The Pituitary Gland

What is T3 and T4

The thyroid gland produce two major hormones called Triiodothyronine (T3) and Thyroxine (T4). The thyroid gland takes iodine, found in our diet, combines it with an amino acid, tyrosine and converts it into T3 and T4.

  • T3 – Triiodothyronine: Containing three iodine atoms.
  • T4 – Thyroxine: Containing four iodine atoms
T3 Triiodothyronine Image
T4 Thyroxine Image

The Follicular cells are the major cell type in the thyroid gland and are responsible for the production and secretion of the thyroid hormones T3 and T4.

T3 (triiodothyronine): Approximately 20% of T3 is secreted into the bloodstream directly by the thyroid gland. The remaining 80% is produced by the removal of one iodine atom from T4 by a process called deiodination. This process occurs primarily in organs such as the liver and kidneys. T3 is the active form of the thyroid hormone T4 (thyroxine).

T4 (thyroxine): functions as a “storage” hormone. On its own, it is unable to produce energy. Therefore, it must undergo a process known as deiodination in which it loses an atom of iodine to become triiodothyronine (T3).

Both triiodothyronine (T3) and thyroxine (T4) are essential hormones for brain and physical development in infants and for metabolic activity in adults. Thyroid hormones help the brain, heart, liver, muscles, and other organs function properly.

How is T3 and T4 controlled?

The production and release of T3 and T4 is controlled by thyroid stimulating hormone (TSH) secreted by the pituitary gland, which is in turn regulated by thyrotropin-releasing hormone (TRH) secreted by the hypothalamus (a small region of the brain).

Negative Feedback Loop Image
Negative Feedback Loop

This process works as a negative feedback loop. When levels of T3 and T4 decrease below normal, the pituitary gland produces TSH, stimulating the thyroid gland to produce more hormones (T3 and T4). Once the levels rise, the pituitary gland then decreases TSH production.

Hence, this system allows the body to maintain a constant level of T3 and T4 in the body. 

Forms of T3 and T4 hormones.

Most of the T3 and T4 in your body are bound to serum protein such as ( thyroxine-binding globulin (TBG), transthyretin (TTR), albumin, and lipoproteins) and transported throughout the body.

However, a smaller portion of T3 and T4 doesn’t bind to protein is called Free T3 (FT3) & Free T4 (FT4), which circulates through the bloodstream as free or unbound hormones.

T3 exists in two forms in the blood:

  • Bound T3: More than 99.5% of T3 are bound to serum proteins that help transport the hormone through the body.
  • Free or Unbound T3: About 0.5% of T3 doesn’t bind to serum protein is called free T3 and circulates unbound in your blood.

T4 exists in two forms in the blood:

  • Bound T4: More than 99.95% of T4 are bound to serum proteins.
  • Free or Unbound T4: A minimal amount, about 0.02%, of T4 doesn’t bind to serum protein is called free T4 and circulates unbound in your blood.

Why doctors perform T3 and T4 tests

Blood tests for thyroid function such as T3, T4, TSH and others are an important part of diagnosing and treating thyroid disorders. Some conclusions can be drawn from a single test, however a combination of two or more tests are usually needed to check the health of your thyroid.

By comparing the values of different thyroid tests, a doctor can determine whether a person has hypothyroidism  (low thyroid function), hyperthyroidism (overactive thyroid), or an autoimmune thyroid disease such as Graves’ disease or Hashimoto’s thyroiditis.

T3 (triiodothyronine) Test

T3 (triiodothyronine) is a thyroid hormone and the test measures how much is in your blood.

  • Total T3 test: This test simply measures how much of T3 hormone both (bounded and free) is present in your blood. If the level is either abnormally high or abnormally low, it can be an indicator of thyroid disease.
  • Free T3 test: This test just measures free or unbounded T3 present in your blood. This test is often not reliable and therefore not typically helpful.
  • Reverse T3 test: Reverse T3 (RT3) is a biologically inactive protein that is structurally very similar to T3, but the iodine atoms are placed in different locations, which makes it inactive. RT3 is a blood test that not commonly ordered by the doctors.
Reverse T3 Image

What does T3 test results mean?

This single test may not give your doctor any definitive answers about what is wrong. However, abnormal results can help point them in the right direction. If your results show high T3 levels, it may mean you have hyperthyroidism (overactive thyroid). Low T3 levels may mean you have hypothyroidism, a condition in which your body doesn’t make enough thyroid hormone.

However, T3 tests are generally more useful for diagnosing hyperthyroidism than hypothyroidism.

