Thyroid gland ( historical background - embryology - anatomy - physiology - evaluation of the thyroid disorders - and thyroiditis

1. THYROID GLAND
Al-Qadisiya Collage Of Medicine
6th Stage

2. THYROID GLAND
Index :-
1- Historical Background
2- Embryology
3- Anatomy
4- physiology
5- Evaluation of Patient with thyroid diseases
6- THYROIDITIS
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Hypo-Hyper-thyroidism &Thyroid neoplasm
Will be discussed in the next week

3. Historical Background
 The term thyroid gland
(Greek thyreoeides,
shield-shaped)
 however, attributed to
Thomas Wharton in his
Adenographia at 1656
In 1776, the thyroid was classified as a ductless gland
by Albrecht von Haller and was thought to have numerous
functions
ranging from lubrication of the larynx to acting as a reservoir
for blood to provide continuous flow to the brain, and to
beautifying women’s necks.

4. Embryology
The thyroid gland arises as
an out pouching of the
primitive
foregut around the third
week of gestation. It
originates at the
base of the tongue at the
foramen cecum.
The developing thyroid lobes arising in the fourth pharyngeal
pouch , while the isthmus arise from Third pharyngeal pouch

5. Embryology
 With further development, the thyroid
descends into the neck anterior to the hyoid
bone and laryngeal cartilages.
 Certain congenital anomalies such as ectopic
thyroid tissue or thyroglossal duct cysts are
directly related to this embryologic descent.
 The parafollicular cells, or C cells, are derived
from the neural crest, migrate to the thyroid,
and produce calcitonin.

6. Embryology
The descent of theThyroid ,
showing possible sites of
ectopic thyroid tissue or
thyroglossal
cysts, and also the course of a
thyroglossal fistula.
The arrow shows
the further descent of the
thyroid that
may take place retrosternally
into the
superior mediastinum.

7. Thyroid Anatomy
The normal thyroid gland weighs
20–25 g. The functioning unit is
the lobule supplied by a single
arteriole and consisting of 24–40
follicles lined with cuboidal
epithelium
Formed of 2 lobes (Rt & Lt), that are connected by band of
tissue called “isthmus”.

8. The blood supply to the thyroid arises from two pairs of main
arteries: the superior thyroid artery (branch of the
external carotid) and the inferior thyroid artery (branch of the
thyro-cervical trunk). A thyroidea ima artery arises directly from
the aorta or innominate in 1% to 4% of individuals to enter the
isthmus
Venous return :-
The superior thyroid
veins & The middle vein .
The superior and middle
veins drain directly into
the internal jugular veins.
The inferior veins often
form a plexus, which
drains into the
brachiocephalic veins

9. The recurrent laryngeal nerve (RLN)
usually courses 1 cm anterior or
posterior to the inferior thyroid artery.
Careful dissection around this artery is
necessary to avoid injury to the RLN.
Lymphatic Drainage
1- direct to deep cervical L.N
2- sub capsular plexuses :-
A- juxtathyroid node ( Delphian )
centrally located
B- pretracheal L.N
C- L.N along the veins
3- The drain to deep cervical and
mediastainal L.N

10. Thyroid physiology
The thyroid gland is concerned with the synthesis of the iodine
- containing hormones thyroxine (tetra - iodothyronine, T4)
and tri – iodothyronine (T3) , which control the metabolic rate
of the body;
T3 is the active hormone, and T4 is converted to
T3 in the periphery.
The thyroid gland also secretes calcitonin from the
parafollicular C cells, which reduces the level of serum calcium
and is therefore antagonistic to parathormone.

