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Hypothyroidism

Background knowledge ๐Ÿง 

Definition

  • Hypothyroidism is a condition characterised by insufficient thyroid hormone production.
  • Leads to a generalised slowing down of metabolic processes.

Epidemiology

  • Prevalence in the UK: around 2% of the adult population.
  • Common in older adults and women.
  • Increases with age.
  • More common in those with a family history of thyroid disease.

Aetiology and Pathophysiology

  • Autoimmune (Hashimoto’s thyroiditis).
  • Atrophic thyroiditis
  • Iodine deficiency.
  • Post-thyroidectomy or radioiodine therapy.
  • Medications (e.g., lithium, amiodarone).
  • Secondary hypothyroidism due to pituitary or hypothalamic disorders.

Types

  • Primary hypothyroidism: dysfunction at the thyroid gland level.
    • Thyroid hormone deficiency.
  • Secondary hypothyroidism: pituitary gland dysfunction.
    • TSH deficiency.
  • Tertiary hypothyroidism: hypothalamic dysfunction.
    • TRH deficiency.

Clinical Features ๐ŸŒก๏ธ

Symptoms

  • Fatigue.
  • Weight gain.
  • Cold intolerance.
  • Constipation.
  • Depression.
  • Menstrual irregularities.

Signs

  • Bradycardia.
  • Dry, coarse skin.
  • Hair loss.
  • Periorbital puffiness.
  • Delayed reflexes.
  • Goitre (in some cases).

Investigations ๐Ÿงช

Tests

  • Serum TSH: elevated in primary hypothyroidism, low or normal in secondary.
  • Free T4: low.
  • Thyroid antibodies: anti-TPO and anti-thyroglobulin antibodies in autoimmune thyroiditis.
  • Full blood count and lipid profile.

Management ๐Ÿฅผ

Management

  • Levothyroxine replacement therapy: dose adjusted based on TSH levels.
  • Regular monitoring of TSH and symptoms.
  • Patient education on adherence and symptoms of over- or under-treatment.
  • Follow-up in primary care.

Complications

  • Cardiovascular disease.
  • Myxedema coma (severe hypothyroidism).
  • Hypercholesterolemia.
  • Depression.
  • Infertility.

Prognosis

  • Generally good with appropriate treatment.
  • Lifelong condition requiring regular follow-up.
  • Potential for normal life expectancy.
  • Need for dose adjustments over time.

Key Points

  • Common condition, especially in women and the elderly.
  • Symptoms can be non-specific and develop slowly.
  • Treatment is effective but requires lifelong adherence.
  • Regular monitoring is essential to ensure optimal management.

References: British Thyroid Foundation, NICE Guidelines (https://www.nice.org.uk/guidance/ng145)

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