- A high TSH level suggests that the thyroid gland is not producing enough thyroid hormone (primary hypothyroidism).
- A low TSH level usually suggest that the thyroid is producing too much thyroid hormone (hyperthyroidism).
- The total thyroxine (T4) hormone measures both bound and free thyroxine levels in the blood.
- Free T4 (FT4) measures the free thyroxine hormone, which is not bound and able to freely enter and affect body tissues.
- Triiodothyronine (T3) levels measures the bound and free fractions of triiodothyronine.
|Type of hormone||Normal levels|
|TSH||0.5 - 5.0 mIU/L|
|T4||80 - 220 ng/dL|
|FT4||0.7 - 1.9 ng/dL|
|T3||5.0 - 12.0 μg/dL|
|Laboratory results||Differential Diagnosis|
|High TSH, low thyroid hormone level||Primary hypothyroidism|
|High TSH, normal thyroid hormone level||Subclinical hypothyroidism|
|Low TSH, high thyroid hormone level||Primary hyperthyroidism|
|Low TSH, normal thyroid hormone level||Early or mild hyperthyroidism|
|Low TSH, high thyroid hormone level|
High TSH, low thyroid hormone level
|Thyroiditis (Thyroid Inflammation)|
|Low TSH, low thyroid hormone level||Pituitary disease|
- Medical Disorders
- Oral Health Care Considerations