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Thyroid function tests (TFTs) is a collective term for blood tests used to check the function of the thyroid. [1] TFTs may be requested if a patient is thought to suffer from hyperthyroidism (overactive thyroid) or hypothyroidism (underactive thyroid), or to monitor the effectiveness of either thyroid-suppression or hormone replacement therapy.
The patient swallows a radioisotope of iodine in the form of capsule or fluid, and the absorption (uptake) of this radiotracer by the thyroid is studied after 4–6 hours and after 24 hours with the aid of a scintillation counter. The dose is typically 0.15–0.37 MBq (4–10 μCi) of 131 I iodide, or 3.7–7.4 MBq (100–200 μCi) of 123 I ...
Jostel's TSH index (TSHI or JTI), also referred to as Jostel's thyrotropin index or Thyroid Function index (TFI), is a method for estimating the thyrotropic (i.e. thyroid stimulating) function of the anterior pituitary lobe in a quantitative way. [1] [2] The equation has been derived from the logarithmic standard model of thyroid homeostasis.
People with hyperthyroid will typically "take up" higher than normal levels of radioiodine. Normal ranges for RAI uptake are from 10 to 30%. In addition to testing the TSH levels, many doctors test for T 3, Free T 3, T 4, and/or Free T 4 for more detailed results. Free T 4 is unbound to any protein in the blood.
The gland increases in size by 10%, thyroxine production increases by 50%, and iodine requirements increase. Many women have normal thyroid function but have immunological evidence of thyroid autoimmunity (as evidenced by autoantibodies) or are iodine deficient, and develop evidence of hypothyroidism before or after giving birth. [44]
The TRH test involves administration of a small amount of TRH intravenously, [1] following which levels of TSH will be measured at several subsequent time points using samples of blood taken from a peripheral vein. [citation needed] The test is used in the differential diagnosis of secondary and tertiary hypothyroidism.
The elevation is usually a marked increase over the normal range. [13] TSH is the preferred initial test of thyroid function as it has a higher sensitivity to changes in thyroid status than free T 4. [62] Biotin can cause this test to read "falsely low". [21]
Thyroid disease is a medical condition that affects the function of the thyroid gland. The thyroid gland is located at the front of the neck and produces thyroid hormones [ 1 ] that travel through the blood to help regulate many other organs, meaning that it is an endocrine organ .