Low to high ranges, symptoms, and what they mean

The thyroid-stimulating hormone (TSH) test measures the amount of TSH in the blood. TSH levels convey how well a person’s thyroid is functioning.

Doctors can use TSH test results to diagnose thyroid disorders, such as hypothyroidism and hyperthyroidism.

The pituitary gland produces TSH, which is a hormone that stimulates the thyroid gland.

The thyroid is a butterfly-shaped gland in the throat. It produces hormones that help regulate many bodily functions, such as metabolism, heart rate, and body temperature.

This article describes the TSH test and results. We also discuss what high and low TSH levels indicate and available treatments.

Share on PinterestMNT-infographic_guide infographic by Diego Sabogal 1401179-TSH-levels-original

The normal range depends on a person’s age and whether they are pregnant.

The ranges tend to increase as a person gets older. Research has not shown a consistent difference in TSH levels between males and females.

However, according to the American Thyroid Association, doctors generally consider levels are within a normal range between 0.4–4.0 milliunits per liter (mU/l).

The following table provides estimates of TSH levels that are normal, low (indicating hyperthyroidism), and high (indicating hypothyroidism):

Many labs use these reference values.

However, there is some debate about these ranges. The author of a 2016 review suggests that normal levels are more likely to fall between 0.5–2.5 milli-international units (mIU) per milliliter.

Females are more likely to experience thyroid dysfunction than males. The Office on Women’s Health reports that 1 in 8 females experience thyroid problems at some point. This includes hyperthyroidism and hypothyroidism. The risk of thyroid problems increases during pregnancy and around menopause.

Research does not show a consistent difference in TSH levels between males and females. However, some evidence suggests that TSH levels are generally higher in females. For example, studies in 2020 investigating Chinese and French populations suggest that TSH levels are higher in females, but other factors, such as age, are more likely to affect TSH levels.

In some people, thyroid conditions are linked with sexual dysfunction. This may affect more males than females. According to a 2019 study, 59–63% of males with hypothyroidism also experience sexual dysfunction, compared with 22–46% of females who have hypothyroidism.

Blood TSH levels tend to increase as people get older, with evidence noting that hypothyroidism is the most common thyroid condition in people over 60 and steadily increases with age.

Research involving older adults suggests that roughly 7–14% of people may have TSH levels above the upper limit of reference ranges.

Pregnancy hormones naturally increase the levels of certain thyroid hormones in the blood. This is essential for the development of the fetal brain and nervous system.

At the same time, the levels of TSH in the blood decrease. As a result, doctors use lower reference ranges during pregnancy. The lower TSH range is decreased by around 0.4 mU/l, and the upper limit reduced by approximately 0.5 mU/l.

Levels of TSH in the blood increase gradually during the second and third trimesters, but they remain lower than normal levels in women who are not pregnant.

Doctors carefully monitor TSH levels throughout pregnancy. Having unusually high or low levels can affect the risk of miscarriage and cause pregnancy-related complications, such as:

• preeclampsia
• premature birth
• low birth weight
• congestive heart failure

TSH levels are highest at birth and gradually decrease as a child gets older. As such, TSH levels can vary among children. After the newborn phase, health experts may define mild hypothyroidism in children as TSH levels ranging between 4.5–10 mU/l.

The following table shows TSH levels for children by age, according to an older study using data from 512 healthy children:

High TSH levels indicate hypothyroidism. People develop hypothyroidism when their thyroid produces low levels of hormones.

When someone’s thyroid gland does not produce enough hormones, the pituitary gland produces more TSH to compensate.

Symptoms of hypothyroidism may include:

• fatigue
• weight gain
• swelling of the face and neck
• increased sensitivity to cold temperatures
• dry skin
• thinning hair
• a slow heart rate
• irregular or heavy menstrual periods
• fertility problems
• depression
• constipation

Low TSH levels indicate hyperthyroidism. This is also known as an overactive thyroid.

If a person’s thyroid gland is secreting levels of hormones that are too high, the pituitary gland produces less TSH.

Symptoms of hyperthyroidism can include:

• irregular or rapid heartbeat
• muscle weakness
• nervousness or irritability
• difficulty sleeping
• frequent bowel movements or diarrhea
• weight loss
• mood changes

The TSH test involves a healthcare professional drawing blood from a vein in the inner arm. They then send the blood sample for laboratory testing.

Usually, people do not need to prepare for a TSH test. However, if the doctor is checking the blood for more than one issue, a person may need to fast or prepare in another way. The doctor will provide this information beforehand.

