Thyroid Disorders

There are two main types of thyroid dysfunction:

  • Hypothyroidism (underactive thyroid)
  • Hyperthyroidism (overactive thyroid)

Hypothyroidism is the underproduction of thyroid hormones resulting from:

  • An autoimmune disorder (Hashimoto’s disease). This causes the body to produce antibodies that identify thyroid tissue as foreign and destroy it
  • Iodine deficiency
  • Surgical removal of the thyroid (due to cancer, for instance)
  • Certain medications

Symptoms vary. They depend on age, severity and duration of the hormone deficiency.

Symptoms include:

  • Fatigue
  • Sluggishness
  • Weight gain
  • Memory problems
  • Hair loss
  • Depression
  • Difficulty sleeping and swallowing
  • Constipation
  • Muscle pain
  • Mood swings
  • Dry skin
  • Menstrual irregularity
  • Intolerance to cold
  • Hoarseness
  • Muscle weakness or cramps

Untreated hypothyroidism can cause:

  • Enlargement of the thyroid (goiter)
  • High cholesterol levels
  • Infertility in women of reproductive age

In older people:

  • The disorder may cause confusion and thus may be misdiagnosed as dementia.

In pregnant women, an underactive thyroid increases the risk of:

  • Premature labor
  • Fetal damage
  • Low-birth-weight babies
  • Miscarriage

Hypothyroidism is almost always treated with levothyroxine.

It’s estimated that 5%-10% of American adults have at least some degree of thyroid dysfunction.

  • Hypothyroidism is much more common than hyperthyroidism.
  • The risk increases at older ages.
  • Women are five to eight times more likely to have hypothyroidism than men.
  • Having an autoimmune disease, such as type 1 diabetes or rheumatoid arthritis, increases the risk.
  • Family history of thyroid or autoimmune disease increases risk.

Hypothyroidism is caused by:

  • Iodine deficiency
    • This is no longer a significant problem in the U.S. and Canada.
    • That’s because iodine is now widely dispersed in the food supply, primarily via iodized salt.
  • Smoking (which may adversely affect the thyroid)

Thyroid dysfunction is not caused by factors you can modify. That means it isn’t caused by things like diet or lack of exercise.

Detecting hypothyroidism

Your doctor can check for thyroid problems by checking your symptoms (if any) and doing a physical exam. Yet, it may be hard to spot on an exam. Symptoms can be mild or nonexistent.

In addition, many of the symptoms, like fatigue, are vague. It can also be caused by a variety of other common ailments. This is especially likely to happen in older people. All of these factors can lead to misdiagnosis.

The most common blood test to screen for thyroid dysfunction measures thyroid stimulating hormone (TSH).

  • TSH is produced by the pituitary gland. It stimulates the release of hormones by the thyroid.
  • When the thyroid does not secrete enough hormones, the pituitary normally prods it to produce more by increasing TSH.
  • This is why a high TSH level usually indicates hypothyroidism. A low TSH level, hyperthyroidism.

Normal TSH levels can vary markedly from person to person as well as from season to season, day to day, even hour to hour.

  • Factors such as age, sex, and overall health play large roles.
  • Some medications, such as corticosteroids and dopamine, can alter thyroid function and thus TSH values.

For all these reasons, if TSH results are only mildly to moderately abnormal, the test should be repeated over several months to confirm the finding. In about one-third of people, elevated TSH levels return to normal within a few years without treatment.

Who should be tested, and when to treat

Routine screening for thyroid problems remains controversial. It’s clear that testing should be done if people have symptoms or signs that may indicate thyroid problems. Many doctors commonly include TSH as part of routine blood work.

Some medical groups recommend routine screening, at least for certain groups. For instance:

  • The American Thyroid Association advises screening everyone over age 35 every five years.
  • The American Association of Clinical Endocrinologists advises screening older people, especially women.

The U.S. Preventive Services Task Force (USPSTF) has concluded that there isn’t enough evidence to assess the balance of benefits and harms of routinely screening people without symptoms. Since it couldn’t determine if such screening is beneficial overall, it did not recommend for or against it.

What are the risks?

Overt hypothyroidism poses known health risks, notably to the cardiovascular system. Yet, research has been mixed about the adverse effects of mild hypothyroidism. Many studies have linked it to atherosclerosis and increased risk of coronary artery disease, heart failure, and cardiac dysfunction. But others have not.

Bottom line

You should be screened if you have:

  • Symptoms or signs that suggest thyroid dysfunction
  • A family history of a thyroid problem
  • A personal or family history of autoimmune disease (such as type 1 diabetes)

Other signs for screening include:

  • Having had radiation to the neck
  • Having used lithium or certain other medications

If you’re a woman over 60 or are pregnant, or trying to get pregnant, talk to your doctor about thyroid screening.

