What are the signs of an increase in TSH level? What are the effects of hypothyroidism on the body? How can it be treated? Find the answers to these questions and more in this detailed article.

Understanding Hypothyroidism: The Thyroid Gland’s Role

Hypothyroidism, or an underactive thyroid, is a condition where the thyroid gland produces too few hormones. The thyroid is a butterfly-shaped gland located in the front of the neck, and its hormones play a vital role in regulating metabolism, energy use, and the function of various organs. Without proper treatment, hypothyroidism can lead to severe complications, such as infertility and heart disease.

12 Common Signs and Symptoms of Hypothyroidism

1. Fatigue

Fatigue is one of the most common symptoms of hypothyroidism. People with the condition often report feeling exhausted, making it difficult to go about their daily activities. This fatigue persists regardless of how much sleep or rest a person gets.

2. Weight Gain and Increased BMI

Thyroid hormones help regulate body weight, food intake, and the metabolism of fat and sugar. Low levels of these hormones can lead to weight gain and an increase in body mass index (BMI), even in mild cases of hypothyroidism. People with the condition may also experience a puffy face and excess weight around the stomach or other areas of the body.

3. Muscle and Joint Issues

Hypothyroidism can affect a person’s muscles and joints, causing aches, pains, stiffness, swelling, tenderness, and weakness. Research also suggests a link between thyroid disorders and rheumatoid arthritis, an autoimmune condition that causes painful joint inflammation.

4. Cognitive and Mood Changes

Thyroid hormones are essential for proper brain function. Untreated hypothyroidism can lead to anxiety, depression, apathy, impaired memory, decreased attentiveness and concentration, and slower thinking and speech. These symptoms can occur because the brain requires thyroid hormones to function correctly.

5. Feeling Cold

Hypothyroidism can slow down metabolism, leading to a drop in core body temperature. As a result, people with low levels of thyroid hormones may feel cold all the time, even in warm environments, and may have cold hands or feet.

6. Digestive Issues

Hypothyroidism can slow down digestion, causing problems with the movement through the gut and the activity of the stomach, small intestine, and colon. This can result in constipation, defined as having fewer than three bowel movements per week, as well as hard stools and a feeling of incomplete bowel emptying.

Other Signs and Symptoms of Hypothyroidism

7. High Cholesterol

Thyroid hormones play a vital role in removing excess cholesterol from the body via the liver. Low hormone levels can lead to increased blood cholesterol levels, with up to 13% of individuals with high cholesterol also having an underactive thyroid. Treating the thyroid problem may help reduce cholesterol levels, even without cholesterol-lowering medication.

8. Cardiovascular Effects

Hypothyroidism can affect the heart, leading to a slower heart rate (bradycardia), changes in blood pressure, variations in heart rhythms, and less elastic arteries. These cardiovascular effects can cause weakness, dizziness, and breathing problems, and without treatment, may result in serious complications such as high or low blood pressure or heart failure.

9. Hair Loss

Thyroid hormones are essential for the growth and health of hair follicles. Hypothyroidism may cause hair loss from the scalp, eyebrows, legs, and other body parts. People with thyroid problems are also more prone to developing alopecia, an autoimmune condition that causes patchy hair loss.

Prevalence and Treatment of Hypothyroidism

Hypothyroidism is a relatively common condition, affecting an estimated 4.6% of the U.S. population. While in the early stages, a person may not notice any symptoms, without treatment, the condition can lead to severe complications. Effective treatment for hypothyroidism, typically with synthetic thyroid hormones, can help manage the symptoms and prevent these complications.

When to Seek Medical Attention

If you experience any of the signs and symptoms of hypothyroidism, it is important to see a healthcare provider. They can perform a blood test to measure your thyroid-stimulating hormone (TSH) levels and diagnose the condition. Early detection and proper treatment are crucial in managing hypothyroidism and its associated health risks.

Conclusion

Hypothyroidism is a complex condition that can have wide-ranging effects on the body, from fatigue and weight gain to cognitive and cardiovascular issues. By understanding the common signs and symptoms of this condition, individuals can seek timely medical attention and receive the necessary treatment to manage their thyroid health and prevent potential complications.

