The normal range for T3 is 100 to 200 nanograms per deciliter, and the normal range for T4 is 4.5 to 11.2 micrograms per deciliter, states MedlinePlus. The normal range for TSH is 0.4 to 4.2 microunits per milliliter in adults and 0.7 to 6.4 microunits per milliliter in children, according to WebMD.
High thyroid-stimulating hormone levels may indicate a pituitary gland tumor or hypothyroidism, while low TSH levels may signal hyperthyroidism, pregnancy or pituitary gland damage. The pituitary gland is triggered to release TSH when thyrotropin-releasing hormone is released. TSH then prompts the thyroid to produce triiodothyronine and thyroxine, which are known as T3 and T4 respectively, explains WebMD.
T3 is the thyroid hormone that controls metabolism. High levels of this hormone may indicate hyperthyroidism, liver disease, toxic nodular goiter, pregnancy, the use of estrogen or birth control pills, or T3 thyrotoxicosis. Low levels can suggest hypothyroidism, starvation, thyroiditis, or the presence of a short- or long-term illness, says MedlinePlus.
T4 is the main hormone that the thyroid produces. High T4 levels can indicate trophoblastic disease, high protein levels, germ cell tumors, subacute thyroiditis, graves disease, toxic multinodular goiter or iodine-induced hyperthyroidism. Low levels may suggest malnutrition, illness, hypothyroidism or the use of certain medications, explains MedlinePlus.