• It consist of 2 lobes, each lobe is pear in
shaped measure 2.4-4 cm length 1.5-2 cm in
width 1-1.5 cm in thickness.
• both lobes are connected by isthmus.
•The weight in adult is approximately 10-20
•The isthmus of the thyroid gland is located
midway between apex of thyroid cartilage and
•Located anteriorly in the lower neck,
extending from the level of the fifth cervical
vertebra down to the first thoracic
•Second to fourth tracheal rings
* The thyroid gland is the largest endocrine organ in the
* Highly vascularized; rich blood supply, venous drainage
* The blood flow to the thyroid gland is about 5ml/g/min.
* Its function to secrete sufficient amount of thyroid
Thyroid hormone promote normal growth and development
and regulate energy and heat production.
*The parafollicular cells of thyroid gland secrete calcitonin.
* Primary function of the thyroid gland is the secretion of
- T4 (thyroxine) is primary released hormone
- T3 (triiodothyronine) at least 10 times more active
-T4 is converted to T3 peripherally
* 100% of T4 is synthesized in the thyroid gland.
* Only 25-30% of T3 is synthesized in thyroid gland and
remaining 70-75% are coming from conversion (deiodination)
of T4 into T3 in peripheral tissues.
•Thyroid hormone regulated by thyroid stimulating
hormone (TSH) from the anterior pituitary gland.
•The anterior portion of pituitary gland in turn is
controlled by thyrotropin releasing hormone (TRH)
Effects of thyroid hormone:
*Fetal brain and skeletal maturation.
*Increase in basal metabolic rate.
*Inotropic and chronotropic effects on heart.
*Increases sensitivity to catecholamines.
*Stimulates gut motility.
*Increase bone turnover.
*Increase in serum glucose, decrease in serum
The endocrine disorders in general can be manifested
by either excess or deficiency in the secreting
Common problem related with thyroid
5) Thyroid neoplasia
Leading cause of anterior neck masses.
- Most common neoplastic condition
- Male predominance
- Higher incidence of malignancy
- Female predominance
- Mostly benign
Investigation of thyroid disease:
• TSH level
• Free T4 level
• Free T3 level
• Thyroid antibodies (anti-thyroglobuline antibodies, anti-
• Thyroid ultrasound (U/S neck)
• Radio active iodine uptake
• Thyroid biopsy (FNA)
Fine needle aspiration cytology (FNAC):
* For discrete thyroid swelling.
* Best done under US guidance.
* The only disease that cant be diagnosed by FNA is
The uptake by the thyroid of a
low dose of either:
-Radiolabelled iodine ( I 123)
- technetium (Tc 99)
will demonstrate distribution of
activity in the whole gland.
-Non specific term to indicate
diffuse enlargement of
- Its only enlargement.
- The most common
presentation of a goiter case is
painless mass in the neck.
Classification of Goitres
- No hormonal
and therefore no
(graves dis.) or
nodule or on the top
As many thyroiditis
Clinical assessment of simple goiter:
- Benign disease, colloid goiter, euthyroid , female (3rd
-Presented as mild enlargement of the gland, most of the time
-Complication might develop due to mass effect like tracheal
compression or voice changes, but mostly asymptomatic.
-Acute development—Hemorrhage or cyst >> acute pain
** investigation :
2.neck & chest x-ray
3. dx invest :US & FNAC
Prevention and treatment:
1) Iodine uptake: Iodination of salt
2) T4 administration.
Toxic multinodular goiter:
- Results from disorganized response of the gland to
stimulation and contains areas of hyperplasia and
hypoplasia side by side.
These nodules are usually necrotic and hemorrhagic.
- The commonest presentation is solitary nodule.
