Letrozole in Patients With Hepatopulmonary Syndrome

Inclusion Criteria * Diagnosis of moderate to very severe hepatopulmonary syndrome which consists of having all 3 of the following conditions: * Presence of liver disease or portal hypertension * Intrapulmonary shunting on contrast-enhanced echocardiogram * Hypoxemia \[A-a gradient ≥15mmHg (or ≥20mmHg if age \>64) and PaO2\<80mmHg on arterial blood gas testing\] * Child-Pugh class A or B liver disease * MELD score \< 20 * ≥ 18 years old * Female subjects must be post-menopausal (defined as 12 months of spontaneous amenorrhea or 6 weeks postsurgical bilateral oophorectomy without or without hysterectomy) * Ability to provide informed consent Exclusion Criteria * Enrollment in a clinical trial or concurrent use of another investigational drug or device therapy (i.e., outside of study treatment) during, or within 28 days of baseline * Current hepatic encephalopathy * Expectation of liver transplant within six months of randomization * Concomitant lung disease defined as restriction (TLC \< 70%) or obstruction (FEV1 \< 80% \& FEV1/FVC \< 70%) * Inability to comply with the study protocol * Osteoporosis * Premenopausal women (those who have not reached 1 year absence of menarche) * Vulnerable study population, including imprisoned individuals, or those who cannot consent on their own.