PAL2 Thyroid Pathology

• Thyroid gland

  2 lateral lobes connected by isthmus, below & anterior to larynx, normal weight: 20-30gm, function: synthesize thyroxine (T4) & triiodothyronine (T3) by follicular epithelial cells, T4 & T3 exert negative feedback on TSH, C-cells: parafollicular cells synthesize calcitonin involved in calcium metabolism

  
• Thyroid gland

  • Apart from TSH, another hormone regulates the gland

  
• Why should we study thyroid pathology?

  
• Why do you need to study histological features of thyroid pathology?

  
• Thyroid disorders

  • Hyperthyroidism
  • Hypothyroidism
  • Thyroiditis
  • Diffuse & Multinodular Goitre
  • Neoplasms

  
• Hyperthyroidism

  Excess thyroid hormones; T3, T4, normal TSH level in adult is 0.4-4.0 mIU/L, normal T4 level is 5.0-11.0 ug/dl

  
• Causes of hyperthyroidism

  • Graves disease: Diffuse toxic goitre (85%)
  • Toxic multinodular goitre
  • Functioning toxic adenomas
  • Thyroiditis
  • Exogenous administration
  • Iodine induced
  • Struma ovarii
• Graves disease

  Autoimmune disease, autoantibodies production to TSH receptor (thyroid stimulating immunoglobulin - TSI) binds to TSH receptor and mimics its action, leading to increased thyroid hormone production
• Graves disease

  • Diagnosis: serum T3, T4 increased, TSH decreased, serum thyroid receptor antibody increased, increased uptake of radioactive iodine

  
• Graves disease

  • Triad of findings: hyperthyroidism due to diffuse hyperfunctional enlargement of thyroid, infiltrative ophthalmopathy (exophthalmos), infiltrative dermopathy (pretibial myxedema)
• Graves disease
• Graves disease (gross)

  • Symmetrically enlarged gland, weight may be >80 grams, soft meaty appearance of the parenchyma on cut surface

  
• Graves disease (histology)

  • Crowded and tall follicular cells, formation of small papillae filling the lumen of the follicles (papillae do not contain fibrovascular cores), pale colloid with scalloped margins, lymphoid infiltrate with germinal centers common
• Hypothyroidism

  Decrease in thyroid hormones, causes include iodine deficiency, autoimmune (Hashimoto Thyroiditis), developmental, drugs, radiation/surgery ablation, pituitary/hypothalamic disorders
• Hypothyroidism

  • Diagnosis: serum T3, T4 decreased, serum TSH increased in primary, normal in secondary

  
• Cretinism

  Impaired skeletal and CNS functions, mental retardation, short stature, protruding tongue, umbilical hernia, occurs if mother is hypothyroid before development of thyroid
• Myxoedema


  Slowing of speech, cold intolerance, decreased exercise capacity, deep voice, accumulation of glycosaminoglycans & hyaluric acid in subcutaneous tissue
• Types of thyroiditis

  • Hashimoto Thyroiditis
  • Subacute Lymphocytic (Painless) Thyroiditis
  • Subacute Granulomatous (de Quervain) Thyroiditis
  • Riedel Thyroiditis

  
• Hashimoto Thyroiditis

  Autoimmune disease, auto-antibodies production (anti-thyroglobulin antibody, anti-peroxidase antibody) leading to destruction of thyrocytes and replacement of thyroid parenchyma by lymphocytic infiltrate & fibrosis, initial hyperthyroidism followed by hypothyroidism
• Hashimoto Thyroiditis (gross)

  • Diffuse enlargement, firm, rubbery, cut surface pale, yellow-tan, nodular, or symmetrical small thyroid (atrophy)

  
• Hashimoto Thyroiditis (histology)

  • Lymphocytic infiltration, plasma cells & lymphoid follicle formation, atrophy of thyroid follicle, oncocytic change, decrease in colloid, fibrosis
• Subacute granulomatous (De Quervain) thyroiditis

  Painful, viral infection, high T4 & T3, low TSH, chronic inflammatory cells with multinucleate giant cells infiltration - granulomatous inflammation
• Subacute lymphocytic thyroiditis

  Painless, autoimmune, occurs after pregnancy (post-partum), anti-thyroid peroxidase antibody positive, transient hyperthyroidism

  
• Filtration

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• Plasma cells


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• Lymphoid follicles with germinal centre


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• Thyroid follicles

  • Atrophic, many lined by Hurtle cells/ oncocyte having abundant eosinophilic granular cytoplasm

  
• Colloid

  • Decreased
• Fibrosis

  • Increased
• Gross: Diffusely, symmetrically enlarged, smooth and firm. Cut surface pale, gray-tan and firm (resembling lymph node)
• Antibodies detected: Anti-peroxidase, Anti-thyroglobulin
• Figure 18 Histology of Hashimoto thyroiditis
• Thyroiditis

  Subacute granulomatous (De Quervain) thyroiditis

  
• Subacute granulomatous (De Quervain) thyroiditis

  Painful, viral infection eg coxsackie, mumps, measles adenovirus
• Subacute granulomatous (De Quervain) thyroiditis

  40 & 50, women commoner

  
• Subacute granulomatous (De Quervain) thyroiditis

  High T4 & T3, low TSH

  
• Subacute granulomatous (De Quervain) thyroiditis


  • Chronic inflammatory cells with multinucleate giant cells infiltration -- Granulomatous inflammation

  
• Figure 19 Subacute granulomatous thyroiditis

  
• Thyroiditis

  Subacute lymphocytic thyroiditis

  
• Subacute lymphocytic thyroiditis

  Painless, autoimmune