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Which Blood Test For Thyroid Levels

Mild Hypothyroidism: Who Should Be Treated

TSH test explained | Thyroid stimulating hormone test | Thyroid function test | Blood TSH test

What to do about mild hypothyroidism is a subject that has been studied and debated for years. Mild hypothyroidism is also called subclinical hypothyroidism. It doesnt meet the standard definition of overt hypothyroidism. You may have no symptoms, and your thyroid function blood tests show a mixed picture.

Your free T4 level is normal, meaning your body is getting enough thyroid hormone. It is your TSH level that is above the normal range, which indicates your thyroid gland has to work harder to pump out that thyroid hormone.

One worry about mild hypothyroidism is the potential link between untreated subclinical hypothyroidism and coronary artery disease. Results of research on whether subclinical thyroid disease causes heart problems have been conflicting. However, the condition has been associated with heart and blood vessel abnormalities, and some studies suggest that treating mild hypothyroidism can improve various markers of heart structure and function.

However, there are potential downsides to treating subclinical hypothyroidism. There is the risk of overtreatment, which might cause symptoms, such as feeling jittery and insomnia. Also, long-term overtreatment can lead to loss of bone density.

If your TSH level is higher than 10 mIU/L, you should start treatment, because you will develop symptoms of an underactive thyroid, even if you dont have them now.

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What Do Thyroid Antibodies Tell You

Three antibodies related to autoimmune thyroid diseases can tell what type of autoimmune disease a person has, and how severe or advanced it might be.

  • Anti-thyroglobulin High levels of TgAb are present in 8 in 10 patients with Hashimotos and in 4 in 10 of people being diagnosed with Graves disease.
  • Anti-thyroperoxidase High levels of TPOAb are found in 9 in 10 patients with Hashimotos and 8 in 10 of patients with Graves disease.
  • Anti-TSH receptor High levels of TRAb are found in 9 in 10 patients with Graves disease and in less than 2 in 10 patients with Hashimotos.

Its important to note that high levels of either TgAb or TPOAb can be found in 1 in 10 of people without an autoimmune thyroid disease, as well as in 2 in 10 of people that are considered healthy.

Theres also a small percentage of people with autoimmune diseases who have no antibodies detected.

TPOAb testing in early pregnancy can predict if a person is at risk of developing postpartum thyroiditis. Postpartum thyroiditis occurs in about 1 in 10 people after giving birth. About 5 in 10 of pregnant people with high TPOAb will develop postpartum thyroiditis .

TgAb or TPOAb are found in 1 in 10 healthy people, more likely females and elderly people .

Is Tsh Over 25 Indicative Of Disease

Sometimes.

1 in 10 of people with TSH values above 3.0 mIU/L has Hashimotos .

TSH itself, as a marker of disease is not enough. If you have any symptoms connected to thyroid, talk to your health provider and get the full thyroid blood work done. This is the best first step towards understanding the health of your thyroid.

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What Are Thyroid Hormones

The thyroid gland produces hormones that are essential for normal body metabolism. Blood testing is now commonly available to determine the adequacy of the levels of thyroid hormones. These blood tests can define whether the thyroid gland’s hormone production is normal, overactive, or underactive.

The thyroid gland is located in the lower part of the neck, below the Adam’s apple.The gland wraps around the windpipe and has a shape that is similar to a butterfly – formed by two wings and attached by a middle part .

The thyroid gland uses iodine to produce thyroid hormones.

  • The two most important thyroid hormones are thyroxine and triiodothyronine , which account for 99.9% and 0.1% of thyroid hormones present in the blood respectively.
  • However, the hormone with the most biological activity is T3.
  • Once released from the thyroid gland into the blood, a large amount of T4 is converted into T3 – the active hormone that affects the metabolism of cells.

Is There Anything Else I Should Know

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The sensitivity and specificity of thyroid antibody testing is improving but is still not as good as health practitioners would like it to be. All of the thyroid antibody tests have changed over time. This is part of the reason that the tests have historically acquired many different names. There are also many distinct methodologies and each has different reference ranges. If someone is having several tests done at regular intervals for monitoring purposes, it is best to have test done by the same laboratory each time, using the same methodology.

