Normal Thyroid

What Defines Normal Thyroid Levels

The thyroid gland is a butterfly-shaped gland located at the base of the neck which produces T3 and T4 hormones. The T3 and T4 hormones control the body’s metabolism. Whether you suffer from hyperthyroidism or hypothyroidism depends on the over or under activity of these hormones.
In turn, Thyroid Stimulating Hormone, which is produced by the pituitary gland, signals to the thyroid gland the T3 and T4 hormones to secrete. Therefore, it means that when TSH levels are elevated, the thyroid gland is underactive, and that overactive thyroid is as a result of lowered TSH levels.

Normal Thyroid Levels defined

The UK standard for normal thyroid levels for TSH is on a scale of 0.5 to 5.5. The US mimicked this standard up to 2003, when they redefined their scale to anywhere between 0.3 and 3.3. Like with any change in science, there are still some labs that have opted to stick with the predecessor’s set definition for normal thyroid test levels. This means that treatment for thyroid problems is not consistent. To complicate things, TSH levels are not the same every time you take a test. On average, TSH levels are higher in the evening, say, after 6 p.m., continuing to rise until round about midnight, when they begin to decrease. TSH levels are at the lowest point at midday.

Normal Thyroid Test Levels for T3 and T4 hormones

There is not just one test used to determine T3 and T4 levels.

The “total T3 test” reads normal T3 to be in the range of 80 and 220 points. If thyroid levels drop blow 80, you are said to have underactive thyroid. Test results over 220 points is an indicator of hyperthyroidism, or overactive thyroid. If however, you succumb to the “FreeT3 test, the scale is different. For this one, the normal thyroid level range lies between 2.3 and 4.2. Any reading outside of that denotes thyroid problems.

Let us now look at the normal thyroid test levels for the T4 hormone. Like the T3, there is a choice of two tests: the Total T4 test and the Free T4 test. The normal levels of the former are 4.5 to 12.5. If you take the Free T4 test, a normal result lies between 0.7 and 2.0. Again, whether your doctor diagnoses you with overactive or underactive thyroid is based upon whether you normal thyroid level test result is over or under those parameters.

It is not advisable to make a final diagnosis of thyroid disease based upon TSH levels only. The practitioner has to take into account T3 and T4 levels as well. After all, someone who as thyroid problems can still have normal thyroid levels. In this event, test should be done for antibodies in the blood.

Remember, too that what is the set standard may not be “normal” for each individual case.

external links
wikipedia: normal thyroid levels