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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Antithyroid Medications

Antithyroid medications are used to treat an overactive thyroid gland (also know as hyperthyroidism). When the thyroid gland is overactive, it makes too much thyroxine (also known as T4). The extra thyroxine can accelerate the metabolism rate of your body. As a result, it can cause weight loss and irregular heart activity.

Antithyroid Medication Image

Therefore, antithyroid medications (which includes methimazole and propylithiouracil) are used to reduce the amount of hormone (T4) released by the thyroid gland. These drugs does not affect the thyroxine which is already made, but reduce the further production. Therefore, it may take four to eight weeks of treatment for your thyroxine level to come down to normal.

Antithyroid Drugs during pregnancy

If you take antithyroid drugs, you should discuss your treatment with your doctor before becoming pregnant:

  • Methimazole: Using methimazole during pregnancy could harm the unborn baby. Tell your doctor if you are pregnant or if you become pregnant while using this medicine.

Methimazole can pass into breast milk and may harm a nursing baby. Ask your doctor about any risk.

  • Propylthiouracil: Do not use propylthiouracil if you are pregnant. Tell your doctor right away, if you become pregnant. This medicine can harm an unborn baby, or cause serious liver problems or death of the baby or the mother. You may need to use another medication during late pregnancy.

It may not be safe to breast-feed while using propylthiouracil. Ask your doctor about any risk.

Side Effects of Antithyroid medications?

You may require careful monitoring to get the right levels of these medicines for you. However, when taking an antithyroid medicine, if you develop any of the side-effects (listed below) or any other signs of infection, you must stop the medicine and report this to your doctor immediately.

  • Rash
  • Mild stomach upset
  • Headache
  • Painful joints

The above side-effects are usually not serious and often go, even if you continue with the medication.

But in rare cases, antithyroid medicine can cause a serious side-effect on the blood-making cells. This can drastically reduce the number of blood cells in your body, including the cells that fight off infection and those that help to stop bleeding.

There’s also the risk of liver damage. Therefore, see your doctor right away if you develop following symptoms, while taking these drugs.

  • A sore throat.
  • Mouth ulcers.
  • Unexplained bruising or bleeding.
  • Rash
  • Fever
  • Itching
  • Jaundice (yellowing of the skin and eyes)
  • Any other signs of infection.
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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 TSH ?

TSH stands for thyroid stimulating hormone. It is produced and released into the bloodstream by the pituitary gland (a pea-sized structure), which is located at the base of your brain. It is responsible for regulating many hormones released by the thyroid gland.

Furthermore, your thyroid gland controls different bodily functions, including metabolic rate, heart and digestive functions, muscle control, brain development, by releasing a steady amount of thyroid hormones.

Thyroid gland produces two major thyroid hormones:

In addition to the above, the production and release of thyroid hormones are controlled and regulated by thyroid stimulating hormone (TSH), which is secreted by the pituitary gland.

How TSH Levels Change ?

When levels of thyroid hormones decrease below normal, the pituitary gland releases the Thyroid stimulating hormone. This hormone binds to the receptor on the thyroid cells. This causes thyroid cells to produce more hormones (T3 and T4) and release them into the bloodstream. Once the levels of thyroid hormones rise, the pituitary gland then decreases TSH production.

In this way, the two glands work together to make sure the right amount of thyroid hormones are produced.

  1. First, your pituitary gland senses the level of thyroid hormone that is released into the bloodstream by your thyroid gland.

  2. When your thyroid gland, due to illness, stress, surgery, obstruction, or due to whatever reason, doesn’t produce enough thyroid hormone, your pituitary gland detects the reduced levels of thyroid hormones and moves into action by making more TSH, which then triggers your thyroid to make more thyroid hormones (T3 and T4).

    This is the pituitary’s effort to raise the levels of thyroid hormone and return the system to normal.

  3. If your thyroid is overactive and producing too much thyroid hormone, due to disease or taking too high a dose of thyroid hormone replacement drugs, your pituitary gland senses that there is too much of the hormone circulating and slows or shuts down TSH production.

    This drop in TSH is an attempt to return circulating thyroid hormones levels to normal.

Why do I need a TSH test?

A TSH test can be used to check how well your thyroid gland is functioning. It measures the amount of thyroid stimulating hormone that your pituitary gland is secreting. Your doctor may order a TSH test, if you’re experiencing symptoms of a thyroid disorder.

TSH Test

Thyroid diseases can be categorized as either hypothyroidism (too little thyroid hormone) or hyperthyroidism (too much thyroid hormone)

Symptoms of hypothyroidism, also known as underactive thyroid, include:

  • Hair Loss
  • Puffy Face
  • Dry Skin
  • Slow Heartbeat
  • Constipation
  • Irregular Periods in women
  • Loss of interest in sex
  • Cold Sensitivity
  • Tiredness
  • Sore Muscles
  • Joint Pain
  • Depression
  • Weight Gain
Hypothyroidism Symptoms Image

Symptoms of hyperthyroidism, also known as overactive thyroid, include:

  • Bulging Eyes
  • Abnormal Heart Rate
  • Diarrhea
  • Weight Loss
  • Irritability
  • Itching
  • Heat Intolerance
  • Stress
  • Sleeplessness
  • Vision Problem
  • Frequent Sweating
  • Irregular Mensuration
  • Nervousness
Hyperthyroidism Symptoms Image

TSH tests are also used to screen newborn babies for underactive thyroid, and to diagnose fertility problems in women.