12 signs to look out for

Hypothyroidism, or an underactive thyroid, is when the thyroid gland produces too few hormones. Low levels of thyroid hormones can cause a wide range of signs and symptoms from changes in mental functioning to digestive issues.

The thyroid is a butterfly-shaped gland that sits in front of the neck. Thyroid hormones play a vital role in regulating metabolism and energy use and affect almost all of the body’s organs.

In the early stages, a person may not notice any symptoms. However, without treatment, hypothyroidism can lead to severe complications, such as infertility and heart disease.

In this article, we describe 12 common signs and symptoms of hypothyroidism. We also discuss how common hypothyroidism is and when to see a doctor.

Fatigue is one of the most common symptoms of hypothyroidism.

Many people with the condition report feeling so exhausted that they are unable to go about their day as usual.

The fatigue occurs regardless of how much sleep a person gets or how many daytime naps they take. Treatment for hypothyroidism usually improves people’s energy levels and functioning.

Thyroid hormones help to regulate body weight, food intake, and the metabolism of fat and sugar. People with low levels of thyroid hormones can experience weight gain and an increase in body mass index (BMI).

Even mild cases of hypothyroidism may increase the risk of weight gain and obesity. People with the condition often report having a puffy face as well as excess weight around the stomach or other areas of the body.

Hypothyroidism can affect a person’s muscles and joints in numerous ways, causing:

• aches
• pains
• stiffness
• swelling of the joints
• tenderness
• weakness

Research also suggests a link between thyroid disorders and rheumatoid arthritis, which is an autoimmune condition that causes painful swelling in the lining of the joints. Effective treatment for both conditions will help people manage their symptoms.

It is common for individuals with untreated hypothyroidism to experience:

• anxiety
• depression
• apathy, or general lack of interest or feelings of indifference
• impaired memory function
• less attentiveness and concentration
• low moods
• slower thinking and speech

These symptoms can occur because the brain requires thyroid hormones to function correctly. Research shows that low levels of thyroid hormones can cause changes in brain structure and functioning.

These brain changes can reverse once a person begins treatment.

Share on PinterestA person with hypothyroidism can continually feel cold.

Hypothyroidism can slow down metabolism, which can lead to a drop in core body temperature. As such, some people with low levels of thyroid hormones may feel cold all the time or have a low tolerance of the cold.

This feeling of coldness can persist, even when in a warm room or during the summer months. People with hypothyroidism often report having cold hands or feet, although they may feel that their whole body is cold.

These symptoms are not exclusive to hypothyroidism, however. Circulation problems or anemia can also cause people to feel chilly.

Digestion is another body function that can slow down due to hypothyroidism.

Studies report that an underactive thyroid can cause problems with movement through the gut and the activity of the stomach, small intestine, and colon.

These digestive changes cause some people to experience constipation.

Doctors typically define constipation as having fewer than three bowel movements a week. A person may also have hard stools, difficulty passing stool, or a feeling of being unable to empty the rectum fully.

Thyroid hormones play a vital role in removing excess cholesterol from the body via the liver. Low hormone levels mean that the liver struggles to carry out this function and blood cholesterol levels can increase.

Research suggests that up to 13 percent of individuals with high cholesterol also have an underactive thyroid. As a result, many experts recommend that doctors routinely test people with high cholesterol for hypothyroidism.

Treating the thyroid problem may help reduce cholesterol levels, even in those who do not take cholesterol-lowering drugs.

People with hypothyroidism may also have a slower heart rate, or bradycardia. Low thyroid levels can affect the heart in other ways too. These effects may include:

• changes in blood pressure
• variations in heart rhythm
• less elastic arteries

Bradycardia can cause weakness, dizziness, and breathing problems. Without treatment, this heart condition may result in serious complications, such as high or low blood pressure or heart failure.

Untreated hormone disorders, including thyroid problems, can contribute to hair loss. This is because thyroid hormones are essential for the growth and health of hair follicles. Hypothyroidism may cause hair loss from the:

• scalp
• eyebrows
• legs
• other body parts

People with thyroid problems are also more prone to developing alopecia, which is an autoimmune condition that causes hair to fall out in patches.

