way to prevent hypothyroidism, but frequent screening can alert your doctor to the condition.

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