Located in the neck, the thyroid gland produces hormones that control metabolism and energy production. These hormones regulate how each cell converts food into calories and utilizes stored fats to create energy. They influence weight control, nerve and gastrointestinal health, nutrient absorption, and energy use. Initiated by thyroid-stimulating hormone (TSH) from the pituitary gland, thyroid hormone production includes two principal types: the active hormone triiodothyronine (T3) and the inactive hormone thyroxine (T4), which is converted to T3. In addition to TSH count, thyroid hormone measurements can include levels of total T3 and T4, and free T3 and T4. Free levels refer to the amount of circulating hormone available for use by your cell, while total levels also include the amount of hormone bound to proteins. Typically, free T3 and T4 readings are considered more reliable indicators of thyroid disturbances than total readings.
| Thyroid Test | Reference Range |
| TSH (Thyroid Stimulating Hormone) | 0.5-4.70 mIU/L |
| Total T4 (Thyroxine) | 4.5-12.5 mIU/L |
| Free T4 (Free Thyroxine) | 0.8-1.8 mIU/L |
| Total T3 (Triiodothyronine) | 80 -200 mIU/L |
| Free T3 (Free Triiodothyronine) | 2.3- 4.2 mIU/L |