If you have hypothyroidism and have been put on levothyroxine:

  • You must be monitored to make sure your dosage is correct
  • Many people are accidentally given doses that are too high
  • High doses can lead to hyperthyroidism, which has its own risks

If you only have hypothyroidism, but no symptoms, be cautious about starting medications. And if you have been taking levothyroxine, discuss if it is really necessary. Many people take the drug for years without proper reevaluation.

Subclinical hypothyroidism

More than 15% of older Americans take thyroid hormone. And its use has risen. The increase has mostly been in people with subclinical hypothyroidism. This is defined as an elevated blood level of thyroid stimulating hormone (TSH) but a normal level of the thyroid hormone thyroxine (T4).

People who experience fatigue, weight gain, hair loss, depression, and “brain fog” may attribute these and other symptoms to subclinical hypothyroidism. Keep in mind that such symptoms could be due to a range of other conditions. Studies suggest that many people with subclinical hypothyroidism may be taking thyroid hormone unnecessarily. This is particularly true in older adults.

One study1 issued a “strong recommendation” against routinely prescribing thyroid hormone for people with subclinical hypothyroidism. This was because the hormone didn’t show any benefits for quality of life or thyroid-related symptoms (depression, fatigue, body mass index).

The recommendation doesn’t apply to these groups:

  • People with a “very high” TSH (which the panel defined as above 20) but a normal T4 level
  • People with severe symptoms
  • People who are younger than 30
  • Pregnant women

Another review2 added that there is no evidence that levothyroxine therapy for subclinical hypothyroidism is beneficial in people 65 and older. The review concluded that most people with subclinical hypothyroidism should be monitored by their doctors. This is instead of being treated with levothyroxine.

If you are taking levothyroxine, you should have your thyroid hormone levels tested regularly to make sure the dosage isn’t too high. This in effect can cause hyperthyroidism. And don’t stop taking the medication without medical advice.

The flip side of hyperthyroidism

When the thyroid gland overproduces hormones, it’s called hyperthyroidism. In the U.S., this disorder is most commonly caused by Graves’ disease.

  • An overactive thyroid revs up your metabolism. This causes symptoms such as:
    • Nervousness
    • Rapid or irregular heart rate
    • Weight loss
    • Irritability
    • Anxiety
    • Insomnia
    • Muscle weakness
    • Tremors
    • Sleep and vision problems
    • Goiter
    • Palpitations
    • Menstrual irregularity
    • Heat intolerance
    • Impaired fertility
  • Bulging eyes (exophthalmos) is a sign of Graves’ disease.

In response to the overproduction of thyroid hormones:

  • The pituitary gland normally lowers TSH levels, signaling the thyroid to put on the brakes.
  • Thus, a low blood level of TSH often means you have hyperthyroidism.

Untreated hyperthyroidism can cause reduced bone mineral density and a host of heart disorders, including:

  • Abnormal heart rhythms (atrial fibrillation)
  • Hypertension
  • Angina
  • Heart failure

Some recent research has linked even modestly high levels of thyroid hormones to heart disease.

Hyperthyroidism can be treated with drugs that block hormone production. But more commonly, the thyroid gland is inactivated with radioactive iodine. After that, oral thyroid hormones must be taken.

Cholesterol/thyroid connection

Lack of thyroid hormones decreases the liver’s ability to clear cholesterol from the blood. That is why people with hypothyroidism tend to have:

  • High low-density lipoprotein (LDL “bad”) cholesterol
  • High triglycerides

This may be one reason why hypothyroidism is linked with increased risk of atherosclerosis and heart attacks.

If you have high LDL cholesterol:

  • Your doctor should check to see if you have hypothyroidism, especially if you are a woman over 60

If so, it makes sense to treat the thyroid condition first. In some cases, treating it may reduce cholesterol. However, studies on the effect of treatment of mild hypothyroidism on cardiovascular outcomes have had mixed results.

Medication adherence

The World Health Organization defines medication adherence as “the degree to which the person’s behavior corresponds with the agreed recommendations from a health care provider.” Poor adherence to prescribed regimens can result in serious health impacts including hospitalization and death.

About half of all medications for chronic diseases are not taken correctly. People change or skip doses, stop too soon, don’t take them at all, or never fill their prescriptions.

What to do when you get a new medication:

  • Take notes on what your doctor tells you about the medication.
  • Double check with the pharmacist on how to take the medication.
  • Ask questions to make sure you fully understand the medication. Be clear about when and how to take it.
  • Creating a chart for your daily medication regimen can help you stay on track. So might a pill box with multiple sections. This is helpful if you take more than one medication. This is also helpful if you take medications more than once a day. 
  • If you’re being treated for a chronic condition, check regularly with your doctor about whether you are taking the medication(s) correctly.
  • If you are concerned about or are experiencing side effects, talk to your doctor.
  • Do not take yourself off of medications without the knowledge and guidance of your doctor.
  • If you’re having trouble sticking to your medication, for any reason, talk with your doctor. They may be able to suggest other treatments or refer you to services that can help.