A 47-year-old man presents to his physician because he has noticed that his right breast is noticeably larger than his left breast. Breast examination demonstrates that the right breast is diffusely enlarged. The breast tissue is freely mobile and without distinct masses. The patient repos that the breast has been slowly enlarging over a period of several years. Which of the following is the MOST likely mechanism causing a relative excess of hormone leading to the breast enlargement in this patient?

Peripheral conversion of androgens (testosterone and androstenedione) to estrogens occurs mainly in adipose tissue, muscle, and skin. In patients with chronic liver disease, malnutrition, and hypehyroidism, this peripheral conversion is increased, and may be associated with feminization (seen as changes in hair distribution, body fat distribution, and breast size). Conditions that cause primary or secondary hypogonadism can cause gynecomastia by the mechanisms of decreased production and/or action of testosterone. These conditions can include Klinefelter syndrome, congenital anorchia, testicular trauma or torsion, viral orchitis (e.g., mumps), pituitary tumors, and renal failure. Drugs that can cause gynecomastia by inhibiting testosterone synthesis or action include ketoconazole, metronidazole, cisplatin, spironolactone, and cimetidine. Drugs that can cause gynecomastia because of their estrogen-like activity include diethylstilbestrol, digitalis, and estrogen-containing foods and cosmetics. Ref: Bhasin S., Jameson J.L. (2012). Chapter 346. Disorders of the Testes and Male Reproductive System. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.