THYROID STIMULATING HORMONE (TSH)

Test Interpretation TT3 (Total Triiodothyronine) TT3 measures the total amount of T3 in the blood. Low levels may indicate hypothyroidism, while high levels may indicate hyperthyroidism. TT4 (Total Thyroxine) TT4 measures the total amount of T4 in the blood. Low levels may indicate hypothyroidism, while high levels may indicate hyperthyroidism. TSH (Thyroid Stimulating Hormone) TSH stimulates the thyroid gland to produce thyroid hormones. High levels may indicate hypothyroidism, while low levels may indicate hyperthyroidism.

• Serum T3, T4 and TSH are the measurements form three components of thyroid screening panel and are useful in diagnosing various disorders of thyroid gland function.
•  Primary hyperthyroidism is accompanied by elevated serum T3 and T4 values along with depressed TSH levels.
• Primary hypothyroidism is accompanied by depressed serum T3 and T4 values and elevated serum TSH levels.
• Normal T4 levels accompanied by high T3 levels are seen in patients with T3 thyrotoxicosis. Slightly elevated T3 levels may be found in pregnancy and in estrogen therapy while
• depressed levels may be encountered in severe illness, malnutrition, renal failure and during therapy with drugs like propanolol and propylthiouracil.
• Although elevated TSH levels are nearly always indicative of primary hypothyroidism, rarely they can result from TSH secreting pituitary tumors (secondary hyperthyroidism).
• Low levels of Thyroid hormones (T3, T4 & FT3, FT4) are seen in cases of primary, secondary and tertiary hypothyroidism and sometimes in non-thyroidal illness also.
• Increased levels are found in Grave’s disease, hyperthyroidism and thyroid hormone resistance.
• TSH levels are raised in primary hypothyroidism and are low in hyperthyroidism and secondary hypothyroidism.