Hаshimоtо Thyrоiditis (Chronic Lymphocytic Thyroiditis) (Study Outline) For study only—this is not medicаl аdvice or a substitute for professional care. 1. Background Definition:Autoimmune destruction of the thyroid gland leading to chronic hypothyroidism.It is the most common cause of primary hypothyroidism in iodine-sufficient regions (e.g., the U.S.). Pathophysiology: Autoantibodies target thyroid antigens, primarily thyroid peroxidase (anti-TPO) and thyroglobulin (anti-Tg). Lymphocytic infiltration with formation of germinal centers leads to gradual destruction of thyroid tissue. Over time → decreased T₄/T₃ synthesis, elevated TSH, and permanent thyroid failure. Early in disease, transient thyrotoxicosis (“Hashitoxicosis”) can occur due to release of preformed thyroid hormones. Epidemiology: Most common in middle-aged women (30–60 years). Associated with other autoimmune disorders: type 1 diabetes, Addison disease, pernicious anemia, celiac disease, vitiligo. Genetic predisposition: linked to HLA-DR3 and HLA-DR5. 2. History Typical Symptoms (Gradual Onset): Fatigue, weight gain, cold intolerance. Constipation, dry skin, hair loss, brittle nails. Depression, slowed thinking, memory issues. Menstrual irregularities, infertility. Voice changes, neck fullness, dysphagia (from goiter). Early “Hashitoxicosis” Phase: Transient symptoms of hyperthyroidism (anxiety, heat intolerance, palpitations) due to hormone leakage from damaged follicles. Historical Clues: Family history of autoimmune thyroid disease. Previous thyroid enlargement (“goiter”) followed by gradual slowing of metabolism. 3. Exam Findings General: Tired appearance, weight gain, dry coarse hair and skin. Thyroid Exam: Firm, rubbery, non-tender, diffusely enlarged thyroid in early stages. May become atrophic over time due to fibrosis. Skin: Cool, pale, dry. Cardiovascular: Bradycardia, diastolic hypertension. Neurologic: Delayed relaxation of deep tendon reflexes. HEENT: Puffy face, periorbital edema, hoarse voice (from myxedema). Late Stage: Myxedema signs, macroglossia, and generalized slowing of activity. 4. Making the Diagnosis Initial Test (Gold Standard): Serum TSH — elevated (primary hypothyroidism). Confirmatory Findings: ↓ Free T₄, sometimes ↓ T₃. Positive anti-thyroid peroxidase (anti-TPO) and/or anti-thyroglobulin (anti-Tg) antibodies → diagnostic hallmark. Additional Laboratory Findings: Mild hypercholesterolemia (due to reduced LDL clearance). Normocytic or macrocytic anemia. Hyponatremia possible due to impaired free water excretion. Imaging (if indicated): Thyroid ultrasound: diffuse heterogeneity and hypoechogenicity (“moth-eaten” appearance). Fine-needle aspiration (FNA): lymphocytic infiltration, Hurthle cells (oncocytic metaplasia). Diagnostic Pattern: ↑ TSH + ↓ T₄ + positive anti-TPO antibodies = Hashimoto thyroiditis. 5. Management (Exam Concepts) (Conceptual overview only—no dosing or treatment regimens.) General Principle: Thyroid hormone replacement (levothyroxine) for symptomatic or overt hypothyroidism. Monitoring: Reassess TSH every 6–8 weeks after initiating or adjusting therapy. Once stable, check annually. Complications: Myxedema coma: life-threatening hypothyroid crisis in severe, untreated disease. Goiter enlargement may cause local compressive symptoms. Increased risk of thyroid lymphoma (especially if longstanding Hashimoto’s). Exam Tips: Firm, painless goiter + anti-TPO antibodies → classic for Hashimoto thyroiditis. Thyroiditis progression: transient thyrotoxic phase → euthyroid → permanent hypothyroid. Differentiate from subacute thyroiditis: Hashimoto is painless and chronic; subacute is painful and self-limited. QUESTION A 42-year-old woman presents with fatigue, weight gain, and cold intolerance. Physical exam reveals a firm, non-tender, diffusely enlarged thyroid gland. Laboratory results show TSH 11.2 mIU/L (elevated) and free T₄ below normal. Which of the following findings would most likely confirm the diagnosis? A. Positive thyroid-stimulating immunoglobulins (TSI)B. Positive anti–thyroid peroxidase (anti-TPO) antibodiesC. Decreased serum thyroglobulin concentrationD. Diffuse increased radioactive iodine uptake