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T3 And T4 Interpretations

  • A normal TSH and normal T4 indicates a normally functioning thyroid gland.
  • A low TSH and high T4 generally indicates hyperthyroidism.
  • A high TSH and low T4 indicates primary hypothyroidism .
  • A low TSH and low T4 suggest secondary hypothyroidism .

For diagnostic purposes, a low T3 value accompanied by a high TSH value is considered evidence of hypothyroidism. By contrast, a low TSH value accompanied by a high T3 value is considered evidence of hyperthyroidism.

Diagnosis Of Tsh Levels

If a person shows symptoms of a thyroid disorder, his or her doctor will most likely require a TSH test. The TSH test determines the level of TSH in the body, as well as T3 and T4 hormone levels too. It is the best way to know if one has a thyroid problem.

The TSH Levels Test is used to:

  • Identify if the person has a thyroid disorder, such as hypothyroidism or hyperthyroidism, especially if the person has shown symptoms of either beforehand
0Confused about your recent thyroid test? Here is some information on TSH range.

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What Is Thyroid Medication

Thyroid Hormone Treatment Levothyroxine is thestandard of care in thyroid hormone replacement therapy and treatment of hypothyroidism. Levothyroxine is equivalent to the T4 form of naturally occurring thyroid hormone and is available in generic and brand name forms.

How do I take levothyroxine? To optimize absorption of your thyroid medication, it should be taken with water at a regular time each day. Multiple medications and supplements decrease absorption of thyroid hormone and should be taken 3-4 hours apart, including calcium and iron supplements, proton pump inhibitors, soy, and multivitamins with minerals. Because of the way levothyroxine is metabolized by the body, your doctor may ask you to take an extra pill or skip a pill on some days of the week. This helps us to fine tune your medication dose for your body and should be guided by an endocrinologist.

For patients with celiac disease or gluten sensitivity, a gluten free formulation of levothyroxine is available.

Some individuals may have genetic variant that affects how the body converts T4 to T3 and these individuals may benefit from the addition of a small dose of triiodothyronine.

Liothyronine is replacement T3 thyroid hormone. This medication has a short half-life and is taken twice per day or in combination with levothyroxine. Liothyronine alone is not used for treatment of hypothyroidism long term.

What Other Tests May Be Ordered In Addition To A Thyroid Panel

Thyroid Test | Normal Thyroid Levels | Optimal Thyroid Levels | T3 vs T4

Blood tests that may be performed in addition to a thyroid panel may include:

  • Thyroid antibodies – to help diagnose autoimmune thyroid disease and distinguish it from other thyroid conditions
  • Calcitonin – to help diagnose C-cell hyperplasia and medullary thyroid cancer
  • Thyroglobulin – primarily to monitor treatment and recurrence of thyroid cancer
  • Thyroxine-binding globulin – to evaluate patients with abnormal T4 and T3 levels

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Are There Any Other Tests For The Diagnosis Of Hyperthyroidism

The vast majority of cases of hyperthyroidism are diagnosed by the combination of clinical history, initial laboratory screening tests, and the determination of T4 or fT4 blood concentrations.

On rare occasions, additional tests such as the T3 suppression test or advanced imaging studies of the thyroid gland may need to be performed. Imaging studies are usually done at a referral center.

Contributors: Krista Williams, BSc, DVM; Kristiina Ruotsalo, DVM, DVSc, Dip ACVP; Margo S. Tant BSc, DVM, DVSc

Why You May Need A Thyroid Test

Women of all ages are more likely than men to have low thyroid hormone levels. However, many of their symptoms are attributed to other conditions or written off as a consequence of aging.

A blood test for levels of TSH is the most sensitive test for determining whether you have hypothyroidism. Most laboratories use 0.45 5.00 mIU/L as a normal reference range for TSH. People with TSH between 5.00 and 9.99 mIU/L often have no symptoms , but some do. Another test called T4 will be done if your TSH is in this range. A low level of T4 usually means you will benefit from thyroid hormone replacement.

