system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
A 64-year-old man who has not seen a physician in over 20 years presents to your office complaining of recently worsening fatigue and weakness, a decreased appetite, distended abdomen, and easy bruising. His family history is notable for a mother with Hashimoto's thyroiditis, a sister with lupus and a brother with type II diabetes. On further questioning, the patient discloses a history of prior alcoholism as well as intravenous drug use, though he currently only smokes a pack per day of cigarettes. On physical exam, you note the following findings (see Figures A-C) as well as several ecchymoses and telangiectasias. As the patient has not seen a physician in many years, you obtain the following laboratory studies:

Leukocyte count: 4,100/mm^3
Hemoglobin: 9.6 g/dL
Platelet count: 87,000/mm^3
Prothrombin time (PT): 21.0 seconds
International Normalized Ratio (INR): 1.8

Serum:
Creatinine: 1.7 mg/dL
Total bilirubin: 3.2 mg/dL
Aspartate aminotransferase (AST): 225 U/L
Alanine aminotransferase (ALT): 103 U/L
Alkaline phosphatase: 162 U/L
Albumin: 2.6 g/dL
Serum thyroxine (T4): 3.1 µg/dL
Thyroid-stimulating hormone (TSH): 3.4 µU/mL

What is the cause of this patient’s low serum thyroxine?
assistant
Decreased liver synthetic function