11. Physiological control of secretion
The immediate control of synthesis and
liberation of T3 and T4 is by
thyroid - stimulating hormone
(TSH) produced by the anterior pituitary.
TSH is secreted in response to the level of
thyroid hormones in the blood by
a negative feedback mechanism.
The secretion of TSH is also under
The influence of the
hypothalamic -thyrotrophin -
releasing hormone ( TRH )

12. Evaluation of thyroid disorders
1- History ( discuss in each topic )
2- examination
3- Biochemical tests
4- Radiological tests
5- FNAC
6- Core Biopsy
7- laryngoscope

13. Biochemical Evaluation of thyroid disorders
1- Measurement of TSH (0.3 to 5 mIU/L) is the most useful
biochemical test in the diagnosis of thyroid illness. In most
patients without pituitary disease, increased TSH signifies
hypothyroidism, suppressed TSH suggests hyperthyroidism,
and normal TSH reflects a euthyroid state
2- Assessment of free T 4 (4.5 to 11.2 μg/dL) concentration
supports identified abnormalities in TSH and provides an index
of severity of illness .

14. Biochemical Evaluation of thyroid disorders
3- Measurement of T 3 (80 to 200 ng/dL) is unreliable as a test
for hypothyroidism. This test is useful in the occasional patient
with suspected hyperthyroidism, suppressed TSH, and normal
T4 (T3 thyrotoxicosis).
4- Anti-thyroid antibodies are found in the serum of patients
with autoimmune thyroiditis (Hashimoto thyroiditis).
5- Anti-TSH receptor antibodies, which stimulate the TSH
receptor, are detectable in more than 90% of patients with
autoimmune hyperthyroidism (Graves' disease).

15. Biochemical Evaluation of thyroid disorders

16. Radiological Evaluation of thyroid disorders
1- Chest X-ray 2- Ultrasound 3- CT & MRI 4- Isotope scan
5- PET scan
Chest and thoracic inlet radiograph
Simple radiographs of the chest and thoracic inlet will rapidly
and economically confirm the presence of significant
retrosternal goitre and clinically important degrees of tracheal
deviation and compression. Pulmonary metastases may also
be detected

18. Radiological Evaluation of thyroid disorders
1- Chest X-ray 2- Ultrasound 3- CT & MRI 4- Isotope scan
5- PET scan
Ultrasound scanning
High-frequency ultrasound scanning gives good anatomical
images of the thyroid and surrounding structures but,
unfortunately , reveals more thyroid swellings than are
clinically relevant. After a period of years the ultrasound is
enjoying a revival as a means of reducing the number of
unsatisfactory aspiration cytology samples; it permits more
targeted sampling, allowing the identification of parathyroid
adenomas and nodes involved in thyroid cancer.

19. Transverse scan of normal thyroid.
R, right lobe; L, left lobe; T, trachea

20. Radiological Evaluation of thyroid disorders
1- Chest X-ray 2- Ultrasound 3- CT & MRI 4- Isotope scan
5- PET scan
Computerised tomography & magnetic resonance imaging
These are not indicated for thyroid swellings and are reserved
for the assessment of known malignancy and to assess the
extent of retro-sternal and, occasionally, recurrent goitres. The
appearance of a retro-sternal goitre on CT can give a
misleading impression of the operative difficulty in delivery
through a neck incision

21. Computerised tomography scan of the chest showing a retrosternal
goitre with tracheal displacement (arrowed)

22. Sagital CT section showing goitre filling posterior
mediastinum.

23. Radiological Evaluation of thyroid disorders
1- Chest X-ray 2- Ultrasound 3- CT & MRI 4- Isotope scan
5- PET scan
Isotope scanning
The uptake by the thyroid of a low dose of either radiolabelled
iodine (123I) or the cheaper technetium (99mTc) will demonstrate
the distribution of activity in the whole gland. Routine isotope
scanning is unnecessary and inappropriate for distinguishing
benign from malignant lesions because the majority (80%) of ‘cold’
swellings are benign and some (5%) functioning or ‘warm’ swellings
will be malignant. Its principal value is in the toxic patient with a
nodule or nodularity of the thyroid. Localisation of overactivity in
the gland will differentiate between a toxic nodule with suppression
of the remainder of the gland and toxic multinodular goitre

24. Technetium thyroid scan showing a ‘cold’ nodule that
does not take up isotope expanding the left thyroid lobe

25. Technetium thyroid scan showing appearance of a 1-cm

26. Radiological Evaluation of thyroid disorders
1- Chest X-ray 2- Ultrasound 3- CT & MRI 4- Isotope scan
5- PET scan
PET scan may be useful, particularly in localising disease which
does not take up radioiodine.