This test is frequently ordered along with or prior to a free T4 test. Other thyroid tests that may be ordered include total or free T3 tests. TSH, free T4 and sometimes free T3 may be ordered together as a thyroid panel.

What does the TSH test result means ?

High TSH levels can mean your thyroid is not making enough thyroid hormones, a condition called hypothyroidism. Low TSH levels can mean your thyroid is making too much of the hormones, a condition called hyperthyroidism.

Please note, a TSH test does not explain why TSH levels are too high or too low. If your test results are abnormal, your health care provider will probably order additional tests to determine the cause of your thyroid problem. These tests may include:

  • T4 thyroid hormone tests
  • T3 thyroid hormone tests
  • 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 TSH test?

It’s important to tell your doctor about all of the medications you’re currently taking. Many multivitamins, supplements, and prescription medications may interfere with the accuracy of the TSH test results. Therefore, their use should be discussed with your doctor, prior to testing.

You may need to avoid using these drugs before the test. However, don’t stop taking your medications unless your doctor tells you to do so.

In addition to the above, you may also need to fast (not eat or drink) for several hours before the test. Remember, TSH levels can vary throughout the day, so it’s best to have this test done early in the morning. Your health care provider will let you know if there are any special instructions to follow.

How is a TSH Test Performed?

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). You may feel a little sting when the needle goes in or out.

Blood sample from a vein Image
Blood sample from a vein

The entire procedure should only take a few minutes to complete. The blood sample will be sent to a lab for analysis. Once your doctor receives the test results, they’ll schedule an appointment with you to discuss the results and explain what they may mean.

TSH Test Reference range

TSH Test reference range are only one indicator of how your thyroid is functioning. They vary by gender, age, and other factors. In general, normal, low, and high TSH levels are:

AgeReference Range
( μIU/mL)
( μIU/mL)
( μIU/mL)
0-5 Days0.70 – 15.20<0.70>15.20
6 Days – 2 Months0.70 – 11.00<0.70>11.00
3 Days – 11 Months0.70 – 8.40<0.70>8.40
1 – 5 Years0.70 – 7.00<0.70>7.00
6 – 10 Years0.60 – 4.80<0.60>4.80
11 – 15 Years0.50 – 4.70<0.50>4.70
> 20 Years (Adults) 0.27 – 4.70<0.27>4.70

Dear reader, I have also attached my Thyroid Function Test Report for your reference. (Click Here to see report)

TSH levels in women

Women are at greater risk for developing abnormal TSH levels during menstruation, when giving birth, and after going through menopause.

Furthermore, a 2017 study showed that older women are especially at risk for developing thyroid cancer if they have high TSH levels along with thyroid nodules.

TSH levels in men

Both high and low TSH can affect fertility. Men with hypothyroidism or hyperthyroidism both had fewer normally shaped sperm.

In addition, men are more susceptible than women to complications like irregular development of the genitals if they have high TSH. Taking thyroid hormone replacement therapy may be necessary for men to balance TSH.

TSH levels in children

TSH levels in children can vary based on their age. A 2008 study that closely measured TSH levels in kids from birth to as old as 18 years found wildly different TSH levels throughout their lives.

And though TSH tends to be high for the first month after they’re born, a child’s TSH levels will gradually decrease as they get closer to adulthood before rising again as they age.

TSH levels in pregnancy

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 for pregnant women.

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

When TSH Test alone is Not Enough ?

During diagnosis, most doctors use the thyroid stimulating hormone test to evaluate thyroid function and determine the optimal course of treatment. There are times, however, when a TSH may be insufficient.

For example, free T4 test in addition to TSH is usually ordered, if a doctor suspects thyroid dysfunction arising from disease of the pituitary gland or hypothalamus. Likewise, if the TSH is normal, but a person still has symptoms of being hyperthyroid or hypothyroid, free T4 test may be ordered.

TSH is also not necessarily sufficient to monitor hypothyroidism during pregnancy, therefore, a T4 and free T4 tests are often recommended. Depending on the clinical situation, other thyroid tests that may be ordered include triiodothyronine (T3), free T3 and thyroid antibody tests.


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

Normal TSH reference range can vary widely, depending on a person’s age, gender, and other factors. A reference range can also vary between different laboratories, however, for most adults (>20 Years), the normal range falls between 0.27 and 4.70 μIU/mL.

Furthermore, make sure you get your TSH levels tested regularly, especially if you have a family history of thyroid disorders or have seen abnormal TSH levels on previous test results.

Follow all the instructions your doctor gives you to stop taking certain medications or eating certain foods before a TSH test to make sure the results are accurate. This way, your doctor can give you a treatment plan that’s best for the cause of abnormal TSH.

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