Thyroid stimulating hormone (TSH)
The hypothalamus releases thyrotropin releasing hormone (TRH) which tells the pituitary gland to release TSH. The TSH then causes the thyroid gland to produce Triiodothyronine (T3) and thyroxine (T4). The normal range for TSH should be between 0.5-4.0mIU/L. Lower than 0.5mlU/L would indicate hyperthyroidism and above 4.0mlU/L would indicate hypothyroidism. Even values above 2.0mlU/L sometimes indicates hypothyroidism.
Free T3 (FT3) has a normal range of 10-20pmol/L with those below 10pmol/L indicating hypothyroidism and those above 20pmol/L indicating hyperthyroidism.
Free t4 (FT4) has a normal range of 3.5 – 6.0pmol/L with those being below 3.5pmol/L indicating hypothyroidism and those above 6.0pmol/L indicating hyperthyroidism.
Thyroid antibody test
As Hashimoto’s thyroiditis is an autoimmune disease, the test used to diagnose this it is a thyroid antibody test, usually thyroid peroxidase antibody (TPO). If the antibody test is negative then there are 3 possible outcomes from this:
- There are no autoantibodies in your blood (you don’t have an autoimmune condition of the thyroid)
- Your autoimmune condition is still developing and can therefore not be detected yet
- Your symptoms are due to another autoimmune disease
If your TPO test is positive, then there are thyroid antibodies detected. The higher the level of TPO’s the more likely that you have an autoimmune thyroid disorder.
Note that these values are just based on the average of a sample of people. You may have low or high values and not have hypothyroidism or hyperthyroidism. You also may be within the range and have hypothyroidism or hyperthyroidism.
References I used