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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 TSH, in turn, stimulates the thyroid to produce thyroid hormone until levels in the blood return to normal. Thyroid hormone exerts negative feedback control over the hypothalamus as well as anterior pituitary, thus controlling the release of both TRH from hypothalamus and TSH from anterior pituitary gland. [2] The HPA, HPG, and HPT axes are ...
First, blood is drawn and a baseline TSH level is measured. Then, TRH is administered via a vein. After 30 minutes blood is drawn again and the levels of TSH are measured and compared to the baseline. Some authors recommend additional blood sampling at 15 minutes. In children, late blood sampling at 60 to 120 minutes is necessary.
Serum iron is a medical laboratory test that measures the amount of circulating iron that is bound to transferrin and freely circulate in the blood. Clinicians order this laboratory test when they are concerned about iron deficiency, which can cause anemia and other problems. 65% of the iron in the body is bound up in hemoglobin molecules in red blood cells.
Transferrin saturation (TS), measured as a percentage, is a medical laboratory value. It is the value of serum iron divided by the total iron-binding capacity [1] of the available transferrin, the main protein that binds iron in the blood, this value tells a clinician how much serum iron is bound.
Thyroid disease is a medical condition that affects the structure and/or 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 .
Still, the blood values are approximately equal between the arterial and venous sides for most substances, with the exception of acid–base, blood gases and drugs (used in therapeutic drug monitoring (TDM) assays). [6] Arterial levels for drugs are generally higher than venous levels because of extraction while passing through tissues. [6]
Thyroid's secretory capacity (G T, also referred to as thyroid's incretory capacity, maximum thyroid hormone output, T4 output or, if calculated from serum levels of thyrotropin and thyroxine, as SPINA-GT [a]) is the maximum stimulated amount of thyroxine that the thyroid can produce in a given time-unit (e.g. one second). [2] [3]