hematology in hyperthyroidism

 Q: Which is more common in hyperthyroidism? (select one) 

A) anemia

B) polycythemia 

Answer: A

Contrary to the expectation, despite an increase in red blood cell mass, patients with hyperthyroidism have normochromic, normocytic anemia. This is due to an increase in plasma volume. Another factor that plays a part is pernicious anemia. 

These patients may also have immune thrombocytopenia (ITP) and antineutrophil antibodies. These patients may also have high serum ferritin. 

Paradoxically, these patients have high prothrombotic factors, which include factors VIII, IX, fibrinogen, von Willebrand factor, and plasminogen activator inhibitor-1. This makes these patients prothrombotic.

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References:

1. Nightingale S, Vitek PJ, Himsworth RL. The haematology of hyperthyroidism. Q J Med 1978; 47:35. 

2. Franchini M, Lippi G, Targher G. Hyperthyroidism and venous thrombosis: a casual or causal association? A systematic literature review. Clin Appl Thromb Hemost 2011; 17:387. 

3. Stuijver DJ, van Zaane B, Romualdi E, et al. The effect of hyperthyroidism on procoagulant, anticoagulant and fibrinolytic factors: a systematic review and meta-analysis. Thromb Haemost 2012; 108:1077.