Hypothyroidism

Epidemiology

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Etiology

  • xxxx

Physiology

  • Myxedema + Obesity: central hypoventilation with respiratory muscle weakness leads to hypoxia and acidosis (with resultant pulmonary vasoconstriction)
  • Ventilatory Drive in Response to Hypoxia and Hypercapnia: decreased (corrects with treatment)

Clinical Manifestations

Endocrinologic Manifestations

Neuro Manifestations

  • Fatigue
  • Hyporeflexia: correlates with propensity for respiratory failure

Pulmonary Manifestations

Pleural Effusion (see Pleural Effusion-Transudate, [[Pleural Effusion-Transudate]] and Pleural Effusion-Exudate, [[Pleural Effusion-Exudate]])

  • Physiology: probably due to transcapillary filtration of liquid and protein
  • Diagnosis
    • Pleural Fluid: transudate, when effusion occurs at the same time as pericardial effusion
      • Isolated pleural effusions can be either transudate or exudate
  • Clinical
    • Most cases of hypothyroidism-associated pleural effusion have a coexistent pericardial effusion (52% with pericardial effusion had a pleural effusion also)

Pulmonary Hypertension (see Pulmonary Hypertension, [[Pulmonary Hypertension]])

  • Epidemiology: both hypothyroidism and hyperthyroidism have been found to be associated with pulmonary hypertension
    • In an echocardiographic study, more than 40% of patients with thyroid diseases had pulmonary hypertension
    • One case of biopsy-proven pulmonary veno-occlusive disease was reported in a patient with Hashimoto thyroiditis
    • Study of adult patients with pulmonary hypertension reported a 49% prevalence of autoimmune thyroid disease (both hypothyroidism and hyperthyroidism): possible common immunogenetic susceptibility
  • Physiology: likely due to hypoventilation (with associated with altered CNS respiratory drive, partial neuropathic component, and partial myopathic components)

Obstructive Sleep Apnea (OSA) (see Obstructive Sleep Apnea, [[Obstructive Sleep Apnea]])

  • OSA (may respond to thyroid hormone replacement alone in some cases): hypothyroidism may induce mucopolysaccharide and protein extravasation in the face, predisposing upper airway obstruction

Acute/Chronic Hypoventilation (see Acute Hypoventilation, [[Acute Hypoventilation]] and Chronic Hypoventilation, [[Chronic Hypoventilation]])

  • Diagnosis
    • ABG: usually normal with hypothyroidism alone
      • Hypothyroidism + Obesity: moderate hypoxemia with hypercapnia
    • PFT’s: usually normal in presence of hypothyroidism alone
      • Hypothyroidism + Obesity: VC, TLC, RV, IC, and ERV may be decreased
      • MIP+MEP: inspiratory and expiratory muscle weakness
  • Clinical: may manifest as failure to wean from ventilator

Cardiac Manifestations

Pericardial Effusion (see Pericardial Effusion, [[Pericardial Effusion]])

  • Epidemiology
  • Diagnosis
    • Pericardiocentesis: protein content ranges from 22-76 g/L
  • Clinical
  • Treatment

Hematologic Manifestations

  • Anemia (see Anemia, [[Anemia]])

Treatment

  • Thyroid Hormone Replacement
    • Pleural effusion resolves with treatment
    • Corrects PFT and ventilation abnormalities
    • Enhances type 2 pneumocyte maturation and surfactant production in “in vitro” and animal studies
    • Intra-amniotic administration decreases incidence of infant respiratory distress syndrome in premature infants

References

  • Pulmonary hypertension and thyroid disease. Chest 2007;132:793–7
  • Pulmonary arterial hypertension and thyroid disease. Chest 2001;119:1980–1
  • Cardiovascular abnormalities in hyperthyroidism: a prospective Doppler echocardiographic study. Am J Med 2005;118:126–31
  • Pulmonary veno-occlusive disease in a patient with a history of Hashimoto’s thyroiditis. Indian J Chest Dis Allied Sci 2005;47:289–92
  • High prevalence of autoimmune thyroid disease in pulmonary arterial hypertension. Chest 2002;122:1668-73