An underactive thyroid affects the skin in various ways and can cause symptoms, such as:

• dry, coarse skin
• paleness
• thin, scaly skin

People with hypothyroidism may also develop dry, brittle, and coarse hair or dull, thin nails that break easily.

These symptoms usually clear up once people begin thyroid hormone therapy.

A goiter is an enlargement of the thyroid gland that appears as a swelling at the base of the neck. Other goiter symptoms include:

• a cough
• hoarseness
• problems swallowing and breathing

Many thyroid problems can result in a goiter, including iodine deficiency and Hashimoto’s thyroiditis, which is an autoimmune condition that damages the thyroid gland, stopping it producing enough hormones.

Other causes include underactive thyroid and, less commonly in the United States, iodine deficiency.

People with an underactive thyroid may experience heavy or irregular menstrual periods or spotting between periods.

According to the Society of Menstrual Cycle Research, hypothyroidism causes these problems because it affects other hormones that play a role in menstruation, such as by:

• impairing the detoxification of estrogen
• reducing the amount of sex hormone-binding globulin.

Share on PinterestHypothyroidism is more likely to affect people over 60.

According to the National Institute of Diabetes and Digestive and Kidney Diseases, hypothyroidism affects around 4.6 percent of people aged 12 years or older in the U.S. However, most of these individuals experience only mild symptoms.

Hypothyroidism is more likely to occur in women and people over 60 years of age.

Other risk factors include:

• a personal or family history of thyroid problems
• previous thyroid surgery or radiation treatment to the neck or chest
• having been pregnant recently
• other health conditions, such as Turner syndrome, Sjögren’s syndrome, or certain autoimmune conditions

It is vital for people with unexplained fatigue or other signs or symptoms of hypothyroidism to see a doctor. Without treatment, an underactive thyroid can lead to serious complications, such as infertility, obesity, and heart disease.

A doctor can carry out a simple blood test to check a person’s thyroid hormone levels. Treatment for hypothyroidism involves taking synthetic thyroid hormones. These medications are safe and effective once a person takes the right dose.

Hypothyroidism is a relatively common condition, affecting almost 5 people out of 100 in the U.S. This condition occurs when the thyroid gland does not produce enough hormones.

Because thyroid hormones are essential for the normal functioning of many different parts of the body, low levels can cause a wide variety of symptoms.

Common symptoms include:

• fatigue
• weight gain
• memory and mood changes
• muscle and joint pain.

It is vital that people with these symptoms or other symptoms of hypothyroidism see their doctor for evaluation and treatment. Doctors can prescribe hormone replacement pills to treat individuals with low levels of thyroid hormones effectively.

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Side effects, dosage, uses, and more

1. Levothyroxine oral tablet is available as brand-name drugs. It’s also available in a generic form. Brand names: Levoxyl, Synthroid, and Unithroid.
2. Levothyroxine comes in three forms: an oral tablet, an oral capsule, and an injectable solution.
3. Levothyroxine oral tablet is used to treat hypothyroidism. It’s also used to treat goiter and certain types of thyroid cancer.

Levothyroxine is a prescription drug. It comes as a tablet or capsule you take by mouth. It also comes as an injectable solution that’s only given by a healthcare provider.

Levothyroxine oral tablet is available as the brand-name drugs Levoxyl, Synthroid, and Unithroid. It’s also available as a generic drug. Generic drugs usually cost less than the brand-name version. In some cases, they may not be available in every strength or form as the brand-name drug.

Levothyroxine oral tablet may be used as part of a combination therapy. This means you may need to take it with other medications.

Why it’s used

Levothyroxine oral tablet is used to treat hypothyroidism. This is a condition when your thyroid gland produces too little thyroid hormone.

Levothyroxine also can be used to treat goiter, which is an enlarged thyroid gland. It also treats certain types of thyroid cancer.

How it works

Levothyroxine belongs to a class of drugs called hormones. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

Levothyroxine works by providing the thyroid hormone that your thyroid gland would produce if it were working normally.

Levothyroxine oral tablet can cause side effects.