Many people with hypothyroidism or subclinical hypothyroidism aren’t aware anything is wrong because they haven’t been tested. The U.S. Preventive Services Task Force doesn’t recommend thyroid screening because it hasn’t found sufficient evidence that testing thyroid hormone levels in large groups of people without symptoms is cost-effective. Dr. Garber agrees, and suggests a different approachtesting asymptomatic people who are most likely to develop thyroid disease and benefit from treatment.

Treating subclinical hypothyroidism with synthetic thyroid hormone may reduce the risk of developing more serious problems like cardiovascular disease. They note that low thyroid hormone can cause a high cholesterol level and treatment with thyroid hormone may make statin therapy unnecessary.

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Controversy Over Optimal Tsh

While most laboratories define a normal TSH as between roughly 0.5 mU/l and 5.0 mU/l, some experts argue that the upper limit of a normal TSH should be loweraround 2.5 mU/l.

The reasoning behind this is that the vast majority of adults without thyroid disease have a TSH value between 0.45 and 4.12 mU/l.

In addition, some physicians believe older patients should have a TSH level that is greater than 4.0 mU/l or 5.0 mU/l, since TSH normally increases with age.

Doctors can avoid some of this controversy simply by looking at each person as an individual. For example, a person who still has significant symptoms of hypothyroidism at a TSH of 4.0 mU/l may do better with a goal TSH of around 1.0 mU/l.

In contrast, someone who has health riskssuch as heart disease or osteoporosismay benefit from having a goal TSH that is higher, perhaps around 5.0 mU/l or 6.0 mU/l.

In pregnancy, TSH should not be allowed to rise above 3.0 mU/l for the health of both the baby and mother.

How Does A Blood Test For Hyperthyroidism Work

7 Causes Behind Low Thyroid Function

A TSH test for hyperthyroidism evaluates your levels of thyroid-stimulating hormone , and the thyroid hormones T3 and T4 may also be evaluated. Because TSH signals the thyroid gland to produce more thyroid hormones, unusually low levels of TSH can mean that your thyroid is making too many hormones. T3 and T4 measurements can also reveal just how high your thyroid hormone levels are, which can help your healthcare provider decide on a treatment strategy.

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What Is Being Tested

Thyroid autoantibodies are antibodies that develop when a persons immune system mistakenly targets components of the thyroid gland or thyroid proteins, leading to chronic inflammation of the thyroid , tissue damage, and/or disruption of thyroid function. Laboratory tests detect the presence and measure the quantity of specific thyroid autoantibodies in the blood.

The thyroid is a small, butterfly-shaped gland that

Thyroid autoantibodies are antibodies that develop when a persons immune system mistakenly targets components of the thyroid gland or thyroid proteins, leading to chronic inflammation of the thyroid , tissue damage, and/or disruption of thyroid function. Laboratory tests detect the presence and measure the quantity of specific thyroid autoantibodies in the blood.

The thyroid is a small, butterfly-shaped gland that lies flat against the windpipe in the throat. The primary hormones that it produces, thyroxine and triiodothyronine , are vital in helping to regulate the rate at which the body uses energy . The body uses a feedback system;in which thyroid stimulating hormone stimulates the thyroid to produce T4 and T3 as needed. This system helps maintain a relatively stable amount of the thyroid hormones in the blood. When thyroid antibodies interfere with this process, they can lead to chronic conditions and autoimmune disorders associated with hypothyroidism or hyperthyroidism, such as Graves disease or Hashimoto thyroiditis.

Thyroid antibody tests include:

What Is Reverse T3

Reverse T3 is a biologically inactive form of T3. Normally, when T4 is converted to T3 in the body, a certain percentage of the T3 is in the form of RT3. When the body is under stress, such as during a serious illness, thyroid hormone levels may be outside of normal ranges even though there is no thyroid disease present. RT3 may be elevated in non-thyroidal conditions, particularly the stress of illness. It is generally recommended that thyroid testing be avoided in hospitalized patients or deferred until after a person has recovered from an acute illness. Use of the RT3 test remains controversial, and it is not widely requested.

