Thyroid Diseases

• Bi-lobed organ located adjacent to the thyroid cartilage at the level of C4, 5, 6 and T1
• Develops from a midline diverticulum in the floor of the pharynx at the foramen cecum
• Descends to the neck and initially attaches to the pharynx by the thyroglossal duct
• A pyramidal lobe sometimes develops at the distal end of the remnant of the thyroglossal duct
• Both lobes are joined together in the midline by the isthmus
• The gland is surrounded by the pre-tracheal fascia closely attached to the cricoid cartilage
• Anterior to the fascia is the sternothyroid, then the sternohyoid muscles
• Relations: Recurrent laryngeal nerve / Superior laryngeal nerve / Parathyroid gland

Blood supply

• Superior thyroid artery
• Inferior thyroid artery

Venous drainage

• Superior and middle thyroid veins into internal jugular
• Inferior veins into brachiocephalic vein

Lymphatic drainage

• Cervical group of lymph nodes

• Produces:
  • Thyroxin (T4)
  • Triiodothyronine (T3)
  • Calcitonin
• Regulated by:
  • Hypothalamic-pituitary-thyroid axis
  • Thyroid Stimulating Hormone (TSH)
  • Thyrotropin-releasing hormone (TRH)
  • Blood Calcium level
• T4/T3 Actions:
  • Basal Metabolic rate
  • Growth
  • Cardiac
  • Central and Peripheral nervous system

• Congenital:
  • Thyroglossal cyst
  • Thyroglossal fistula
  • Ectopic thyroid tissue
  • Cretinism
• Inflammatory:
  • Viral
  • Bacterial
  • Autoimmune - Graves' disease / Hashimoto’s thyroiditis
• Neoplastic:
  • Adenoma
  • Carcinoma

• Goitrous / Agoitrous diseases
• Goiter:
  • Enlarged thyroid gland
  • More common in females
  • Diffuse – The whole gland is uniformly enlarged
  • Nodular – Enlargement has one or more nodules
  • Could be classified as:
    • Inflammatory
    • Toxic
    • Hypothyroid
    • Neoplastic
    • Simple
• Inflammatory goiter:
  • Usually diffuse
  • Associated with pain
  • Treated non-surgically except for abscess drainage
• Toxic goiter:
  • Associated with increased secretion of T3/T4
  • TSH level is low
  • Could be diffuse – Graves' disease / Nodular
  • Accompanied by symptoms of hyperthyroidism:
    • Weight loss despite an increased appetite
    • Restlessness / Anxiety / Insomnia / Palpitation / Sweating / Tremors / Oligomenorrhea
    • May be associated with eye signs:
      • Exophthalmos – Protrusion of the eyeballs
      • Eye lid retraction / lid lag / Ophthalmoplegia
    • May be associated with pretibial myxoedema
• Hypothyroid goiter:
  • Rare
  • Iodine deficiency
  • In neonates / childhood
  • Pregnancy / Breastfeeding
• Neoplastic goiter:
  • Differentiated carcinoma:
    • Follicular carcinoma – More common in this environment, commonly associated with hematogenous metastasis
    • Papillary carcinoma – Associated with lymphatic spread
  • Medullary carcinoma:
    • From parafollicular C cells that originate in the neural crest
    • Associated with increased secretion of calcitonin
    • Might be associated with other tumors in MEN 1 / MEN 2
  • Anaplastic carcinoma – Undifferentiated with poor prognosis
• Simple goiter:
  • Commonest
  • Diagnosis of exclusion
  • Diffuse / Nodular / Multinodular
  • Not associated with systemic symptoms
  • Thyroid function is normal
  • No feature of inflammation
  • No feature of neoplasia

CLINICAL PRESENTATION

• Swelling in the anterior triangle of the neck
• Local symptoms:
  • Difficulty in respiration
  • Difficulty in swallowing
  • Voice changes
• Systemic symptoms:
  • Symptoms of hyper secretion or hypo secretion
• Features of metastasis:
  • Lungs / bone

CLINICAL SIGNS

• Anterior neck swelling that moves with deglutition / swallowing
• Does not move with protrusion of the tongue
• Might affect the whole gland uniformly, take the shape of the gland, and feel smooth
• Might affect only one lobe or just the isthmus
• Nodules may be palpable and consistency is important
• Cervical lymphadenopathy might suggest malignancy
• Toxicity is suggested by:
  • Anxious look
  • Tachycardia
  • Warm, wet palms
  • Finger tremors
  • Eye signs
  • Pretibial myxoedema

For diagnsosis

• Neck Ultrasonography:
  • Size / nodularity / nodes / invasion
• Thyroid function test
• Free T3, T4, TSH
• FNAC

Others- for extent/spread, complications, specific cause

• Neck X-ray - AP and Lat View:
  • Soft tissue shadow / Calcification
  • Tracheal compression and deviation
• Thoracic inlet view:
  • Retrosternal extension
• Serum Calcitonin
• Thyroid Autoantibody levels
• Radioactive iodine uptake
• CT scan
• Laryngoscopy

• Drugs - Agoitrous conditions:
  • Symptomatic relief
  • Antithyroid drugs like carbimazole / propyl thiouracil
  • L thyroxine
• Surgery - Goiters:
  • Subtotal Thyroidectomy
  • Total Thyroidectomy
• Radioactive Iodine:
  • Agoitrous toxicity
  • Differentiated malignancy
• External Beam Radiotherapy:
  • Locally advanced malignancy

INDICATIONS FOR SURGERY IN GOITERS

• Cosmesis
• Pressure symptoms
• Toxicity
• Neoplasia

• EARLY
  • Respiratory obstruction
  • Recurrent laryngeal palsy
  • Laryngeal edema
  • Tension Hematoma
  • Voice changes
    • Recurrent laryngeal nerve palsy
    • Superior laryngeal nerve palsy
  • Hypo-parathyroidism
• LATE
  • Hypothyroidism
  • Recurrent goiter
  • Keloids / Hypertrophic scars