More common side effects

The more common side effects of levothyroxine can include:

• increased appetite
• weight loss
• heat sensitivity
• excessive sweating
• headache
• hyperactivity
• nervousness
• anxiety
• irritability
• mood swings
• trouble sleeping
• tiredness
• tremors
• muscle weakness
• changes in menstrual periods
• hair loss (usually temporary)
• diarrhea
• vomiting
• stomach cramps

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious side effects

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

• Heart attack. Symptoms can include:
  • chest pain
  • shortness of breath
  • discomfort in your upper body
• Heart failure. Symptoms can include:
  • shortness of breath
  • extreme tiredness
  • swelling in your legs, ankles, or feet
  • unexpected weight gain
• Very fast heart rate
• Irregular heart rhythm

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.

Levothyroxine oral tablet can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.

To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Examples of drugs that can cause interactions with levothyroxine are listed below.

Interactions that increase the risk of side effects

Taking levothyroxine with certain drugs may result in an increase in adverse effects. Examples of these drugs include:

• Antidepressants such as amitriptyline and maprotiline. The side effects of both of these antidepressants and levothyroxine may increase when you take these drugs together. This may put you at risk for irregular heart rhythms (arrhythmias).
• Sympathomimetic drugs such as pseudoephedrine and albuterol. The effects of both the sympathomimetic drugs and levothyroxine may increase when you take these drugs together. This may put you at risk of serious heart problems.
• Blood thinners such as warfarin. Taking these drugs with levothyroxine may increase your risk of bleeding. Your doctor may need to decrease the dosage of your blood thinner if you’re also taking levothyroxine.
• Ketamine. Taking this drug with levothyroxine may increase your risk of high blood pressure and fast heart rate.

Interactions that can make your drugs less effective

When levothyroxine is less effective: When you take levothyroxine with certain drugs, it may not work as well to treat your condition. This is because the amount of levothyroxine in your body may be decreased. Examples of these drugs include:

• The antidepressant sertraline. If you take sertraline with levothyroxine, your doctor might need to increase your levothyroxine dosage to keep it working well for you.
• Rifampin and anti-seizure drugs such as carbamazepine and phenobarbital.
• Calcium carbonate or ferrous sulfate. Take levothyroxine at least 4 hours before or after taking these medications to help make sure that levothyroxine works properly.
• Colesevelam, cholestyramine, colestipol, kayexalate, or sevelamer. Take levothyroxine at least 4 hours before taking these medications to help make sure that levothyroxine works properly.
• Orlistat.
• Simethicone and antacids such as aluminum or magnesium.
• Cancer drugs that belong to the tyrosine-kinase inhibitors class, such as imatinib.

When other drugs are less effective: When certain drugs are used with levothyroxine, they may not work as well. This is because the amount of these drugs in your body may be decreased. Examples of these drugs include:

• Diabetes drugs, such as insulin, metformin, nateglinide, glipizide, and pioglitazone. If you take any of these diabetes drugs with levothyroxine, your doctor may need to increase your dosage of these drugs.
• Digoxin. If you take this drug with levothyroxine, your doctor may need to increase your dosage of digoxin.
• Theophylline. Your doctor may monitor the levels of theophylline in your body if you take it with levothyroxine.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

All possible dosages and drug forms may not be included here. Your dosage, drug form, and how often you take the drug will depend on:

• your age
• the condition being treated
• how severe your condition is
• other medical conditions you have
• how you react to the first dose

Drug forms and strengths

Generic: Levothyroxine

• Form: oral tablet
• Strengths: 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg

Brand: Levoxyl

• Form: oral tablet
• Strengths: 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg

Brand: Synthroid

• Form: oral tablet
• Strengths: 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg

Brand: Unithroid

• Form: oral tablet
• Strengths: 25 mcg, 50 mcg, 75 mcg, 88 mcg, 100 mcg, 112 mcg, 125 mcg, 137 mcg, 150 mcg, 175 mcg, 200 mcg, 300 mcg

Dosage for hypothyroidism

Adult dosage (ages 18–49 years):

• Your dosage will be based on several factors, including your age, weight, thyroid hormone levels, other conditions you have, and other medications you take. The typical dosage is 1.6 mcg/kg/day.
• Dosages are usually less than 200 mcg/day.

Child dosage (ages 0–17 years):

The dosage is based on weight and thyroid hormone levels.

Senior dosage (ages 50 years and older):

• The typical starting dosage is 12.5–25 mcg/day.
• Your doctor will adjust your dosage every 6–8 weeks, based on your thyroid hormone lab results.