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When Should I Get A T3 Test

People will usually have a free or total T3 test when their doctor suspects they have a thyroid problem. This may be because they had an abnormal TSH test result, or it may be because they are experiencing symptoms of an overactive thyroid, called hyperthyroidism. Symptoms of hyperthyroidism may include:

  • Weight changes, usually weight loss
  • Fatigue
  • Nervousness or anxiety
  • Problems with concentration

Although it may be used sometimes, T3 is less helpful in diagnosing hypothyroidism, because T3 is typically the last hormone to become abnormal in hypothyroid patients.

Medical History And Physical Exam

Been Told Your TSH Thyroid Levels Are “Normal” Think Again

If you have any signs or symptoms that suggest you might have thyroid cancer, your health care professional will want to know your complete medical history. You will be asked questions about your possible risk factors, symptoms, and any other health problems or concerns. If someone in your family has had thyroid cancer or tumors called pheochromocytomas, it is important to tell your doctor, as you might be at high risk for this disease.

Your doctor will examine you to get more information about possible signs of thyroid cancer and other health problems. During the exam, the doctor will pay special attention to the size and firmness of your thyroid and any enlarged lymph nodes in your neck.

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Hypothyroidism Caused By Decreased Tbg

Low levels of TBG cause free thyroid hormone levels to rise because there are fewer proteins available to bind thyroid hormones. The high circulating levels of T4 and T3 induce cellular resistance to thyroid hormone, much like how cells develop insulin resistance upon continuous exposure to high levels of insulin. This problem means that even though there is plenty of thyroid hormone, cells cant use it. As a result, symptoms of hypothyroidism develop. Patients with this pattern of thyroid dysfunction have normal TSH and T4, high T3, low T3 uptake, and low TBG.

Low TBG can be caused by a high testosterone level. This thyroid pattern often occurs in women with PCOS and insulin resistance because these two conditions lead to elevated testosterone. Insulin sensitivity and blood sugar balance need to be restored to treat this pattern of thyroid dysfunction.

Tsh Levels During Pregnancy

Thyroid hormones can affect brain and nervous system development of the baby, especially during the first trimester. At around 12 weeks, the baby will start to produce thyroid hormones of its own. Until then, the baby is entirely dependent on the transfer of thyroid hormones from the mother.

Both hypothyroidism and hyperthyroidism can occur during pregnancy. You may also have one of these conditions prior to getting pregnant and not know it.

Untreated thyroid disease can cause miscarriage, premature birth, or low birth weight. It can also cause preeclampsia. Having an underactive thyroid during pregnancy can also affect the babys growth and brain development.

Its important to have your TSH levels checked during pregnancy to make sure that both you and your baby remain healthy.

Hormones secreted during pregnancy can affect TSH levels, altering them from your typical numbers.

This chart provides an overview of normal, low, and high TSH levels for pregnant women who are between 18 and 45 years old:

Normal

Having a doctor monitor your thyroid gland and its production of thyroid hormones is the only way to comprehensively determine thyroid health.

The thyroid is one of several glands and structures that make up the bodys endocrine system.

It works in partnership with the pituitary and hypothalamus glands. These glands stimulate the thyroid to secrete two hormones, which are then released into the bloodstream: T4 and T3.

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When Should I Get T4 Testing

There are a number of different reasons why a doctor might order a T4 test. Often it is ordered to follow up on an abnormal TSH test result.

It may also be used when a patient has symptoms that may be related to a thyroid disorder. Underactive thyroid and overactive thyroid are both common diseases. If you are having symptoms of these disorders, your doctor may order a T4 test in combination with other thyroid function tests, such as TSH and T3. This series of tests is also called a thyroid panel.

Hypothyroidism affects nearly 5% of adolescents and adults in the United States. Symptoms of hypothyroidism may include:

  • Fatigue
  • Rapid or irregular heartbeat
  • Loose, frequent bowel movements

There are additional reasons why a doctor might check a patients T4, such as monitoring the effectiveness of treatment with replacement thyroid hormones, screening newborns for congenital hypothyroidism, and to evaluate possible problems with the hypothalamus or pituitary gland.

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