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Chapter 23. Function of the Male Reproductive System

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Mr Smith visits his primary care physician complaining of being tired. His BMI is 35 and his blood pressure is 145/90. The physician decides to measure his serum testosterone levels since testosterone levels are reduced with chronic diseases and obesity. Testosterone is produced mainly by the

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A. Leydig cells.

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B. Sertoli cells.

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C. seminiferous tubules.

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D. epididymis.

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E. vas deferens.

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The correct answer is A. Testosterone is produced in Leydig cells. Sertoli cells are required for spermatogenesis and production of ABP and aromatization of estrogens. Seminiferous tubules are where spermatozoa are produced. The epididymis is where sperm is matured. The vas deferens is where sperm are stored and connects the epididymis with ejaculatory duct and the urethra for ejaculation.

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A 46-year-old obese man visits his primary care provider for his yearly checkup. While there, the physician asks about his sex life and mentions that he is having trouble getting and maintaining an erection. What drug will the physician prescribe for the man?

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A. Nitric synthase inhibitors

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B. Tamoxifen

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C. Phosphodiesterase-5 inhibitors

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D. 5-alpha-reductase inhibitors

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The correct answer is C. NO causes erection thus would not give NOS inhibitors. Tamoxifen is a SERM that is given for breast cancer. 5-Alpha-reductase inhibitors prevent conversion of testosterone to 5-alpha-dihydrotestosterone.

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A 45-year-old man is prescribed 5-alpha-reductase inhibitor, finasteride, for benign prostatic hypertrophy. His physician mentions potential side effects of the drug that include

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A. gynecomastia.

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B. increases in prostatic serum antigen (PSA).

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C. eunuchism.

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D. impotence.

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The correct answer is A. Gynecomastia is caused by dihydrotestosterone (DHT). Thus blocking the synthesis of DHT will cause more aromatase activity and increases in estradiol. Estradiol causes increase in breast development, or gynecomastia, in men. DHT or its inhibition has no effect on PSA. Eunuchism is lack of production of all androgens. Reductions in DHT do not cause impotence because there is still testosterone to increase libido and performance.

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A 60-year-old man comes to see his physician for his yearly checkup. His physician measures his serum prostatic antigen levels and finds that they are elevated. What is the potential diagnosis for this man?

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