Further, T3 tests are frequently ordered with T4 and TSH (thyroid stimulating hormone) tests, because it can give your doctor a more complete picture of what’s going on.

If you have questions about your results, talk to your health care provider.

T4 (thyroxine) Test

T4 (thyroxine) is a thyroid hormone and the test measures how much is in your blood.

The T4 test measures two key values:

  • Total T4 test: This test measures how much of T4 hormone (both bounded and free) is present in your blood. 
  • Free T4 test: This test just measures free or unbounded T4 present in your blood. A free T4 test is often preferred over a total T4 test.

What does T4 test results mean?

Your results may come in the form of total T4, free T4. High levels of any of these tests (total T4, free T4) may indicate an overactive thyroid, also known as hyperthyroidism. Low levels of any of these tests (total T4, free T4) may indicate an underactive thyroid, also known as hypothyroidism.

Therefore, if your T4 test results are not normal, your health care provider will likely order more thyroid tests to help make a diagnosis. These may include:

  • T3 thyroid hormone tests.
  • A TSH (thyroid stimulating hormone) test.
  • Tests to diagnose Graves’ disease, an autoimmune disease that causes hyperthyroidism.
  • Tests to diagnose Hashimoto’s thyroiditis, an autoimmune disease that causes hypothyroidism.

How do I get ready for T3 and T4 test?

It’s important to tell your doctor about all of the medications you’re currently taking, as some may affect your T3, T4 test results. If your doctor knows about your medications in advance, they can advise you to temporarily stop using them or consider their effect when interpreting your results.
Some medications that can affect your T3, T4 levels include:

  • Thyroid related drugs
  • Steroids
  • Birth control pills or other medications containing hormones, such as androgens and estrogens etc.

In addition, you may also need to fast (not eat or drink) for several hours before the test. Your health care provider will let you know if there are any special instructions to follow.

Procedure for T3, T4 test

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial (a small glass or plastic bottle).

Blood sample from a vein Image
Blood sample from a vein

You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Note: A normal T3 test result doesn’t necessarily mean that your thyroid is functioning perfectly. Measuring your T4 and TSH can help your doctor figure out if you have a thyroid problem despite a normal T3 result.

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What is an Endocrinologist

An endocrinologist is a specially trained doctors who is qualified to diagnose diseases that affect the hormone making glands. The conditions that are treated by an endocrinologist are as following:

  • Thyroid diseases
  • Diabetes
  • Hypertension
  • Menopause
  • Over or under production of hormones
  • Lack of growth
  • Metabolic disorders
  • Lipid disorders
  • Cancers of the endocrine glands
  • Osteoporosis

The common diseases and disorders that endocrinologists deal with include diabetes and thyroid disorders.

Endocrinologist Image

An Endocrinologist is a True Specialist

An endocrinologist is a specialist who has thoroughly studied hormonal conditions and knows the best possible treatments, even when conventional treatments do not work well. Unlike a family doctor or general practitioner, an endocrinologist studies hormones and hormonal diseases in depth. Hence, this specialist will be able to provide the best possible treatment. 

What to expect at your first appointment with an endocrinologist

Your endocrinologist is likely to ask you a number of questions. So being prepared before you see him will be of great help to you, as this may save time to go over any particularly important points you feel the need to spend more time on.

He will ask in detail about the symptoms you are experiencing, specifically related to the deficiency or excess of a hormone you may have.

Your doctor may ask:

  • What are your symptoms, and when did you first notice them?
  • How have your symptoms changed over time?
  • Has your appearance changed, including your weight or the amount of your body hair?
  • Have any of your family members been diagnosed with thyroid disease, hormonal or autoimmune conditions?
  • Are you currently being treated or have you recently been treated for any other medical conditions?
  • Have you recently had a baby?
  • Have you lost interest in sex? If you’re a woman, has your menstrual cycle changed?
  • Have you had any recent head injuries or have you had neurosurgery?

Further, your examination will depend on the type of problem you have. Your endocrinologist will look for signs of a disease as well as complications of the disease and treatments.

An Endocrinologist Works with Your Primary Care Doctor

Visiting an endocrinologist does not mean you will never see your primary care doctor again. Going to an endocrinologist when struggling with a hormonal condition gives you another set of eyes to ensure your health is as good as it can be.

Remember, your goal when facing a hormonal disease diagnosis should be to take care of your disease as best as possible. This is often done with the support of an endocrinologist. 