27. Fine-needle aspiration cytology (FNAC)
is the investigation of choice for
discrete thyroid swellings. FNAC has
excellent patient compliance, is simple
and quick to perform in the out-patient
department and is readily
repeated. FNAC results should be
reported using standard terminology.
There is a trend to use ultrasound to
guide the needle to achieve more
accurate sampling and reduce the rate
of unsatisfactory aspirates

28. Fine-needle aspiration cytology (FNAC)
Classification of fine-needle aspiration cytology
reports
Thy1 = Non-diagnostic
Thy2 = Non-neoplastic
Thy3 = Follicular
Thy4 = Suspicious of cancer
Thy5 = Malignant

29. Core biopsy
Core biopsy gives a strip of tissue for histological rather than
cytological assessment. It has a high diagnostic accuracy but
requires local anaesthesia, and may be associated with
complications
such as :- pain, bleeding, tracheal and recurrent laryngeal
nerve damage.

30. Laryngoscope
Flexible laryngosopy is widely used preoperatively to
determine the mobility of the vocal cords, although usually for
medicolegal rather than clinical reasons.
Nevertheless, the presence of a unilateral cord palsy coexisting
with a swelling suggestive of malignancy is usually diagnostic.

31. Laryngoscope

32. THYROIDITIS
Thyroiditis is a group of autoimmune and
inflammatory disorders characterized by
infiltration of the thyroid with inflammatory cells and
subsequent fibrosis of the gland..

33. THYROIDITIS
Autoimmune thyroiditis
is a chronic autoimmune disorder characterized by destructive
lymphocytic infiltration of the thyroid.
The disease is 15 times more common in women, and more
than 90% of patients have circulating antibodies directed
against
thyroid microsomes and thyroglobulin.

34. THYROIDITIS
Autoimmune thyroiditis
Although patients initially are euthyroid,
hyperthyroidism and hypothyroidism may occur later.
Thyroid hormone is given to hypothyroid patients both as
replacement therapy and to suppress TSH.
Thyroidectomy is indicated for :-
1- compressive symptoms,
2- a dominant nodule
3- suspicious for malignancy,
4- or cosmetic preference.

35. THYROIDITIS
Acute suppurative thyroiditis
is rare and caused by pyogenic infection with
Streptococcus or Staphylococcus species. Treatment
consists of appropriate antibiotic therapy and surgical
drainage of abscesses. Long-term effects on thyroid
function are uncommon.

36. THYROIDITIS
Subacute (de Quervain) thyroiditis
is a rare condition that occurs in young women,
often after a viral upper respiratory tract infection.
Symptoms include fatigue, weakness, and painful
thyroid enlargement radiating to
the patient's jaw or ear

37. THYROIDITIS
Subacute (de Quervain) thyroiditis
Fine needle aspiration (FNA) can be diagnostic with
the identification of giant cells.
Treatment with non steroidal anti-inflammatory drugs
or steroids can alleviate symptoms.
The condition almost always remits spontaneously
within a few weeks.

38. THYROIDITIS
Riedel's thyroiditis
is a rare, progressive inflammatory condition of the
entire thyroid gland, strap muscles, and other neck
structures. Its cause is unknown, and it can be
associated with other fibrotic processes, including
retroperitoneal fibrosis, sclerosing cholangitis, and
fibrosing mediastinitis

39. THYROIDITIS
Riedel's thyroiditis
Riedel's thyroiditis may require surgical excision to
exclude malignancy or relieve compressive symptoms
on the trachea or esophagus.