- 20% risk of malignancy
Thyroid Uptake Scans
(Technetium 99) –Scintigraphy
(B) Graves disease: diffuse
increased uptake in both thyroid
(C) Toxic multinodulargoiter
(TMNG): “hot”and “cold”areas of
(D) Toxic adenoma: increased
uptake in a single nodule with
suppression of the surrounding
(E) Thyroiditis: decreased or
* Unilateral total
* Frozen section
* Surgery for
Subtotal vs total
Solitary thyroid nodule:
Are common, being a feature of
many different thyroid diseases
The essential clinical problem,
particularly when the lesion is
Solitary, is to distinguish between
Benign and Malignant disease
Assessment of the thyroid nodule
- A nodule in hyperthyroid patient is highly unlikely
to be malignant.
- Dominant nodule in MNG : Malignancy rate may
approach that of solitary nodule 20%
Size ,pain ,age ,previous neck radiation
Consistency of the nodule(hard ,fixed)
Hormone administration Very little evidence to affect
Indications for surgery
Clinical features and suspicious or definite FNAC
If continue enlarge despite TSH suppression
Rare: Less than 1% of all malignancies
Wide spectrum of biological behavior
If treated appropriately there is high survival rate
Iodine rich areas
Affects children and young adults more, F>M.
Previous neck irradiation
It has lymphatic spread more than blood
(the cervical lymph glands may be palpable long before the
primary lesion in the thyroid become palpable)
It could be intra, extra thyroid or multicentric.
Clinical presentation: nodule with or without cervical
lymphoadenopathy, voice changes, airway obstruction if
Dx: clinical assessment and FNAC
Higher incidence in iodine deficient areas
Low association with radiation.
Female to male ratio 3:1
Affects older age group
Stimulated by TSH
The cells in this tumor retain their normal follicular
configuration, encapsulated and solitary.
Spreads by blood stream to the brain, bone, lung..
It is not diagnosed by FNA
Dx: frozen section
Tt: total thyroidectomy. 31
This is the worst type being poorly differentiated and
Peak incidence 60-80 years
Females more than males
Rapid local tissue infiltration
Rapid blood metastasis
-Long standing goiter-rapid changes in voice and
FNAC is diagnostic
Surgery, radiotherapy, chemotherapy
Treatment of differentiated thyroid carcinoma:
*Total Thyroidectomy is the treatment of choice.
Eradicate the primary tumor
Reduce the incidence of metastasis
Facilitate treatment of metastasis
Post operative treatment
• Sensitive indicator for residual or recurrent tumor
• Detect metastatic disease
- Suspected or proven malignancy.
- Tracheal/ esophageal compression
- Cold nodule for Graves’ Disease
- When I131 is contraindicated (pregnancy)
- Large Goiters less likely to respond to ATD or I131.
1) the patient should be euthyroid to decrease the risk of
(Give PTU +/- beta-blocker before surgery. PTU is better
pre-surgical prophylaxis because it additionally blocks
peripheral conversion of T4 to T3).
2) Vocal cords should be checked
3) Patient should be warned for post op complication
4) stable (cold) iodine treatment to decrease gland
vascularity (usually administer 10 to 14 days before
5) beta-blocker therapy
Generally, antithyroid drug therapy should be
administered until thyroid functions normalize (4-8 wk).
•Solitary benign nodule requires lobectomy
•Cancer requires total thyroidectomy
•Thyrotoxicosis or large multinodular goiter
requires subtotal or total thyroidectomy
Acute life threatening, hypermotabolic
Caused by excessive release of thyroid
Features: fever, tachycardia,
neurological, GI disturbance
Function of PTH
- increases serum calcium ( bone
resorption, increasing renal absorption of
calcium, and stimulating the synthesis of
the biologically active form of vitamin D
(1,25-dihydroxy vitamin D)
- increases renal excretion of phosphorous.
- Lead to hypocalcemia
Hypocalcemia ( transient or permanent)
Direct trauma to the parathyroid glands,
devascularization of the glands, or
removal of the glands during surgery.
Review symptoms and thyroid function test
every 4 to 6 week until thyroid levels are
stabilized on a low dose of antithyroid
thyroid function at least every 3 months for the
first year. After 12-18 months, stop antithyroid
medication or decrease it in patients with Graves
hyperthyroidism to determine if the patient has
gone into remission.