A TSH test is often the best way to monitor thyroid function. However, if a person has abnormally high or low TSH levels, the doctor may need to perform at least one other diagnostic test to identify the underlying cause. These tests look at levels of specific thyroid hormones and antibodies.

In addition to age, sex, and pregnancy, many other factors can also affect TSH levels. Evidence suggests that genetic, environmental, or intrinsic factors can alter TSH levels. Some of these factors may include:

• other conditions occurring at the same time
• medications
• supplements
• ethnicity
• diet and iodine status
• time of day and time of year
• autoantibodies and heterophilic antibodies
• smoking
• pollutants

Doctors can treat hypothyroidism with medications, such as levothyroxine, that replace the missing thyroid hormones.

A person should take this medication once a day or as prescribed. The doctor will monitor how well the treatment is working by running additional blood tests every few months.

According to the Food and Drug Administration (FDA), people should take levothyroxine once a day: in the morning and on an empty stomach, at least half an hour before eating.

The FDA also recommends that a person informs their doctor if they eat soybean flour, walnuts, dietary fiber, or cottonseed meal — these foods can affect how the body processes levothyroxine. Drinking grapefruit juice may also delay the absorption of levothyroxine.

Hyperthyroidism treatments focus on reducing thyroid hormone levels to prevent long-term health complications.

A person may need to take beta-blockers and antithyroid medications.

Another effective treatment is radioiodine therapy. This involves taking a capsule or liquid that contains radioactive iodine-131, which destroys cells that produce thyroid hormones. However, people who take radioiodine therapy may develop hypothyroidism in the future.

Surgical removal of the thyroid gland can treat severe hyperthyroidism. Doctors often reserve this for individuals who cannot take first-line medications and severe cases of hyperthyroidism.

A TSH test measures the amount of the hormone in the blood. Doctors can use the results to diagnose thyroid conditions, such as hypothyroidism and hyperthyroidism.

Normal TSH ranges can vary widely, depending on a person’s age, sex, and weight. Reference TSH ranges remain controversial, but for most people, the normal range falls between 0.4 and 4.0 mU/l.

Having an overactive or underactive thyroid can cause health issues that interfere with a person’s daily life. During pregnancy, unusually high or low TSH levels can lead to complications.

A doctor can provide more information about the TSH test and interpreting the results.

Low to high ranges, symptoms, and what they mean

The thyroid-stimulating hormone (TSH) test measures the amount of TSH in the blood. TSH levels convey how well a person’s thyroid is functioning.

Doctors can use TSH test results to diagnose thyroid disorders, such as hypothyroidism and hyperthyroidism.

The pituitary gland produces TSH, which is a hormone that stimulates the thyroid gland.

The thyroid is a butterfly-shaped gland in the throat. It produces hormones that help regulate many bodily functions, such as metabolism, heart rate, and body temperature.

This article describes the TSH test and results. We also discuss what high and low TSH levels indicate and available treatments.

Share on PinterestMNT-infographic_guide infographic by Diego Sabogal 1401179-TSH-levels-original

The normal range depends on a person’s age and whether they are pregnant.

The ranges tend to increase as a person gets older. Research has not shown a consistent difference in TSH levels between males and females.

However, according to the American Thyroid Association, doctors generally consider levels are within a normal range between 0.4–4.0 milliunits per liter (mU/l).

The following table provides estimates of TSH levels that are normal, low (indicating hyperthyroidism), and high (indicating hypothyroidism):

Hyperthyroidism	Normal	Mild hypothyroidism	Hypothyroidism
0–0. 4	0.4–4	4–10	10

Many labs use these reference values.

However, there is some debate about these ranges. The author of a 2016 review suggests that normal levels are more likely to fall between 0.5–2.5 milli-international units (mIU) per milliliter.

Females are more likely to experience thyroid dysfunction than males. The Office on Women’s Health reports that 1 in 8 females experience thyroid problems at some point. This includes hyperthyroidism and hypothyroidism. The risk of thyroid problems increases during pregnancy and around menopause.

Research does not show a consistent difference in TSH levels between males and females. However, some evidence suggests that TSH levels are generally higher in females. For example, studies in 2020 investigating Chinese and French populations suggest that TSH levels are higher in females, but other factors, such as age, are more likely to affect TSH levels.

In some people, thyroid conditions are linked with sexual dysfunction. This may affect more males than females. According to a 2019 study, 59–63% of males with hypothyroidism also experience sexual dysfunction, compared with 22–46% of females who have hypothyroidism.

Blood TSH levels tend to increase as people get older, with evidence noting that hypothyroidism is the most common thyroid condition in people over 60 and steadily increases with age.

Research involving older adults suggests that roughly 7–14% of people may have TSH levels above the upper limit of reference ranges.

