Editing Thyroid (section)

===Tests===
[[Thyroid function test]]s include a battery of [[blood test]]s, including the measurement of the thyroid hormones, as well as the measurement of thyroid stimulating hormone (TSH).{{sfn|Greenspan's|2011|p=184}} They may reveal hyperthyroidism (high T<sub>3</sub> and T<sub>4</sub>), hypothyroidism (low T<sub>3</sub>, T<sub>4</sub>), or subclinical hyperthyroidism (normal T<sub>3</sub> and T<sub>4</sub> with a low TSH).{{sfn|Greenspan's|2011|p=184}}

TSH levels are considered the most sensitive marker of thyroid dysfunction.{{sfn|Greenspan's|2011|p=184}} They are however not always accurate, particularly if the cause of hypothyroidism is thought to be related to insufficient [[thyrotropin releasing hormone]] (TRH) secretion, in which case it may be low or falsely normal. In such a case a TRH stimulation test, in which TRH is given and TSH levels are measured at 30 and 60-minutes after, may be conducted.{{sfn|Greenspan's|2011|p=184}}

T<sub>3</sub> and T<sub>4</sub> can be measured directly. However, as the two thyroid hormones travel bound to other molecules, and it is the "free" component that is biologically active, free T<sub>3</sub> and free T<sub>4</sub> levels can be measured.{{sfn|Greenspan's|2011|p=184}} T<sub>3</sub> is preferred, because in hypothyroidism T<sub>3</sub> levels may be normal.{{sfn|Greenspan's|2011|p=184}} The ratio of bound to unbound thyroid hormones is known as the thyroid hormone binding ratio (THBR).{{sfn|Harrison's|2011|p=2229}} It is also possible to measure directly the main carriers of the thyroid hormones, thyroglobulin and throxine-binding globulin.{{sfn|Greenspan's|2011|p=186}} Thyroglobulin will also be measurable in a healthy thyroid, and will increase with inflammation, and may also be used to measure the success of thyroid removal or ablation. If successful, thyroglobulin should be undetectable.{{sfn|Harrison's|2011|p=2229}} Lastly, antibodies against components of the thyroid, particularly anti-TPO and anti-thyroglobulin, can be measured. These may be present in normal individuals but are highly [[Psychic|sensitive]] for autoimmune-related disease.{{sfn|Harrison's|2011|p=2229}}

====Imaging====
Ultrasound of the thyroid may be used to reveal whether structures are solid or filled with fluid, helping to differentiate between nodules and goitres and cysts. It may also help differentiate between malignant and benign lesions.{{sfn|Greenspan's|2011|p=189}} 

When further imaging is required, a radiolabelled [[iodine-123]] or [[technetium-99]] uptake scan may take place. This can determine the size and shape of lesions, reveal whether nodules or goitres are metabolically active, and reveal and monitor sites of thyroid disease or cancer deposits [[metastases|outside the thyroid]].{{sfn|Greenspan's|2011|p=188-9}}

A [[fine needle aspiration]] of a sample of thyroid tissue may be taken in order to evaluate a lesion seen on ultrasound which is then sent for [[histopathology]] and [[cytology]].{{sfn|Greenspan's|2011|p=190}}

[[Computed tomography of the thyroid]] plays an important role in the evaluation of thyroid cancer.<ref name=Saeedan2016>{{cite journal | vauthors = Bin Saeedan M, Aljohani IM, Khushaim AO, Bukhari SQ, Elnaas ST | title = Thyroid computed tomography imaging: pictorial review of variable pathologies | journal = Insights into Imaging | volume = 7 | issue = 4 | pages = 601–17 | date = August 2016 | pmid = 27271508 | pmc = 4956631 | doi = 10.1007/s13244-016-0506-5 }} [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License]</ref> CT scans often [[Incidental imaging finding|incidentally find]] thyroid abnormalities, and thereby practically becomes the first investigation modality.<ref name=Saeedan2016/>