Dosage for goiter

Adult dosage (ages 18 years and older):

Your dosage is based on your needs and thyroid hormone levels. Your doctor will determine the right dosage for you and adjust it based on your current level of thyroid hormone.

Child dosage (ages 0–17 years):

There are no dosage recommendations for people younger than 18 years.

Dosage for thyroid cancer

Adult dosage (ages 18 years and older):

Your dosage is based on your needs and thyroid hormone levels. Your doctor will determine the right dosage for you and adjust it based on your current level of thyroid hormone.

Child dosage (ages 0–17 years):

There are no dosage recommendations for people younger than 18 years.

Dosage for special populations

For pregnant women: You may need a higher dosage of levothyroxine.

For people with heart disease:

• The recommended starting dosage is 12.5–25 mcg/day.
• Your dosage may be adjusted every 6–8 weeks.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always speak with your doctor or pharmacist about dosages that are right for you.

FDA warning: Not for obesity or weight loss

• This drug has a black box warning. This is the most serious warning from the Food and Drug Administration (FDA). A black box warning alerts doctors and patients about drug effects that may be dangerous.
• Thyroid hormones, including levothyroxine, should not be used for weight loss or to treat obesity. Taking doses that are higher than recommended can lead to serious or even life threatening effects.

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Vitamin supplements and antacids warning

Taking iron and calcium supplements or antacids can decrease the amount of levothyroxine your body absorbs. Do not take levothyroxine within 4 hours of taking these supplements or antacids.

Allergy warning

Levothyroxine can cause a severe allergic reaction. Symptoms can include:

• skin rash or hives
• flushing
• swelling of your face, lips, throat, or tongue
• trouble breathing
• wheezing
• stomach pain
• nausea
• vomiting
• diarrhea
• fever

If you develop these symptoms, call 911 or go to the nearest emergency room.

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal (cause death).

Food interactions warning

Certain foods, such as soybean flour, cotton seed meal, walnuts, and other dietary fibers, may affect how well your body absorbs levothyroxine.

Warnings for people with certain health conditions

For people with heart problems: Levothyroxine can increase your risk of serious heart problems, such as heart attack, abnormal heart rhythm, and heart failure. This risk is increased if you’ve already had these problems. Tell your doctor if you have heart problems or a history of heart problems. Your doctor may decide to start you on a lower dosage of levothyroxine.

For people with diabetes: Let your doctor know if you have diabetes. Taking levothyroxine can make your diabetes worse. Your doctor may monitor your blood sugar level more closely while you take this drug and adjust your diabetes drugs if needed.

For people with osteoporosis: Using levothyroxine for a long time can cause decreases in your bone mineral density and put you at higher risk of bone fractures.

For people with adrenal or pituitary gland problems: Let your doctor know if you have any adrenal or pituitary gland problems. Using levothyroxine can cause changes to your levels of thyroid hormone that could make these problems worse.

For people with blood clotting disorders: Let your doctor know if you have any blood clotting disorders. Taking levothyroxine may make it more difficult for your blood to clot and make bleeding more likely.

Warnings for other groups

For pregnant women: Studies of levothyroxine in pregnant women haven’t shown risk to the fetus. Talk to your doctor if you’re pregnant or planning to become pregnant. It appears unlikely that this drug will harm a pregnancy.

Not treating hypothyroidism could cause problems for both you and your pregnancy. You should not stop taking this drug during pregnancy.

For women who are breastfeeding: Small amounts of levothyroxine may pass into breast milk, but this drug is usually safe to take while breastfeeding. Talk to your doctor about the best way to feed your child while taking levothyroxine.

For seniors: If you’re older than 65 years, you may be at higher risk of developing negative heart effects (such as irregular heart rhythms) while taking this drug. Your doctor may choose to start you on a lower dosage.

For children: Levothyroxine has only been approved for use in children for the treatment of hypothyroidism. The tablet can be used safely in children of all ages.

Levothyroxine oral tablet is used for long-term treatment. It comes with serious risks if you don’t take it as prescribed.

If you stop taking the drug or don’t take it at all: Your thyroid hormones will remain low, which may result in low energy levels, tiredness, weakness, slower speech, constipation, or thickened skin. It may even lead to coma.