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Hashimoto’s Disease

Hashimoto’s Disease

Hashimoto’s Disease is an autoimmune disorder in which the immune system mistakenly attacks the thyroid gland. This can lead to hypothyroidism, a condition in which thyroid does not make enough hormones for body’s need. Hashimoto is the most common cause of hypothyroidism (an underactive thyroid).

Generally immune system protects body against bacteria and viruses. But in Hashimoto’s Disease, immune system make antibodies, which attacks the cells of thyroid gland. Doctors do not know why this happens, but some scientists believe genetic factors may be involved. The disease affects more women than men.

Causes of Hashimoto’s Disease

The exact cause of the disease is not known, but many factors are believed to play a role:

Genetic: You are at higher risk of Hashimoto’s disease, if others in your family have thyroid disease or other autoimmune disorder. This suggests a genetic component to the disease.

Hormones: It is seven times more likely to occur Hashimoto’s Disease in women than men. Furthermore, some women have thyroid problems during the first year after having a baby called postpartum thyroiditis. Although the problem usually goes away, but some of these women develop Hashimoto’s years later.

Radiation exposure. People exposed to excessive levels of environmental radiation are more prone to Hashimoto’s disease.

Age. Hashimoto’s disease can occur at any age but more commonly occurs during middle age.

Symptoms of Hashimoto’s disease

You may have Hashimoto’s disease for many years before you experience any symptoms. The disease can progress for a long time, before it causes noticeable thyroid damage. The first sign is often an enlarged thyroid, called a goiter. The goiter may cause the front of your neck to look swollen. You may feel it in your throat, or it may be hard to swallow. Other sign and symptoms of an underactive thyroid due to Hashimoto’s may include:

  • Constipation
  • Dry, pale skin
  • Hoarse voice
  • Depression
  • Inability to get warm
  • Joint and muscle pain
  • Hair loss
  • Irregular menstrual periods
  • Slowed heart rate
  • Puffiness of the face
Hashimoto's Disease Symptoms

Because the symptoms of Hashimoto’s thyroid may be similar to those for other medical conditions, it is important to see your doctor for a diagnosis.

Diagnosis of Hashimoto’s disease

In general, your doctor may test for Hashimoto’s disease if you’re feeling increasingly tired or sluggish, have dry skin, constipation, and a hoarse voice, or have had previous thyroid problems or a goiter.

Diagnosis of Hashimoto’s disease is based on your signs and symptoms and the results of blood test. These may include:

Thyroid function test: This blood test tells whether your body has the right amounts of thyroid stimulating hormone (TSH) and thyroid hormone. A high level of TSH is a sign of an underactive thyroid. When the thyroid begins to fail, the pituitary gland makes more TSH to trigger the thyroid to make more thyroid hormone. When the damaged thyroid can no longer keep up, your thyroid hormone levels drop below normal.

An antibodies test: This test confirm the presence of antibodies against thyroid peroxidase (TPO antibodies). The presence of TPO antibodies in your blood suggests that, the cause of thyroid disease is an autoimmune disorder. Furthermore, TPO antibody test isn’t always positive in everyone with Hashimoto’s thyroiditis. However, many people have TPO antibodies present, but don’t have a goiter, hypothyroidism or other problems.


Most patients with Hashimoto’s thyroiditis will require lifelong treatment with levothyroxine. Furthermore, synthetic levothyroxine taken orally at an appropriate dose, is an inexpensive and very effective in restoring normal thyroid hormone levels. It results in an improvement of symptoms of hypothyroidism.

In addition, Regular use of levothyroxine can return your thyroid hormone levels to normal. However, you’ll probably need regular tests to monitor your hormone levels. This allows your doctor to adjust your dose as necessary.


Left untreated, an underactive thyroid gland (hypothyroidism) caused by Hashimoto’s disease can lead to a number of health problems:

  • Goiter
  • depression
  • Heart problems
  • Mental health issues
  • Myxedema
  • Birth defects

Hashimoto’s can also cause problems during pregnancy. Furthermore, babies born to women with untreated hypothyroidism due to Hashimoto’s disease may have a higher risk of birth defects than do babies born to healthy mothers. Doctors have long known that these children are more prone to intellectual and developmental problems. There may be a link between hypothyroid pregnancies and birth defects, such as a cleft palate.

A connection also exists between hypothyroid pregnancies and heart, brain and kidney problems in infants. If you’re planning to get pregnant or if you’re in early pregnancy, be sure to have your thyroid level checked.

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Enlarged Thyroid (Goiter)

A Goiter is an abnormal enlargement of thyroid gland which is a butterfly-shaped organ located at the base of your neck. It indicates a condition, in which, thyroid grows abnormally. Goiter commonly develops as a result of iodine deficiency or due to thyroid problem.

