Hypothyroidism (Study Outline) For study only—this is not me…

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Hypоthyrоidism (Study Outline) Fоr study only—this is not medicаl аdvice or а substitute for professional care. 1. Background Definition:A clinical syndrome resulting from deficient production of thyroid hormones (T₄ and T₃) or impaired action at the tissue level. Pathophysiology: Primary hypothyroidism (most common): failure of the thyroid gland → ↑ TSH, ↓ free T₄. Secondary (central): pituitary dysfunction → ↓ TSH and ↓ T₄. Tertiary: hypothalamic failure (↓ TRH). Common Causes (Primary): Autoimmune (Hashimoto thyroiditis) – most common in the U.S. Iatrogenic: post-thyroidectomy, radioactive iodine, or antithyroid medications. Iodine deficiency or excess. Congenital hypothyroidism (thyroid dysgenesis, enzyme defects). Drugs: lithium, amiodarone, interferon-α, tyrosine kinase inhibitors. Epidemiology: More common in women and older adults. Hashimoto’s thyroiditis often associated with other autoimmune disorders (e.g., type 1 DM, pernicious anemia). 2. History Symptoms (Gradual Onset): Fatigue, weakness, cold intolerance. Weight gain despite decreased appetite. Constipation. Dry skin, hair loss, brittle nails. Depression, memory impairment, slowed thinking. Menstrual irregularities, infertility. Severe Forms: Myxedema: severe, long-standing hypothyroidism → nonpitting edema, facial puffiness, hoarseness, periorbital swelling. Myxedema coma: life-threatening decompensation with hypothermia, bradycardia, hypotension, and hypoventilation (precipitated by illness or sedatives). Historical Clues: Prior thyroid surgery or radioactive iodine therapy. Family history of autoimmune disease. Recent medication changes (e.g., lithium, amiodarone). 3. Exam Findings General: Fatigued appearance, weight gain, coarse dry hair, pallor. Skin: Cool, dry, thickened skin; nonpitting edema (myxedema). Cardiovascular: Bradycardia, diastolic hypertension, pericardial effusion (severe). Neurologic: Delayed relaxation of deep tendon reflexes (especially Achilles). HEENT: Puffy face, periorbital edema, enlarged or atrophic thyroid. Other: Macroglossia, hoarseness, carpal tunnel syndrome. Pediatric Findings: Growth retardation, delayed bone age, developmental delay if congenital. 4. Making the Diagnosis Initial Test (Gold Standard): Serum TSH — most sensitive screening test. Interpretation: Primary hypothyroidism: ↑ TSH, ↓ free T₄. Secondary (pituitary): ↓ or inappropriately normal TSH, ↓ free T₄. Subclinical hypothyroidism: mildly ↑ TSH with normal free T₄. Autoimmune Confirmation: Positive anti-thyroid peroxidase (anti-TPO) or anti-thyroglobulin antibodies → Hashimoto thyroiditis. Other Findings: Lipid abnormalities: hypercholesterolemia, ↑ LDL. Hyponatremia: due to decreased free water clearance. Anemia: normocytic or macrocytic. Imaging: Thyroid ultrasound: heterogenous or atrophic gland (Hashimoto). MRI of pituitary: indicated if secondary hypothyroidism suspected. 5. Management (Exam Concepts) (Conceptual overview only—no dosing or treatment directives.) General Principles: Thyroid hormone replacement (e.g., levothyroxine) is standard. Primary hypothyroidism: lifelong replacement and regular TSH monitoring. Secondary hypothyroidism: monitor free T₄, not TSH, for adjustment. Special Situations (Conceptual): Myxedema coma: medical emergency—requires ICU care and supportive management. Pregnancy: increased thyroid hormone requirement; check TSH each trimester. Exam Tip: Drug-induced hypothyroidism → lithium, amiodarone. Most sensitive test: serum TSH. Hashimoto thyroiditis: firm, irregular, painless goiter + positive anti-TPO antibodies. Monitoring: Reassess TSH every 6–8 weeks after dose adjustment. Evaluate for improvement in symptoms, energy, and metabolic parameters.   QUESTION A 45-year-old woman presents with fatigue, weight gain, and constipation. Physical exam shows dry skin, bradycardia, and delayed relaxation of deep tendon reflexes. Laboratory results reveal TSH 9.8 mIU/L (elevated) and free T₄ below normal. Which of the following additional findings is most likely? A. Elevated anti-thyroid peroxidase (anti-TPO) antibodiesB. Elevated free T₃ and suppressed TSHC. Elevated serum calcium and decreased phosphateD. Decreased LDL cholesterol  

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Pаssаge Five (Questiоns 50 - 53) Cuаndо el niñо estudiaba su carrera sucedió uno de esos cambios que tan comunes son en la edad juvenil. De perezoso se volvió trabajador. Cumplía bien sus deberes escolásticos. No sólo iba a clase puntualmente, sino que se ponía en la primera fila para mirar mejor al profesor. Al terminar la clase el niño era uno de los que interrumpían al profesor para pedirle que les explicara un punto oscuro de la lección.   Después de la clase el niño hacía que el maestro le aclarara lo difícil de la lección