If you miss doses or don’t take the drug on schedule: Your medication may not work as well or may stop working completely. For this drug to work well, a certain amount needs to be in your body at all times.

If you take too much: You could have dangerous levels of the drug in your body. Symptoms of an overdose can include:

• confusion
• disorientation
• stroke
• shock
• coma

If you think you’ve taken too much of this drug, call your doctor or local poison control center. If your symptoms are severe, call 911 or go to the nearest emergency room right away.

What to do if you miss a dose: Take your dose as soon as you remember. But if you remember just a few hours before your next scheduled dose, take only one dose. Never try to catch up by taking two doses at once. This could result in dangerous side effects.

How to tell if the drug is working: You should feel your symptoms of low thyroid hormone decrease. For instance, you should have more energy, less tiredness, and less weakness.

Keep these considerations in mind if your doctor prescribes levothyroxine for you.

General

• Take levothyroxine without food, on an empty stomach.
• Take levothyroxine in the morning. Take it 30 minutes to 1 hour before your first meal of the day.
• You can cut or crush the tablet.

Storage

• Store levothyroxine at room temperature between 59°F and 86°F (15°C and 30°C).
• Keep it away from light.
• Don’t store this medication in moist or damp areas, such as bathrooms.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

• Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
• Don’t worry about airport X-ray machines. They can’t harm your medication.
• You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled container with you.
• Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

Clinical monitoring

Your doctor will monitor your thyroid hormone levels during your treatment with this drug. Your doctor will have blood tests done to make sure your thyroid hormone level is within the range they feel is best for you. The tests will tell if your medication is working.

Your diet

Certain foods (such as soybean flour, cotton seed meal, walnuts, and other dietary fibers) may affect how well your body absorbs levothyroxine. Talk to your doctor about whether you should make any changes to your diet.

Prior authorization

Many insurance companies require a prior authorization for certain brand-name forms of this drug. This means your doctor will need to get approval from your insurance company before your insurance company will pay for the prescription.

There are other drugs available to treat your condition. Some may be better suited for you than others. Talk to your doctor about other drug options that may work for you.

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.

Free thyroxine (T4 free)

Thyroxine (T4) is one of the two main thyroid hormones, the main function of which is the regulation of energy and plastic metabolism in the body. Free thyroxine is the biologically active part of total thyroxine, which plays an important role in metabolism.

Synonyms Russian

Free T4, free tetraiodothyronine.

Synonyms English

Thyroxine, Free T4.

Research method

Electrochemiluminescent immunoassay.

Detection range: 1.3 – 100 pmol/L.

Units

pmol/l (picomole per liter).

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.

General information about the study

During the analysis, the concentration in the blood of the fraction of the main thyroid hormone, thyroxine (T4), that is not associated with proteins, is determined. This is one of the most important tests for assessing thyroid function, its results do not depend on the concentration of thyroxine-binding proteins in the blood plasma, and allow you to detect the level of only the active part of the hormone. Most often, this test is prescribed in conjunction with measuring the concentration of thyroid-stimulating hormone (TSH), a regulator of thyroid function. The thyroid gland controls metabolism and the intensity of energy consumption by the body. It works by a feedback mechanism with the pituitary gland. The pituitary gland secretes thyrotropin (TSH) in response to a decrease in the concentration of thyroxine (T4), thereby stimulating the thyroid gland to produce hormones. When the level of thyroxine rises, the pituitary gland begins to produce less thyroid-stimulating hormone and the secretion of thyroxine by the thyroid gland decreases.

Thyroxine (T4) makes up about 90% of the total amount of hormones secreted by the thyroid gland. T4 is found in the blood either free or bound to globulin proteins. The main part of all thyroxine is in bound form and only 0.1% is in free form. It is the free fraction of the T4 hormone that is the most biologically active.

If the thyroid gland is not able to produce the required amount of thyroxine, or insufficient thyroid-stimulating hormone is produced to stimulate it, symptoms of hypothyroidism appear. In patients with a low level of T4, body weight increases, the skin dries, fatigue increases, they become very sensitive to cold, and the menstrual cycle is disturbed in women. If the level of free T4 is higher than normal, the metabolic processes in the body and the production of energy in cells increase, which leads to hyperthyroidism, which is characterized by rapid heartbeat, anxiety, weight loss, sleep disturbance, trembling hands, dry and red eyes, puffiness of the face .

