Internal Medicine (Theory) · MU Sofia

55. Hypothyroidism – Myxedema

Covers hypothyroidism and myxedema, starting with primary and secondary forms and the rare, life-threatening myxedema coma. It then goes through causes (autoimmune, congenital, iatrogenic), the pathogenesis of myxedema, and symptoms separately for infants, adults and coma. Diagnosis follows with a laboratory pattern for primary versus secondary disease, then treatment with lifelong levothyroxine and emergency management of coma, and finally complications.

Inside: 8 sections · 5 labelled pictures · 14 flashcards · 3 min

Topic 52 of 58 in the MU Sofia syllabus for Internal Medicine (Theory) (Medicine, Year 3). The free AceMed note covers it in 8 sections, about 427 words (3 min of reading), with 14 flashcards.

In this note

  1. Hypothyroidism – Myxedema
  2. Definition
  3. Etiology
  4. Pathogenesis
  5. Symptoms
  6. Diagnosis
  7. Treatment
  8. Complications

Definition

Hypothyroidism is a condition where the thyroid gland fails to produce sufficient thyroid hormones (T3, T4), resulting in a general slowing of metabolic processes.

  • Primary hypothyroidism: dysfunction at the level of the thyroid gland (most common)
  • Secondary hypothyroidism: due to pituitary or hypothalamic dysfunction, leading to reduced TSH or TRH production
  • In severe cases, especially in elderly patients, it may progress to a myxedema coma – a rare, life-threatening state.

Etiology

1. Primary Hypothyroidism (thyroid gland itself affected):

  • Autoimmune causes:
  • Hashimoto's thyroiditis – most common cause in developed countries; leads to lymphoid infiltration, atrophy, and fibrosis
  • Atrophic thyroiditis – autoantibodies destroy thyroid tissue without goiter
  • Postpartum thyroiditis – transient form following childbirth
  • Congenital causes:
  • Agenesis or dysgenesis of the thyroid gland
  • Dyshormonogenesis (enzyme defects in hormone synthesis)
  • Iodine deficiency
  • Iatrogenic:
  • After thyroidectomy or radioactive iodine therapy
  • Antithyroid drugs

2. Secondary Hypothyroidism:

  • Pituitary or hypothalamic disease → ↓ TSH (e.g., tumors, trauma, Sheehan's syndrome)

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