In other words, if your thyroid gland is producing too much hormones ie. (hyperthyroidism) or too little (hypothyroidism), you can develop a goiter. Women are more likely to develop a goiter than men.

Further, it is important to know that, having a goiter doesn’t always mean that your thyroid gland is malfunctioning. However, an enlarged thyroid gland can produce a normal amount of hormones. Goiters are generally pain less but some times you may feel difficulty in swallowing food and breathing.


Very primary symptom of goiter is a noticeable swelling in front of the neck. Not all the goiter cause symptoms but in some cases people experience symptoms given below:

  • Tightness in throat
  • Difficulty in swallowing
  • Lump in neck
  • Coughing
  • Voice hoarseness
  • In severe cases, difficulty breathing

What causes goiter?

There are different conditions that causes Goiter.

Iodine Deficiency: The primary activity of the thyroid gland is to concentrate iodine from the blood to make thyroid hormone. The gland cannot make enough thyroid hormone if it does not have enough iodine.

Therefore, due to iodine deficiency the individual will become hypothyroid. Consequently, the pituitary gland in the brain senses the thyroid hormone level is too low and sends a signal Thyroid Stimulating Hormone (TSH) to the thyroid. This hormone (TSH) stimulates the thyroid to produce more thyroid hormone and to grow in size. Hence, this abnormal growth in size of thyroid is termed a “goiter.”

Hashimoto’s disease : The main cause of goiter in developed countries is autoimmune disease. Hashimoto’s disease is an autoimmune disorder. It damages your thyroid, causing low production of hormones ie. (Hypothyroidism).

As a result, sensing a low hormone level, your pituitary gland produces more Thyroid Stimulating Hormone (TSH) . This hormone stimulates the thyroid to produce more thyroid hormone and to grow in size. This abnormal growth in size of thyroid is termed a “goiter.”

Hormonal Changes: Women leading to menopause can develop a goiter as there are so many hormonal changes occurs at that time. Women above age of 40 have more chances to develop it. Pregnancy also makes so many hormonal changes in women, so this can also lead to develop a goiter.

Family History: Hereditary factors may cause goiter. If one of the parent is suffering from it, then you may have chances to develop it as well.

How is goiter diagnosed?

  • Physical Examination: Your doctor may be able to tell if the thyroid gland has grown by feeling the neck area for nodules and signs of tenderness.
  • Ultrasound of the thyroid: It is a procedure which sends high frequency sound waves through thyroid to find out the gland’s size and nodules. It can be used to visualize the thyroid gland.
  • Hormone test: A blood test which measures the hormone levels of the body to check the proper working of thyroid.
  • CT scan: CT scan or MRI is used to measure the size of goiter.
  • Biopsy: In this procedure a small specimen is taken from thyroid tissue with a needle and send it to laboratory for further examination.


Your doctor will decide on a course of treatment based on the size and condition of your goiter, and symptoms associated with it.

  • Medications: If you have hypothyroidism, then thyroid hormone replacement with levothyroxine will resolve the symptoms of it. This also slow down the release of thyroid stimulating hormone from your pituitary gland, often decreasing the size of the goiter.
  • Radioactive iodine treatment: This treatment is used in cases of an overactive thyroid gland. It involves taking radioactive iodine orally. Furthermore, iodine goes to thyroid gland through your bloodstream and kills thyroid cells. The treatment results in a diminished size of the goiter. However, After this treatment, the patient usually has to take thyroid hormone replacement therapy for the rest of his or her life.
  • Surgery: It is performed to remove all or part of your thyroid gland. It may also be needed if the goiter is large and causes problems with breathing and swallowing. Surgery is also sometimes used to remove nodules. It must be done if cancer is present. You may also need to take levothyroxine after surgery, depending on the amount of thyroid removed.

Diet and Yoga

Diet: If your goiter is caused by your diet then you may need to increase or decrease your iodine intake at home.

Kindly discuss your diet plan with your doctor. He/She will tell you how much iodine is required per day for keeping your thyroid healthy.

Yoga: Yoga brings many benefits to your overall health. It can help treat your thyroid gland naturally. Several studies have shown the positive effect of yoga for improving thyroid function.

However, it is important to know that Yoga can not cure but can help maintain and improve your thyroid function. Kindly note, Yoga is a complementary therapy and should not be used as a replacement for your existing medical treatment. Therefore, before you start practicing yoga for thyroid problems, make sure to consult with your doctor. 

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