The most common cause of thyroid hormone imbalance is an autoimmune disease of the gland. This can be Basedow’s disease (causes hyperthyroidism with elevated free T4) or Hashimoto’s thyroiditis (causes hypothyroidism – free T4 is low).

What is research used for?

• For diagnosing thyroid disorders and monitoring their treatment.
• For diagnosing the causes of female infertility.
• For the diagnosis of congenital hypothyroidism.

When is the test scheduled?

• Symptoms of hyperthyroidism: palpitations, irritability, weight loss, insomnia, hand tremors, weakness, fatigue, diarrhea (in some cases), increased sensitivity to light, blurred vision, puffiness around the eyes, dryness, redness, protrusion of the eyeballs.
• With symptoms of hypothyroidism: weight gain, dry skin, constipation, cold intolerance, swelling, hair loss, irregular menstruation in women. With advanced hypothyroidism, complications such as heart rhythm disturbance, ischemia of the heart muscle, and coma can develop. In children, hypothyroidism sometimes causes a delay in physical and mental development – cretinism.
• At a preventive (for example, annual) examination, together with other laboratory tests (general blood and urine tests, various biochemical parameters).
• To control the treatment of thyroid diseases – periodically, together with the study of thyroid-stimulating hormone (at least 1 time in 3 months).
• Pregnant women, predisposed to thyroid diseases or suffering from them – for the timely detection of violations of the secretion of thyroid hormones (they can lead to abortion or congenital pathology of the fetus).
• In the first days of life, newborns born to mothers with thyroid diseases.

What do the results mean?

Reference values ​​

During pregnancy

Causes of increased free T4 level

• Diffuse toxic goiter.
• Thyroiditis.
• Thyroid adenoma.
• TSH-independent thyrotoxicosis.
• Obesity.
• Postpartum thyroid dysfunction.
• Diseases of the kidneys.
• Chronic liver pathology (hepatitis, cirrhosis, etc.).
• Heparin therapy.

Causes of a decrease in the level of free T4

• Primary hypothyroidism.
• Endemic goiter.
• Autoimmune thyroiditis.
• Thyroid resection.
• Secondary hypothyroidism.
• Thyrotropinoma.
• Inflammatory processes in the pituitary gland and hypothalamus.
• Iodine deficiency.
• Protein deficiency (wasting).
• Lead poisoning.
• Heroin addiction.
• Taking oral contraceptives.

What can influence the result?

• Thyroxine levels may be elevated when taking the following drugs: amiodarone, levothyroxine, propranolol, propylthiouracil, aspirin, danazol, furosemide, tamoxifen, valproic acid.
• Anabolic steroids, phenytoin, carbamazepine, antithyroid drugs, clofibrate, lithium preparations, methadone, octreotide can reduce thyrcosine levels.

Also recommended

• Thyroid stimulating hormone (TSH)
• Triiodothyronine free (T3 free)

Who orders the examination?

Endocrinologist, internist, pediatrician, gynecologist, neuropathologist, surgeon.

Total triiodothyronine (T3)

Triiodothyronine (T3) is one of the two main thyroid hormones, the main function of which is the regulation of energy (mainly oxygen uptake by tissues) and plastic metabolism in the body. Total triiodothyronine is the sum of two fractions: bound and not bound to plasma proteins.

Synonyms Russian

T3 general.

Synonyms English

Total Triiodthyronine, TT3.

Test method

Immunochemiluminescent assay.

Detection range: 0.3 – 10 nmol/L.

Units

Nmol/l (nanomoles per liter).

What biomaterial can be used for research?

Venous blood.

How to properly prepare for an examination?

1. Do not eat for 2-3 hours before the test, you can drink pure non-carbonated water.
2. Avoid taking steroid and thyroid hormones 48 hours before the study (as agreed with the doctor).
3. Exclude physical and emotional overexertion 24 hours before the study.
4. Do not smoke for 3 hours prior to the study.