Pregnancy hormones naturally increase the levels of certain thyroid hormones in the blood. This is essential for the development of the fetal brain and nervous system.

At the same time, the levels of TSH in the blood decrease. As a result, doctors use lower reference ranges during pregnancy. The lower TSH range is decreased by around 0.4 mU/l, and the upper limit reduced by approximately 0.5 mU/l.

Levels of TSH in the blood increase gradually during the second and third trimesters, but they remain lower than normal levels in women who are not pregnant.

Doctors carefully monitor TSH levels throughout pregnancy. Having unusually high or low levels can affect the risk of miscarriage and cause pregnancy-related complications, such as:

• preeclampsia
• premature birth
• low birth weight
• congestive heart failure

TSH levels are highest at birth and gradually decrease as a child gets older. As such, TSH levels can vary among children. After the newborn phase, health experts may define mild hypothyroidism in children as TSH levels ranging between 4.5–10 mU/l.

The following table shows TSH levels for children by age, according to an older study using data from 512 healthy children:

Age	Reference ranges (mU/l)
Day of birth	3.84–11.75
1 month	1.18–3.57
1 year	1.17–3.55
5 years	1.15–3.47
12 years	1. 09–3.31
18 years	1.05–3.16

High TSH levels indicate hypothyroidism. People develop hypothyroidism when their thyroid produces low levels of hormones.

When someone’s thyroid gland does not produce enough hormones, the pituitary gland produces more TSH to compensate.

Symptoms of hypothyroidism may include:

• fatigue
• weight gain
• swelling of the face and neck
• increased sensitivity to cold temperatures
• dry skin
• thinning hair
• a slow heart rate
• irregular or heavy menstrual periods
• fertility problems
• depression
• constipation

Low TSH levels indicate hyperthyroidism. This is also known as an overactive thyroid.

If a person’s thyroid gland is secreting levels of hormones that are too high, the pituitary gland produces less TSH.

Symptoms of hyperthyroidism can include:

• irregular or rapid heartbeat
• muscle weakness
• nervousness or irritability
• difficulty sleeping
• frequent bowel movements or diarrhea
• weight loss
• mood changes

The TSH test involves a healthcare professional drawing blood from a vein in the inner arm. They then send the blood sample for laboratory testing.

Usually, people do not need to prepare for a TSH test. However, if the doctor is checking the blood for more than one issue, a person may need to fast or prepare in another way. The doctor will provide this information beforehand.

A TSH test is often the best way to monitor thyroid function. However, if a person has abnormally high or low TSH levels, the doctor may need to perform at least one other diagnostic test to identify the underlying cause. These tests look at levels of specific thyroid hormones and antibodies.

In addition to age, sex, and pregnancy, many other factors can also affect TSH levels. Evidence suggests that genetic, environmental, or intrinsic factors can alter TSH levels. Some of these factors may include:

• other conditions occurring at the same time
• medications
• supplements
• ethnicity
• diet and iodine status
• time of day and time of year
• autoantibodies and heterophilic antibodies
• smoking
• pollutants

Doctors can treat hypothyroidism with medications, such as levothyroxine, that replace the missing thyroid hormones.

A person should take this medication once a day or as prescribed. The doctor will monitor how well the treatment is working by running additional blood tests every few months.

According to the Food and Drug Administration (FDA), people should take levothyroxine once a day: in the morning and on an empty stomach, at least half an hour before eating.

The FDA also recommends that a person informs their doctor if they eat soybean flour, walnuts, dietary fiber, or cottonseed meal — these foods can affect how the body processes levothyroxine. Drinking grapefruit juice may also delay the absorption of levothyroxine.

Hyperthyroidism treatments focus on reducing thyroid hormone levels to prevent long-term health complications.

A person may need to take beta-blockers and antithyroid medications.

Another effective treatment is radioiodine therapy. This involves taking a capsule or liquid that contains radioactive iodine-131, which destroys cells that produce thyroid hormones. However, people who take radioiodine therapy may develop hypothyroidism in the future.

Surgical removal of the thyroid gland can treat severe hyperthyroidism. Doctors often reserve this for individuals who cannot take first-line medications and severe cases of hyperthyroidism.

A TSH test measures the amount of the hormone in the blood. Doctors can use the results to diagnose thyroid conditions, such as hypothyroidism and hyperthyroidism.

Normal TSH ranges can vary widely, depending on a person’s age, sex, and weight. Reference TSH ranges remain controversial, but for most people, the normal range falls between 0.4 and 4.0 mU/l.

