What Are the Normal Thyroid Hormone Levels?

If a doctor suspects a thyroid disorder, they may recommend one or more thyroid tests to measure hormone levels in the body and help determine how the thyroid is functioning. So, what are the normal thyroid hormone levels? Keep reading to find out.

Normal Thyroid Hormone Levels: Common Tests

Typically, doctors measure the Thyroid-Stimulating Hormone (TSH) or Thyroxine (T4) levels as initial tests if a thyroid disorder is suspected. Here, we will explain the normal levels of these thyroid hormones:

• Normal TSH Levels

The Thyroid-Stimulating Hormone is produced by the pituitary gland, and its primary function is to stimulate the thyroid gland to produce its hormones. Its levels are often a sensitive indicator of thyroid issues.

Generally, the normal range for TSH levels is between 0.4 - 4.0 milliunits per liter (mU/L), but various factors can affect its level, such as gender, age, pregnancy, and certain diseases. Below are the normal values based on age and gender:

• Normal TSH Levels for Males

TSH levels can increase with age in males as follows:

• Normal TSH Levels for Females

Estrogen levels affect TSH levels, so they differ between males and females, and also vary with age. Here are the normal values:

• Normal TSH Levels for Pregnant Women

During pregnancy, TSH levels vary across trimesters:

• Normal TSH Levels for Children

TSH levels are higher at birth and gradually decrease as the child grows:

• Normal Levels of Free Thyroxine (T4)

Thyroxine (T4) is the primary form of thyroid hormone in the blood and is responsible for metabolism, mood, and body temperature. The thyroid's function is usually assessed by measuring the level of free thyroxine in addition to thyroid-stimulating hormone (TSH), which we discussed in the previous section.

The normal range for free thyroxine (T4) is between 0.8 - 1.8 ng/dL. Its levels can be influenced by various factors, including certain medications, pituitary gland disorders, and a history of thyroid cancer.

As for total thyroxine (T4), which includes both free and protein-bound T4, the normal range is between 5 - 12 µg/dL. Its levels can be affected by factors that influence protein levels in the body, such as liver disease and medications.

Less Common Thyroid Tests and Their Normal Ranges

In some cases, the doctor may order the following tests to diagnose thyroid disorders. Here’s a brief overview of these tests and their normal ranges:

• Triiodothyronine (T3)

This hormone is primarily produced in the thyroid gland, but can also be produced in other tissues by converting thyroxine. The normal range for total triiodothyronine is between 100 - 200 ng/dL, while the normal range for free triiodothyronine is between 3.8 - 4.4 pg/mL.

• Thyroglobulin (Tg)

This is a protein produced by the follicular cells of the thyroid gland. The normal range for healthy individuals is between 3 - 40 ng/mL.

• Thyroid Antibodies

Some thyroid conditions are due to autoimmune disorders, where the body produces antibodies that attack thyroid cells. Here are the normal ranges for thyroid antibodies in adults, with levels above these indicating an autoimmune condition:

• Thyroid peroxidase antibodies (TPOAb): Less than 34 IU/mL.
• Thyroid-stimulating immunoglobulin (TSI): Less than 0.55 IU/L.
• Thyroglobulin antibodies (TgAb): Less than 10 IU/mL.

It's important to note that the normal ranges for thyroid tests can vary slightly between laboratories. Therefore, there's no need to worry. We recommend using Blazma's thyroid test package, where our specialized team will provide a detailed interpretation of your results and the normal ranges to ensure you have a comprehensive understanding of your condition.