Elevated hemoglobin in the absence of polycythemia vera can be due to secondary causes such as chronic hypoxia. Central sleep apnea, often associated with diabetes or neurologic conditions, leads to intermittent hypoxia and compensatory erythropoiesis.

Toronto Notes 2023 – Hematology and Respiratory Medicine, “Polycythemia” Section:

“Secondary erythrocytosis may result from hypoxic conditions including sleep apnea, COPD, or high altitude. Assess for sleep-disordered breathing in patients with elevated hemoglobin and no myeloproliferative features.”

MCCQE1 Objectives (Internal Medicine > 76-7: Hematologic Abnormalities):

“Candidates must investigate secondary causes of elevated hemoglobin, including hypoxia-related conditions.”

Hypertension (A), hypothyroidism (C), and cirrhosis (D) do not cause polycythemia. Alcohol (B) typically causes macrocytosis and anemia.