Having an overactive or underactive thyroid can cause health issues that interfere with a person’s daily life. During pregnancy, unusually high or low TSH levels can lead to complications.

A doctor can provide more information about the TSH test and interpreting the results.

Thyroid stimulating hormone (TSH)

Thyroid stimulating hormone (TSH) is the main regulator of thyroid function, synthesized by the pituitary gland, a small gland located on the lower surface of the brain. Its main function is to maintain a constant concentration of thyroid hormones – thyroid hormones that regulate the processes of energy production in the body. When their blood levels decrease, the hypothalamus releases a hormone that stimulates the secretion of TSH by the pituitary gland.

Russian synonyms

Thyrostimulating hormone, thyrotropin, TTU.

Synonyms English

Thyroid-stimulating Hormone (THS), Thyrotropin.

Research method

Electrochemiluminescent immunoassay.

Detection range: 0.005 – 1000 µIU/ml.

Units

µIU/mL (microinternational unit per milliliter).

What biomaterial can be used for research?

Venous blood.

How to properly prepare for an examination?

• Children under 1 year of age do not eat for 30-40 minutes before the test.
• Do not eat for 2-3 hours before the study, you can drink clean still water.
• Exclude (in agreement with the doctor) taking thyroid hormones, iodine preparations within 72 hours before the study.
• Exclude (in agreement with the doctor) the use of steroid hormones within 48 hours before the study.
• Avoid physical and emotional overexertion within 24 hours prior to the study.
• Do not smoke for 3 hours prior to the study.

Study Overview

Thyroid stimulating hormone (TSH) is produced by the pituitary gland, a small gland located on the lower surface of the brain behind the sinus cavity. It regulates the production of thyroid hormones (thyroxine and triiodothyronine) according to the “feedback system”, which allows you to maintain a stable concentration of these hormones in the blood. With a decrease in the concentration of thyroid hormones, the secretion of thyroid-stimulating hormone increases and their production by the thyroid gland is stimulated, and vice versa – with an increase in the concentration of thyroxine and triiodothyronine, the secretion of thyroid-stimulating hormone decreases. Thyroid hormones are the main regulators of energy consumption in the body, and maintaining their concentration at the required level is extremely important for the normal functioning of almost all organs and systems.

Pituitary dysfunction can cause an increase or decrease in thyroid-stimulating hormone levels. With an increase in its concentration, thyroid hormones are released into the blood in abnormal amounts, causing hyperthyroidism. With a decrease in the concentration of thyroid-stimulating hormone, the production of thyroid hormones also decreases and symptoms of hypothyroidism develop.

The causes of impaired production of thyroid-stimulating hormone may be diseases of the hypothalamus, which begins to produce increased or decreased amounts of thyreoliberin, a regulator of TSH secretion by the pituitary gland. Diseases of the thyroid gland, accompanied by a violation of the secretion of thyroid hormones, can indirectly (by a feedback mechanism) affect the secretion of thyroid-stimulating hormone, causing a decrease or increase in its concentration in the blood. Thus, the study of TSH is one of the most important tests for hormones.

What is research used for?

• To determine the state of the thyroid gland, an indirect assessment of the production of thyroid hormones.
• To control the therapy of thyroid diseases.
• For the diagnosis of thyroid dysfunction in newborns.
• For diagnosing female infertility and monitoring its treatment.

When is the test scheduled?

1. With an enlarged thyroid gland, as well as with symptoms of hyper- and hypothyroidism.
   • Symptoms of hyperthyroidism:
     • palpitations,
     • increased anxiety,
     • weight loss,
     • insomnia,
     • hand shake,
     • weakness, fatigue,
     • diarrhea,
     • intolerance to bright light,
     • decreased visual acuity,
     • puffiness around the eyes, their dryness, hyperemia, bulging.
   • Symptoms of hypothyroidism:
     • dry skin,
     • constipation,
     • cold intolerance,
     • edema,
     • hair loss,
     • weakness, fatigue,
     • menstrual disorders in women.

• Tests may be ordered at regular intervals to monitor the effectiveness of thyroid therapy. TSH levels are often assessed in newborns at risk for thyroid disease.

What do the results mean?

Reference values ​​

Causes of elevated thyroid-stimulating hormone levels:

• hypothyroidism (primary and secondary),
• pituitary tumor (thyrotropinoma, basophilic adenoma),
• Hashimoto’s thyroiditis,
• syndrome of unregulated secretion of TSH,
• thyrotropin-secreting tumors of the lung,
• adrenal insufficiency,
• preeclampsia,
• lead poisoning,
• mental illness.

