**Core Concept**
Testosterone replacement therapy (TRT) in hypogonadal males requires careful management to monitor for potential adverse effects, particularly on the prostate gland. Prostate cancer is a significant concern, as testosterone can stimulate cancer growth.

**Why the Correct Answer is Right**
After initiating testosterone replacement therapy, monitoring for prostate cancer is crucial. Prostate-specific antigen (PSA) levels are a sensitive marker for prostate cancer, and elevated levels can indicate cancer presence or recurrence. Regular PSA screening helps identify patients who may require further investigation, such as prostate biopsy. The American Urological Association and the Endocrine Society recommend regular PSA screening in patients initiating TRT.

**Why Each Wrong Option is Incorrect**
**Option B:** Decreasing testosterone levels is the opposite of what occurs with testosterone replacement therapy, which aims to increase circulating testosterone levels to normal or supraphysiological levels.

**Option C:** While testosterone replacement therapy may cause some changes in prostate tissue, it does not specifically decrease the size of benign prostatic tissue lesions. In fact, testosterone can cause an increase in prostate size, which may lead to urinary retention or other complications.

**Option D:** Testosterone replacement therapy can potentially stimulate the growth of prostate cancer cells, not decrease their size. Prostate cancer cells are androgen-dependent, meaning they require testosterone to grow, and TRT can exacerbate this growth.

**Clinical Pearl / High-Yield Fact**
When initiating testosterone replacement therapy, it is essential to discuss the potential risks and benefits with the patient, including the need for regular PSA screening and monitoring for signs of prostate cancer.

**✓ Correct Answer: A. Check PSA levels**