The Endocrine System - Chapter 13 PDF

# CHAPTER (13) ## THE ENDOCRINE SYSTEM ### ILOS: After this lecture student should be able to: - Discuss the pathological features of Grave's disease - Describe types of thyroiditis. - Describe pathology of goiter. - Describe the pathological types of thyroid tumors; - Describe effects and complica...

# CHAPTER (13) ## THE ENDOCRINE SYSTEM ### ILOS: After this lecture student should be able to: - Discuss the pathological features of Grave's disease - Describe types of thyroiditis. - Describe pathology of goiter. - Describe the pathological types of thyroid tumors; - Describe effects and complications of Diabetes Mellitus - Explain types of primary Diabetes Mellitus - Describe pathology of common benign & malignant adrenal medullary neoplasia. - Discuss pituitary tumors ## THE THYROID GLAND ### THYROIDITIS - Definition: Inflammation of the thyroid gland. - Types: - Infectious Thyroiditis: Rare - Autoimmune Thyroiditis: Hashimoto Thyroiditis - Others: - Granulomatous (de Quervain) thyroiditis. - Reidel's thyroiditis. ### ❖ HASHIMOTO THYROIDITIS (CHRONIC LYMPHOCYTIC THYROIDITIS) - Definition: - It is an autoimmune disease characterized by thyroid enlargement with intense lymphocytic infiltration of the thyroid. Hashimoto thyroiditis is characterized by gradual thyroid failure because of autoimmune destruction of the thyroid gland. - Etiology & pathogenesis: - Hashimoto thyroiditis is an autoimmune disease directed against thyroid antigens. - Autoimmune injury is mediated by circulating antibodies to thyroglobulin and thyroid peroxidase. - Thyroid autoimmunity is accompanied by progressive follicular cell loss, mononuclear cell infiltration, and fibrosis. - Morphology: - Gross: - The thyroid is often diffusely enlarged. - The capsule is intact. - The cut surface is pale, yellow tan, firm, and vaguely nodular. - Microscopic: - Extensive infiltration of the parenchyma by a mononuclear inflammatory infiltrate containing small lymphocytes, plasma cells, and well-developed germinal centers. - The thyroid follicles are atrophic and are lined in many areas by epithelial cells distinguished by the presence of abundant eosinophilic, granular cytoplasm, termed Hürthle cells. - Delicate fibrosis. - Clinical picture: - Painless enlargement of the thyroid. - In the usual clinical course, hypothyroidism develops gradually. In some cases, however, it may be preceded by transient thyrotoxicosis caused by disruption of thyroid follicles, with secondary release of thyroid hormones. - Complications: - Increased risk for the development of B-cell non-Hodgkin lymphomas and papillary thyroid carcinomas. ### ❖ SUBACUTE GRANULOMATOUS (DE QUERVAIN) THYROIDITIS. - Subacute thyroiditis is attributed to a viral infection or post viral inflammatory process, resulting in cytotoxic T-cell-mediated follicular epithelial damage. Because the immune response is virus initiated, it is self-limited. - Morphology: - Gross: - Unilaterally or bilaterally enlarged firm gland. - On cut section, the involved areas are firm and yellow-white. - Microscopic: - Early thereare neutrophils, forming microabscesses. - Later, there are aggregates of lymphocytes, activated macrophages, and plasma cells and multinucleate giant cells. - Later fibrosis occurs. - Clinical Picture: - Painful enlarged thyroid gland. ### RIEDEL THYROIDITIS. - It is a rare form of thyroiditis of unknown etiology. - It characterized by extensive fibrosis involving the thyroid and contiguous neck structures. - The presence of a hard and fixed thyroid mass clinically simulates a thyroid carcinoma. ## GRAVE'S DISEASE - Definition: - Grave's disease is an autoimmune disorder characterized by thyrotoxicosis. An infiltrative ophthalmology is present in 40% of patients, and pretibial myxedema in a minority of patients. - It is more common in women of age 20-40. There is a genetic susceptibility. - Pathogenesis: - Grave's disease is characterized by production of autoantibodies to TSH receptor. - 1- Thyroid-stimulating immunoglobulin (TSI): binds to the TSH receptor and mimics the action of TSH, leading to T3 and T4 release. - 2- Thyroid growth-stimulating immunoglobulin (TGI): is also directed against TSH receptor, but these autoantibodies induce thyroid follicular epithelium