Normal Thyroid Levels

Thyroid is a butterfly shaped endocrine gland that produces two types of hormones, T3 and T4. These thyroid hormones are vital for the modulation of metabolic rate in the body. The overall production of T3 and T4 hormones in the body is controlled by the Thyroid Stimulating Hormone (TSH), which is produced by the pituitary gland. TSH, as per the assigned name, activates the thyroid gland to synthesize T3 and T4 hormones. Hence, increased level of TSH is an indication of a malfunctioning thyroid gland. In general, increased TSH level indicates an overactive thyroid gland that overproduces T3 and T4 hormones that is associated with hyperthyroidism. In contrary, an under active thyroid gland reduces the level of these hormones thus, resulting in hypothyroidism. It is advised to learn the normal thyroid levels to determine the thyroid condition. Here’s a detailed outline about the normal reference range of thyroid hormones.

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What is a Normal TSH Level

The normal TSH thyroid level usually depends on the medical lab, clinic, or a consulting physician. Previously, the normal TSH levels ranged from between 0.5 to 5.5.  Currently, the TSH reference scale has been revised to the new standard range and the specified normal TSH level ranges from between 0.3 to 3.3. However, the old reference scale has been still followed by some labs, thus leading to a difference in thyroid treatment. Moreover, the TSH levels generally fluctuate throughout the day especially in the early morning and evening; even though the TSH levels can be same at 6 a.m. and 6 p.m. It has been reported that the TSH reaches it peak level in the evening, continues to be the highest until midnight. In addition, the TSH level considerably drops down at noon and the recorded TSH difference throughout the day varies by 2 – 3 points.

Normal T3 Level

Triiodothyronine (T3) is normally produced in the body at relatively small amounts. However, it is essential for the modulation of basal metabolic rate in the body. In general, the normal T3 thyroid hormone level usually differs from the type of test that has been performed. However, the normal reference range of Total T3 is recommended to be between 80 to 220 points. The highest thyroid level ranging above 220 points is a sign of hyperthyroidism or overactive thyroid; while the level below 80 indicates hypothyroidism or underactive thyroid. Another preferred test includes Free T3 which indicates normal thyroid levels when ranges from 2.3 to 4.2. Thyroid levels that are below the lower and above the upper limit indicate an abnormal activity of the thyroid gland.

Normal T4 Level

Thyroxine (T4) hormone is generally circulated in the blood through proteins. The liver converts T4 to T3 hormone. Two types of tests are suggested to determine the T4 level in blood. The normal total T4 range that indicates normal thyroid function ranges from between 4.5 to 12.5. The normal Free T4 levels can range from between 0.7 to 2. If the thyroid levels are above or below this preferred normal range, then it is more likely to be either one of these conditions; hypothyroidism or hyperthyroidism.

Below is the recommended normal range of thyroid hormones:

  • The normal TSH reference level ranges from between 0.3 to 3.0

  • The normal total T3 level ranges from 80 to 220 points.

  • The normal Free T3 level can vary from between 2.3 to 4.2.

  • The normal reference range forTotal T4 can vary from 4.5 to 12.5.

  • The normal range of Free T4 can vary from between 0.7 to 2.0.

Interpretation of Thyroid Test Results

Here is helpful information that can help to determine the signification of the above mentioned thyroid tests

First of all, it is important to learn the normal preferred range of a thyroid test by your doctor’s office.

  • The commonly preferred range of Thyroid Stimulating Hormone (TSH) at most labs can be from 0.5 to 5.5; however, some experts follow the recently updated reference range of 0.3 to 3.0.

  • If the TSH level is less than 0.3, the condition can be diagnosed as an overactive thyroid or hyperthyroid.

  • If the TSH level is above 3, then the condition is referred to underactive thyroid or hypothyroid.

  • The normal range for total T4 or Total Thyroxine is around 4.5 to 12.5.

  • High TSH levels and low total T4 reading are diagnostic of hypothyroidism.

  • Reduced TSH levels and low total T4 reading are suggestive of a pituitary tumor.

  • The normal range for Free T4 or Free Thyroxine test is around 0.7 to 2.0.

  • The free T4 reading below 0.7 is suggestive of hypothyroidism.

  • The normal range of Total T3 test is around 80 to 220

  • Total T3 result below a range of 80 is suggestive of hypothyroidism.

  • The normal Free T3 level ranges between 2.3 to 4.2.

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