Pathophysiology
Summary
Benign prostatic hyperplasia (BPH) is an exceedingly common condition in older men, characterized by the enlargement of the prostate due to the hyperplasia of cells in the transitional zone of the prostate. This zone includes the middle and lateral lobes which surround the urethra, and its enlargement consequently causes urinary obstruction. The enzyme 5-alpha reductase plays a pivotal role by converting testosterone to the more potent dihydrotestosterone (DHT), leading to prostatic epithelial and stromal hyperplasia and thus, prostate enlargement.
Clinically, BPH often results in hesitancy, weak urinary stream, urgency, increased frequency of micturition, & nocturia. Ureteral obstruction due to BPH can cause urinary retention & bladder distention. Chronic obstruction from BPH can lead to complications like recurrent UTIs, bilateral ureteral dilation & hydronephrosis, acute kidney injury (AKI) and even renal failure. On digital rectal exam, BPH typically shows a smooth, symmetric enlargement, in contrast to malignancy which presents with asymmetry or nodularity. Therapeutic options include alpha-1 antagonists like terazosin, which relax the smooth muscle surrounding the prostatic urethra, and 5-alpha reductase inhibitors like finasteride and dutasteride, which decrease prostate volume by inhibiting the conversion of testosterone to DHT.
In contrast, prostate adenocarcinoma is the most common malignancy and the second leading cause of cancer death in males. Risk factors include family history, African American descent, and smoking. Unlike BPH, prostate cancer is usually asymptomatic and tends to develop in the peripheral zone of the prostate, particularly the posterior lobe. Consequently, it rarely causes urinary symptoms. Prostate cancer is distinguishable from BPH on digital rectal exam by its asymmetric enlargement, nodule formation, & areas of induration. It forms osteoblastic metastases as opposed to osteoclastic, and has a propensity for early metastasis—often to the vertebral column, resulting in back pain.
Prostate-specific antigen (PSA) is used to monitor for recurrence in men with a history of prostate cancer. Histologically, prostate cancer shows well-defined glands with cells featuring dark cytoplasm & large nuclei. Pharmacologic management includes continuous GnRH agonists like leuprolide, which decrease androgen levels, thereby inhibiting the growth of the androgen-dependent prostate cancer cells.
Lesson Outline
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FAQs
BPH primarily originates from hyperplasia of cells in the transitional zone of the prostate, which is the innermost layer surrounding the urethra. The enzyme 5-alpha reductase converts testosterone into a more potent form called dihydrotestosterone (DHT). DHT then stimulates the prostate cells to multiply, leading to an increase in both glandular epithelial and smooth muscle cells. This hyperplasia results in the enlargement of the prostate.
Due to the enlargement of the prostate, BPH often leads to urinary symptoms. These include hesitancy in initiating urination, a weak urinary stream, and a sense of urgency to urinate. Additionally, patients may experience increased frequency of urination and nocturia, which is waking up to urinate during the night. If left untreated, BPH can cause more severe complications such as urinary retention, bladder distention, and even renal failure.
A digital rectal exam is often the first step in diagnosing BPH. During this exam, a smooth, symmetric enlargement of the prostate is usually observed, without the presence of nodules or tenderness. These physical findings, along with the patient's reported urinary symptoms, help in diagnosing BPH. It's important to differentiate BPH from prostate cancer, which may present with asymmetrical enlargement or nodules on the prostate.
For BPH, medications such as alpha-1 antagonists and 5-alpha reductase inhibitors are commonly used. Alpha-1 antagonists like terazosin relax the smooth muscle surrounding the prostatic urethra, improving urine flow. 5-alpha reductase inhibitors like finasteride and dutasteride reduce the size of the prostate by inhibiting the conversion of testosterone to DHT. Prostate cancer, on the other hand, is often treated with continuous administration of GnRH agonists like leuprolide, which decrease androgen levels and inhibit the growth of the cancer.
Prostate adenocarcinoma is the most common type of malignancy in males and the second leading cause of cancer-related deaths. It is often asymptomatic in its early stages due to its development in the peripheral zone of the prostate. Risk factors include a family history of prostate cancer, smoking, and being of African American descent. Monitoring for recurrence in men with a history of prostate cancer is often done using prostate-specific antigen (PSA) levels, although its use for screening is controversial.
