Can hypothyroidism cause pleural effusion?

Hypothyroidism Can Cause Pleural Effusion

Yes, hypothyroidism can cause pleural effusion, particularly in cases of severe, long-standing hypothyroidism. While not a common manifestation, pleural effusion can occur alongside other fluid accumulations such as pericardial effusion and ascites in hypothyroid patients.

Pathophysiology and Presentation

• Severe, long-standing hypothyroidism can lead to fluid accumulation in various body cavities, including the pleural space 1
• The mechanism involves increased capillary permeability, extravasation of mucopolysaccharides, and inappropriate antidiuretic hormone secretion 2
• Pleural effusions in hypothyroidism may present alongside other fluid accumulations, particularly pericardial effusion and ascites, a condition sometimes referred to as polyserositis 2

Characteristics of Hypothyroidism-Related Pleural Effusions

• Pleural effusions due to hypothyroidism are often borderline between exudates and transudates 3
• They typically show little evidence of inflammation 3
• In some cases, the effusions can be exudative in nature, as demonstrated in case reports 4
• These effusions may be unilateral or bilateral, and can become massive in severe cases 4, 5

Diagnostic Considerations

• Hypothyroidism should be considered in the differential diagnosis of unexplained pleural effusions, especially when accompanied by other signs of hypothyroidism 1
• Thyroid function tests (TSH, T4) should be performed in patients with unexplained pleural effusions 1
• The diagnosis is often missed because the symptoms develop insidiously and may be nonspecific 2
• Other common causes of pleural effusion should be ruled out, as most effusions in hypothyroid patients are due to other diseases 3

Treatment Approach

• Thyroid hormone replacement therapy is the primary treatment for hypothyroidism-induced pleural effusions 4, 6
• Most pleural effusions resolve with adequate levothyroxine therapy, though this may take several months 6
• In cases of massive effusions causing significant symptoms, drainage procedures may be necessary alongside hormone replacement 4
• Diuretics alone may be insufficient in treating severe exudative effusions associated with hypothyroidism 4

Clinical Pearls and Pitfalls

• The presence of hypothyroidism does not exclude other common causes of pleural effusion, and a thorough evaluation is still warranted 1, 3
• Pleural effusion as an isolated finding in hypothyroidism is rare; it more commonly occurs with other manifestations such as pericardial effusion 3
• Failure to recognize hypothyroidism as a cause of pleural effusion may lead to unnecessary invasive procedures 6
• Monitoring thyroid function is essential in patients receiving medications known to affect thyroid function (e.g., sunitinib), as medication-induced hypothyroidism can also lead to pleural effusions 5

While hypothyroidism is not among the most common causes of pleural effusion, it represents an important and treatable etiology that should be considered in the differential diagnosis of unexplained pleural effusions, particularly when other signs of hypothyroidism are present or when effusions in multiple body cavities are detected.