General information about the study

Triiodothyronine (T3) is a thyroid hormone whose biological activity is 3-5 times higher than that of thyroxine (T4). A certain amount of triiodothyronine is synthesized in the thyroid gland, but it is mainly formed during the deiodination of thyroxine outside it. Most of the triiodothyronine circulating in the blood is associated with plasma proteins, in particular with thyroxine-binding globulin, thyroxine-binding prealbumin and albumin. The remaining share (less than 1%) of triiodothyronine is a biologically active (free) fraction.

Triiodothyronine regulates the rate of oxygen consumption by tissues, stimulates protein synthesis, gluconeogenesis and glycogenolysis (which leads to an increase in blood glucose concentration), lipolysis, intestinal motor function, enhances catabolism and excretion of cholesterol with bile, promotes the synthesis of vitamin A and absorption of vitamin in the intestine B ₁₂ , bone growth, production of sex hormones. Children need this hormone for growth and development of the central nervous system.

What is research used for?

For the diagnosis and monitoring of triiodothyronine-related thyrotoxicosis and hypothyroidism.

When is the test ordered?

• When the level of TSH is low with a normal content of free thyroxine (T4).
• For symptoms of hyperthyroidism (thyrotoxicosis) and normal free thyroxine levels
  • Symptoms of hyperthyroidism:
    • palpitations,
    • increased irritability,
    • weight loss,
    • insomnia,
    • hand shake,
    • weakness, fatigue,
    • diarrhea,
    • hypersensitivity to light,
    • visual impairment,
    • puffiness around the eyes, their dryness, redness, exophthalmos (“protrusion” of the eyeballs).
  • Symptoms of hypothyroidism:
    • weight gain,
    • dry skin,
    • constipation,
    • cold intolerance,
    • edema,
    • dryness, hair loss,
    • irregular menstruation in women.
• With an asymptomatic increase in T4 (which can sometimes occur with euthyroidism, in such cases, an increase in thyroxin is associated with a change in the concentration of thyroxin-binding globulin).

What do the results mean?

Reference

Reasons for the increase in total T3:

• hyperthyroidism,
• isolated triiodothyronine due to thyrotoxicosis,
• TSH-independent thyrotoxicosis,
• Graves’ disease,
• thyroiditis,
• postpartum thyroid dysfunction,
• thyroid adenoma,
• nephrotic syndrome,
• thyroid hormone resistance syndrome,
• Pendred’s syndrome.

Reasons for the decrease in total T3:

• hypothyroidism,
• acute and subacute thyroiditis,
• postoperative conditions and severe diseases,
• decreased level of thyroxin-binding globulin,
• anorexia nervosa,
• cirrhosis of the liver,
• kidney failure,
• iodine deficiency (severe),
• thyroidectomy,
• pre-eclampsia and eclampsia,
• treatment with radioactive iodine isotopes.

What can influence the result?

Reducing the concentration of triiodothyronine is facilitated by taking amiodarone, anabolic steroids, androgens, dexamethasone, propranolol, salicylates, coumarin derivatives, antithyroid drugs, aspirin, atenolol, carbamazepine, cimetidine, furosemide, lithium preparations, theophylline.

Estrogens, contraceptives, methadone, amiodarone (rarely), clofibrate, tamoxifen, phenothiazines, terbutaline, valproic acid, lithium preparations, antithyroid drugs, rifampicin can lead to an increase in the concentration of triiodothyronine.

Falsely high values ​​of triiodothyronine can be observed during pregnancy, myeloma, and also in severe liver diseases (due to an increase in the concentration of thyroxin-binding globulin in the blood plasma).

Important notes

Elderly people and patients with severe somatic diseases may suffer from low TK syndrome – this is a decrease in the level of triiodothyronine in the blood serum with a normal content of T4. In such people, this is not a sign of hypothyroidism.

Also recommended

• Triiodothyronine free (T3 free)
• Free thyroxine (T4 free)
• Thyroid Stimulating Hormone (TSH)
• Anti-thyroglobulin antibodies (anti-TG)
• Thyroid peroxidase antibodies (anti-TPO)

Who orders the examination?

Endocrinologist, internist, general practitioner.

Literature

1. Lifshitz V.M. Biochemical analyzes in the clinic: a reference book / V.