• Thureoeides (Ancient Greek), meaning ‘Sheild
• Anterior aspect of neck.
• Two lobes connected by isthmus.
• Endocrine gland.
• Regulates BMR, stimulates somatic and psychic
growth, calcium metabolism.
• Floor of primitive pharynx, caudal to tuberculum
impar. (Marked by foramen caecum of tongue)
• Median endodermal thyroid diverticulum
• Downward growth, bifurcates and forms lobes.
• Weight: About 25g (Larger in Females).
• Lies against C5, C6, C7 and T1 vertebrae.
• Lobes: Middle of thyroid cartilage to IV or V tracheal
• Isthmus: II – IV tracheal ring.
• Dimensions (cm): Lobe – 5 × 2.5 × 2.5
Isthmus – 1.2 × 1.2
Capsules of Thyroid
• True capsule: condensed peripheral connective
tissue of the gland.
• False capsule: derived from pretracheal layer of
deep cervical fascia. (Ligament of Berry)
• Radiation : Proloned exposure to high dose of external
radiation or radioiodine. Children and young adults.
• Iodine excess and TSH
– Papillary thyroid carcinoma:•
External radiation or radioactive iodine therapy
Iodine sufficient areas.
Common in children and females.
RET overexpression (chr 10)
– 20% cases
– Tyrosine kinase receptor targeted by tumor promoting factors
• NTRK1 rearrangement
• Elevated TSH , Hormone dependent tumor.
• Hushimotos thyroiditis
– Follicular thyroid carcinoma:- agressive
• Common in females
• Iodine-deficient areas
• 50% cases with RAS oncogene mutation
• Gene translocation:- PAX- 8 and PPARγ-1
• De novo or Pre-existing Multinodular goitre
Hurthle cell carcinoma:variant of follicular thyroid carcinoma.
Abundant oxyphill cells
Spread more commonly to regional lymph nodes.
Vascular or capsular invasion.
– Medullary thyroid carcinoma:
• Origin:- parafollicular C-cells.
• Site:- Superolaterally in the thyroid lobes.
• RET gene mutation, familial and sporadic
• Associated with MEN II syndrome and pheochromocytoma with
hypertention. MCT associated with MEN II B with pheochromocytoma
(Sipple’s disease) is most aggressive.
• Not TSH dependant and does not take up radioactive iodine.
– Anaplastic thyroid carcinoma:- very aggressive
• Common in women 7th to 8th decade of life.
• Origin- dedifferentiation of differentiated PTC or FTC, or
Inactivating point mutation in p53 gene.
– Malignant Lymphoma
• NHL type
• Occurs in pre-existing Hushimoto’s thyroiditis
Middle to old
Middle to old