proliferation. - The characteristic infiltrative ophthalmopathy, occurring in 40% of patients is a T cell mediated autoimmunity. The exact antigen is not clear. - Morphology: - Gross: The thyroid gland is mildly and symmetrically enlarged with smooth surface, fleshy and red in color due to increased vascularity. - Microscopic: - The thyroid gland showed: - 1- Diffuse hyperplasia of follicular epithelium, showing crowding into irregular papillary folds. - 2- Colloid is decreased. - 3- Between the follicles there is accumulation of lymphocytes with lymphoid follicle formation and increased numbers of blood vessels. - Grave's ophthalmopathy is characterized by T lymphocyte infiltration, edema and accumulation of hyaluronic acid and chondroitin sulphate in extra-orbital muscles and retro-orbital tissue. The result is protrusion of the eyeball forwards (exophthalmos) and interference of function of extra-occular muscles. Pretibial myxedema shows same features as the ophthalmopathy. - Clinical picture: - 1- Thyrotoxicosis - 2- The ophthalmopathy may be complicated by corneal injury. ## GOITER - Definition: Goiter is a non-inflammatory, non-neoplastic enlargement of the thyroid gland. - Pathogenesis: - There is impaired synthesis of thyroid hormone, most commonly due to iodine deficiency, leading to compensatory increased production of TSH. - TSH causes hyperplasia of thyroid follicular cells and enlargement of the thyroid gland. The hyperplasia is enough to overcome the deficiency and maintain euthyroid state. - Goiter can be endemic or sporadic. - 1- Endemic Goiter: Affects 10% of population in areas away from the sea like mountains, due to deficiency of iodine in soil, water and food. - 2- Sporadic goiter: Affects females more than males, with a peak incidence in young adulthood when there is physiological increase in demand for thyroxin. - Morphology: - It passes in 3 phases: - 1. Diffuse simple goiter: - First there is hyperplasia in response to increased TSH, and the follicles are lined by crowded columnar cells, which may form projections inside the follicles - Gross: The thyroid gland is diffusely and symmetrically enlarged. The patient is euthyroid. - 2. Colloid goiter: - If the demand for thyroid hormone decreases or iodine deficiency is corrected, the follicular epithelium involutes. The follicles contain abundant colloid and the lining follicular cells are flattened. - Gross: The gland is diffusely, symmetrically enlarged. The cut surface is brown, glassy, and translucent. - 3. Multinodular Goiter: - With time, recurrent episodes of hyperplasia and involution produce a more irregular enlargement of the thyroid. - Gross: - Multinodular goiter shows asymmetric enlargement of the thyroid glands and can be massively enlarged. - Cut section reveals variable-sized nodules containing variable amounts of brown gelatinous colloid, with areas of fibrosis, hemorrhage, calcification, and cystic change. - Microscopically: - The gland appearance is variable with nodules formed of follicles having flattened epithelium and filled with colloid alternating with other nodules showing hyperplastic lining and little colloid. The nodules are separated by fibrous tissue. Areas of calcification and hemorrhages are seen. - Effect and Complications: - 1. Cosmetic effects of a large neck mass. - 2. Airway obstruction. - 3. Dysphagia. - 4. A hyperfunctioning nodule may develop within a long-standing goiter resulting in hyperthyroidism (Toxic nodular goiter). ## THYROID NEOPLASMS - **Benign tumors** - Follicular adenoma - **Malignant tumors** - 1. Papillary carcinoma. Most common. - 2. Follicular carcinoma. - 3. Anaplastic (undifferentiated) carcinoma. - 4. Medullary carcinoma (from parafollicular C cells). ### FOLLICULAR ADENOMA: - Definition: Benign epithelial tumor arising from thyroid follicular epithelium. - Gross: - Solitary, spherical, encapsulated lesion that is well demarcated from the surrounding thyroid parenchyma. - Average about 3 cm in diameter. - The color ranges from gray-white to red-brown. - Occasionally with fibrosis, hemorrhage, or calcification. - Microscopic: Compact, small follicles lined by cubical cells, surrounded by a fibrous capsule. - Clinical picture: - A solitary thyroid nodule. - Rarely, functional adenoma producing thyrotoxicosis.