Overtreatment for hypothyroidism causes levels of thyroid-stimulating hormone (TSH) to drop too low, which can lead to hyperthyroidism.

Hypothyroidism is an underactive thyroid. This means the thyroid gland, in the front of the neck, does not make enough thyroid hormones for the body to function correctly.

Thyroid hormones help regulate metabolism and affect multiple organs and systems in the body. Low levels of thyroid hormones can slow down many bodily functions.

Treating hypothyroidism is essential to help prevent serious health issues. However, overtreating hypothyroidism can also cause serious health problems, so it is important to restore levels to a typical range.

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TSH triggers the thyroid gland to release thyroid hormones. High levels of TSH can be a sign of hypothyroidism.

Treatment for hypothyroidism involves reducing TSH to regular levels using medication, commonly the hormone drug levothyroxine (Synthroid). This can help relieve symptoms of hypothyroidism.

Overtreating hypothyroidism means thyroid medication causes TSH levels to drop too low. This can cause symptoms of hyperthyroidism, which means there are excess levels of thyroid hormones in the body.

A 2022 study defined overtreatment as TSH levels lower than 0.5 milli-international units per liter (mIU/L). Normal levels with thyroid medication were TSH levels between 0.5 and 5.5 mIU/L.

Doctors monitor thyroid levels during treatment, but maintaining thyroid hormone levels can be difficult. Even with frequent monitoring and dosage adjustments, overtreatment or undertreatment may still occur.

Levothyroxine dosing varies for each individual and may need to change to reflect various factors throughout a person’s life, such as:

  • body weight
  • age
  • other medical conditions
  • other medications
  • hormonal changes, such as pregnancy

A 2023 study in Germany looked at the prevalence of overtreatment with levothyroxine. Out of 662 people taking levothyroxine, 18% had overtreatment, and 4% had undertreatment.

The study’s authors also highlight research suggesting that rates of overtreatment range from 14% to 20%.

The authors associated higher doses of levothyroxine with overtreatment. They also suggested that people over 70 years were four times more likely to have overtreatment. The adverse health effects of overtreatment are also more severe in older adults.

Younger people and men were more likely to have undertreatment than women and older adults.

The study suggests overtreatment in older adults may be linked to complex regimens of levothyroxine and varying dosages throughout the week, which may make correct dosing challenging in older adults.

Symptoms of hypothyroidism overtreatment may include:

Overtreatment of hypothyroidism can have severe health risks.

According to the American Thyroid Association (ATA), persistently low levels of TSH can increase the risk of atrial fibrillation. This involves an irregular heartbeat and can increase the risk of stroke.

Overtreatment of hypothyroidism may also increase bone loss and the risk of fractures, particularly in postmenopausal women.

However, the ATA highlights that undertreating hypothyroidism also has risks. Undertreatment means TSH levels remain high, and hypothyroidism symptoms will continue.

Persistently high levels of TSH can increase cholesterol levels, which increases the risk of heart disease.

Both overtreating and undertreating hypothyroidism can increase the risk of heart problems and death from heart disease. Getting the correct treatment and keeping TSH levels within an ideal range is essential to help prevent serious complications.

Doctors will regularly monitor TSH levels throughout a person’s treatment for hypothyroidism. If TSH levels remain too low, a doctor will lower the levothyroxine dosage accordingly.

Once TSH levels reach an expected range, a doctor may recheck levels in 3 to 6 months. After this, a doctor may check levels each year.

If difficulty sticking to a treatment regimen contributes to overtreatment, a doctor may change how people take the medication. This may include a healthcare professional overseeing weekly oral treatment or levothyroxine injections.

A doctor may also address any other issues that could be affecting treatment adherence, such as mental health issues.

If people notice any symptoms of overtreatment for hypothyroidism, they should seek medical advice. It is important not to adjust any medication themselves before talking with a doctor.

A doctor can take tests to check thyroid hormone levels and adjust the dosage of medications if necessary. They may also check for other factors that could be affecting thyroid levels, such as other health conditions, medications, or supplements.

Doctors prescribe thyroid medication, such as levothyroxine, to treat hypothyroidism. Overtreatment for hypothyroidism can occur if people have an excess of thyroid medication.

People will typically have long-term treatment for hypothyroidism. This can mean changes in weight, hormone levels, and health can all occur, which can affect levels of thyroid hormones and thyroid medication in the body.

Keeping thyroid levels within a certain range helps prevent serious health risks. Overtreatment and undertreatment of hypothyroidism can cause serious health risks, including heart disease.

If people notice any symptoms of hypothyroidism overtreatment, they should contact a doctor.