4. Thyroid Gland
The thyroid, or thyroid gland, is an endocrine gland in
vertebrates. In humans it is in the neck and consists of
two connected lobes. The lower two thirds of the lobes
are connected by a thin band of tissue called the thyroid
isthmus. The thyroid is located at the front of the neck,
below the Adam's apple.
The thyroid gland secretes three hormones: the two
thyroid hormones – triodothyronine (T3) and thyroxine
(T4) – and a peptide hormone, calcitonin.
5. thyroid gland
STRUCTURE :The thyroid gland anatomy comprises a butterfly-shaped organ
which has two lobes that are connected with the help of a narrow isthmus.
The gland weighs 25g in adults, and the lobe is 5cm long and has a thickness
of 2cm. The gland is smaller in men as compared to women. The gland lies in
front of the trachea and larynx in the anterior of the neck. The thyroid gland
diagram is given below.
LOCATION :The specific thyroid gland location is that it is located in the front
part of the neck in the middle of C5 and T1 vertebrae. The thyroid gland's
anatomy has two lobes which are embedded in the posterior surfaces of the
parathyroid gland. This is the thyroid gland location.
FUNCTION :Primarily thyroid gland's function is the secretion of hormones
that affect all the body tissues. Hence in anatomy thyroid gland plays a crucial
role. The hormones secreted by the thyroid gland include the
Triiodothyronine (T3) hormone and the Thyroxine hormone (T4). These
thyroid gland hormones perform different essential tasks in the body.
Thyroxine is released into the bloodstream by the thyroid gland and travels to
organs like the kidney and liver where they are transformed into its active
state triiodothyronine..
6. Blood SUPPLY AND INNERVATION of thyroid gland
Arterial Supply
• Superior thyroid artery – arises as the first branch of the external
carotid artery. It lies in close proximity to the external branch of the
superior laryngeal nerve (innervates the larynx).
• Inferior thyroid artery – arises from the thyrocervical trunk (a branch
of the subclavian artery). It lies in close proximity to the recurrent
laryngeal nerve (innervates the larynx).
INNERVATION :
The thyroid receives innervation from both the sympathetic and
parasympathetic nervous systems, which are subsets of the autonomic
nervous system.
Sympathetic input is supplied by the superior cervical ganglion and the
cervicothoracic ganglion. The superior cervical ganglion lies posterior
to the sheath of the internal carotid artery and internal jugular vein.
The parasympathetic input is supplied by the superior laryngeal nerve
and the recurrent laryngeal nerve.
7.
8. THYROID IMAGING
THYROID SCANS CAN HELP YOUR DOCTOR DETERMINE IF YOUR
THYROID IS WORKING PROPERLY. YOU MAY ALSO HAVE
A RADIOACTIVE IODINE UPTAKE (RAIU) TEST WITH THE SCAN TO
MEASURE YOUR THYROID’S REACTION.
A THYROID SCAN CAN BE USED TO EVALUATE ABNORMALITIES
FOUND IN A PHYSICAL EXAM OR LABORATORY TEST. THE IMAGES
FROM THIS TEST CAN BE USED TO DIAGNOSE:
•LYMPS, NODULES (CYSTS), OR OTHER GROWTHS
•INFLAMMATION OR SWELLING
•AN OVERACTIVE THYROID, OR HYPERTHYROIDISM
•AN UNDERACTIVE THYROID, OR HYPOTHYROIDISM
9. THYROID SCAN PROCEDURE :
-Thyroid scans are usually performed on an outpatient basis in the
nuclear medicine department of a hospital. They can be administered
by a nuclear medicine technologist. Your endocrinologist may or may
not be there during the procedure.
-Before any thyroid scan, you’ll receive radionuclide in the form of a
pill, liquid, or injection. When you’ve waited the necessary amount of
time for the radioactive iodine to be absorbed, you’ll return to the
nuclear medicine department.
Thyroid scan procedure
-You’ll lie down on an examination table for a thyroid scan without
RAIU Radioactive Iodine Uptake. The technologist will tip your head back so
that your neck is extended. They’ll then use a scanner or camera to
take photos of your thyroid, usually from at least three different
angles. You’ll be asked to stay very still while the images are taken. The
process takes about 30 minutes.
10. RAIU procedure
An RAIU is performed 6 to 24 hours
after taking the radionuclide. You’ll
sit upright in a chair for this test.
The technologist will place a probe
over your thyroid gland, where it
will measure the radioactivity
present. This test takes several
minutes.
You’ll return to the nuclear
medicine department to have
another set of readings taken 24
hours after the first test. This
allows your doctor to determine
the amount of thyroid hormone
produced between the two tests.
11. THYROID GLAND :CT SCAN
Ordinary X-ray testing does not show clear images of soft tissue,
so doctors often request CT thyroid scanning to get a good image
of soft tissue including organs, muscles, blood vessels and
nerves.
A CT scan of the thyroid may be completed in order to assist a
doctor during tissue removal, fluid removal or as a guide during
surgery.
When a CT of the thyroid is taken, the spine, airway, carotid
vessels and other vasculature as well as salivary and thyroid
glands are also included for doctors to view.
The process of taking a CT of the thyroid begins by taking many
different X-ray views at various different angles, which are then
combined with the use of computer processing to create cross-
sectional images of the bones and soft tissue inside of your body.
12.
13. THYROID GLAND :MRI
MRI thyroid is a hardware method of investigation using a
magnetic field used to study this endocrine organ. Scanning
allows you to assess the location and size of the lobes and
isthmus of the gland, their structure, to identify the presence of
inflammatory processes, neoplasms, compression of the gland,
to study adjacent organs and tissues.
14. Goiter
A goiter is an abnormal thyroid gland proliferation that manifests as
multi-nodular, uni-nodular, or non-nodular diffuse glandular
enlargement. A goiter is formed of solid matrix, colloid cysts, blood
products, calcification, and fibrosis, and this heterogeneity may
lead to variable appearances on a CT scan.
US is more sensitive in evaluating thyroid nodules within a goiter;
however, a symptomatic goiter may require surgical treatment with
total thyroidectomy, and in this case CT plays an additional role in
preoperative evaluation. Specific aspects for examination on a CT
scan during the preoperative evaluation for goiter include
extension, mass effect, and suspicious features of malignancy.
15. Conclusion
Thyroid disorders are common and tend to have non-specific
appearances on CT scans. Commonly encountered findings when
evaluating a CT scan of the neck include thyroid nodules, glandular
enlargement, and calcifications.
Management of ITNs depends on several factors including nodule size,
patient's age, overall health status, and the presence or absence of
suspicious features such as lymphadenopathy and/or invasion of
adjacent structures.
A CT scan provides additional important information regarding the
local extension of cancer or presence of mass effect, and is useful in
evaluating recurrent disease. Furthermore, CT examination plays a
crucial role in preoperative evaluation and preoperative surgical
planning for patients with symptomatic goiter.
16. Reference
Originally copied from: Bin Saeedan, Mnahi; Aljohani,
Ibtisam Musallam; Khushaim, Ayman Omar; Bukhari,
Salwa Qasim; Elnaas, Salahudin Tayeb (2016). "Thyroid
computed tomography imaging: pictorial review of variable
pathologies". Insights into Imaging. 7 (4): 601–617.
doi:10.1007/s13244-016-0506-5. ISSN 1869-4101. PMC
4956631. PMID 27271508. Creative Commons Attribution
4.0 International License
