A patient with autoimmune thyroiditis presents with hypothyroidism. Which of the following is true?
Ref: Robbins Pathologic Basis of Disease, 8th: editionExplanation:HASHIMOTO THYROIDITISMost common cause of hypothyroidism in areas of the world where iodine levels are sufficient. Gradual thyroid failure due to autoimmune destruction of the thyroid gland.Common age group (45 - 65)Female predominance (10: 1 to 20: 1)Can occur in children and is a major cause of nonendemic goiter.It is associated with polymorphisms in multiple immune regulation-associated genes, the most significant of which is the linkage to cytotoxic T lymphocyte--associated antigen-4 (CTLA4) polymorphisms & Also functional polymorphism in protein tyrosine phosphatase-22 fPTPN22J gene that encodes a lymphoid tyrosine phosphatase, which is also thought to inhibit T- cell function.Susceptibility to other autoimmune diseases, such as type 1 diabetes has been associated w ith polymorphisms in both Cl'LA 4 and PTPN22.PathogenesisHashimoto thyroiditis is caused by a breakdown in self-tolerance to thyroid auto-antigens.presence of circulating autoantibodies against thyroglobulin and thyroid peroxidaseInduction of thyroid autoimmunity is accompanied by a progressive depletion of thyrocytes by apoptosis and replacement of the thyroid parenchyma by mononuclear cell infiltration and fibrosis.MorphologyDiffusely enlargedThe capsule is intact, and the gland is well demarcated from adjacent structures. .Microscopic examination reveals extensive infiltration of the parenchyma by a mononuclear inflammatory infiltrate containing small lymphocytes, plasma cells, and w ell-developed germinal centersThe thyroid follicles are atrophic and are lined in many areas by epithelial cells distinguished by the presence of abundant eosinophilic, granular cytoplasm, termed Hurthle cells. This is a metaplastic response of the normally low cuboidal follicular epithelium to ongoing injury.In fine-needle aspiration biopsy samples, the presence of Hurthle cells in conjunction with a heterogeneous population of lymphocytes is characteristic of Hashimoto thyroiditis.In "classic'" Hashimoto thyroiditis, interstitial connective tissue is increased and may be abundant.A fibrous variant is characterized by severe thyroid follicular atrophy and dense "keloid - like*' fibrosis, broad bands of acellular collagen encompassing residual thyroid tissue.Unlike Reidel thyroiditis, the fibrosis does not extend beyond the capsule of the gland. The remnant thyroid parenchyma demonstrates features of chronic lymphocytic thyroiditis.Clinical CoursePainless enlargement of the thyroid associated with some degree of hypothyroidismThe enlargement of the gland is usually symmetric and diffuseIn some cases, however, it may be preceded by transient thyrotoxicosis caused by disruption of thyroid follicles, with secondary release of thyroid hormones ("hashi toxicosis"). During this phase, free T4 and T3 levels are elevated, TSH is diminished, and radioactive iodine uptake is decreased.As hypothyroidism supervenes. T4 and T3 levels fall, accompanied b\ a compensatory increase in TSH.Increased risk for developing other autoimmune diseases- Endocrine (type 1 diabetes, autoimmune adrenalitis)- Nonendocrine (systemic lupus erythematosus. myasthenia gravis, and Sjogren syndrome)Increased risk for the development of B-eell non-Hodgkin lymphomas, especially marginal zone lymphomas of mucosa-associated lymphoid tissuesThe relationship between Hashimoto disease and thyroid epithelial cancers remains controversial, with some morphologic and molecular studies suggesting a predisposition to papillary carcinomas.
Thyroid peroxidase antibodies
Painful enlargement of thyroid
More common in men
No risk, of malignancy
Disorders of Thyroid Metabolism