Causes of a decrease in the concentration of thyroid-stimulating hormone:

• diffuse toxic goiter,
• TSH-independent thyrotoxicosis,
• thyrotoxic adenoma (Plummer’s disease),
• hyperthyroidism of pregnancy,
• autoimmune thyroiditis with manifestations of thyrotoxicosis,
• mental illness,
• cachexia.

Elevated and decreased levels of thyroid-stimulating hormone indicate thyroid dysfunction, but it is often impossible to determine the exact cause from TSH levels alone. Usually, for this, the level of thyroxine (T4) and triiodothyronine (T3) is additionally determined.

Important Notes

• The following drugs may increase thyroid-stimulating hormone levels: phenytoin, atenolol, clomiphene, motilium, metoprolol, valproic acid, propranolol, amiodarone, calcitonin, prednisolone, morphine, phenothiazine derivatives, benserazide, aminoglutethimide, metoclopramide, furosemide, iodides, lovastatin, methimazole, difenin, rifampicin.
• The level of thyroid-stimulating hormone reflects the situation in the pituitary – thyroid gland over the past 3-6 weeks, so it is advisable to conduct a control determination of the concentration of TSH in the blood 2 months after adjusting the dose of drugs that affect the hormone level.
• The level of thyroid-stimulating hormone can be affected by physical and emotional stress, acute infectious diseases.
• Some studies have shown changes in TSH levels during the day. Therefore, in order to monitor the concentration of TSH, it is recommended to take the test at the same time of day.
• The level of TSH in pregnant women in the third trimester may be elevated.

Also recommended

• Triiodothyronine total (T3 total
• Thyroxine general (T4 general)
• Free thyroxine (T4 free)
• Triiodothyronine free (T3 free)
• Thyroid peroxidase antibodies (anti-TPO)
• Anti-thyroglobulin antibodies (antiTG)

Who orders the examination?

Endocrinologist, internist, pediatrician, gynecologist, neurologist, surgeon.

SANAS Medical Center in Vladivostok

The role of hormones in human life is great. They control the functioning of vital organs. Violation of their balance leads to malfunctions in the body and various diseases that can be asymptomatic at first, and then lead to very serious complications if tests are not taken on time.

These signs indicate that the thyroid gland needs to be checked:

• Enlarged lymph nodes

• Decreased libido or potency in men

• Diseases of the heart

• Depression

• Menstrual irregularity in women

• Hair loss

• Developmental delay (mental and physical in children).

The thyroid gland produces two hormones: thyroxine and triiodothyronine. They are responsible for many vital functions: they regulate the activity of the brain, the nervous and cardiovascular systems, the gastrointestinal tract, affect reproductive function, the functioning of the mammary and sex glands, and much more.

To find out if everything is in order with your thyroid gland, you need to take just one test – TSH (thyroid stimulating hormone). It is he who controls the thyroid gland, therefore he is called regulating. It stimulates the synthesis of other hormones – triiodothyronine (T3) and thyroxine (T4).

The content of TSH in the blood can fluctuate depending on the time of day: at 2-4 am the level of this hormone is very high, while the minimum level occurs around 17-18 pm.

To get an accurate picture, the TSH test should be taken in the morning on an empty stomach. On the eve, you should stop smoking, drinking alcohol, eating a lot of food, and you should also avoid physical and emotional overload.

If the TSH is normal, the gland is working well. If its level is elevated, it means that the thyroid gland has malfunctioned – hypothyroidism or hyperthyroidism.

Hypothyroidism is the most common disease and dysfunction of the thyroid gland. The reason for this is the lack of iodine in the body. The inability of the thyroid to produce enough hormones (T4 and T3) is the most common cause of hypothyroidism, referred to as primary hypothyroidism. Secondary hypothyroidism is much less common.

Table of thyroid hormones.

Chilliness

Some symptoms of hypothyroidism can develop so slowly that the disease can go on for a long time without being diagnosed.

Low TSH can also be caused by diet, stress, inflammation of the pituitary gland.

Signs of an increase in the concentration of “thyroid gland” hormones – hyperthyroidism or thyrotoxicosis:

• Distracted attention, anxiety, insomnia

• High blood pressure and pulse

• Weight loss with good appetite

• Hair loss

• Heart palpitations

• Shortness of breath

Imbalance of TSH and other important hormones can seriously affect a person’s life. It needs to be kept in order. Check your hormone levels at least once a year as a preventive measure, even when there is nothing to worry about. After all, it is better to prevent an ailment in advance than to treat the disease itself.

Medical Center “Sanas” – qualified doctors of the highest category who know their business “from and to”, a reasonable approach to treatment, only the latest European equipment and the convenience of the location of medical centers in different areas.