ABIM Exam Disease of the Week Profile: Benign Prostatic Hyperplasia
This week’s important concept to understand for the Internal Medicine Board (ABIM) exam is Benign Prostatic Hyperplasia.
INTRODUCTION Benign prostatic hyperplasia (BPH) is a common condition among males as they advance in age. It involves hyperplasia of prostatic stromal and epithelial cells that leads to the formation of a nodule in the region of the periurethral region of the prostate. These nodules can compress the urethral canal, which can lead to partial or complete obstruction of urine flow.
PATHOPHYSIOLOGY/ETIOLOGY Androgens play a permissive role in the development of BPH. This means that androgens need to be present for BPH to occur but do not necessarily directly cause the condition. Testosterone is converted to dihydrotestosterone (DHT) by the enzyme 5-alpha reductase. DHT is a metabolite of testosterone and is considered a critical mediator of prostatic growth. 5-alpha reductase is primarily concentrated in the prostatic stromal cells; therefore, this is the site for the majority of synthesis of DHT. Understanding the role of 5-alpha reductase and the production of DHT is essential as inhibiting this enzyme plays a major role in the management of BPH (discussed in the Management section).
Anatomically, the posterior urethral glands and transitional zone of the prostate are the sites where hyperplasia most often occurs. Less often, BPH occurs in the peripheral zone of the prostate. The peripheral zone is the location that is most notorious for prostate cancer; therefore, any nodules that are found in the peripheral zone are biopsied to rule out prostate cancer. Individuals who have BPH are NOT at increased risk to develop prostate cancer.
DIAGNOSIS Two definitive tests must be done to establish that an individual has BPH. A digital rectal examination is performed in males who are 50 years of age or older. In African American males, a digital rectal exam may be performed at 40 years of age as African Americans are at an increased risk of developing BPH or prostate cancer. A digital rectal exam will assess for any enlargement or irregularity of the prostate gland.
The second diagnostic test is a urinalysis. This is done to see if patient has any pyuria (white blood cells in the urine) or hematuria. Checking PSA levels is controversial because as the prostate size increases, so does the PSA level. Using PSA as a screening test for prostate cancer will produce many false positive results in individuals who have BPH and is therefore not established as a universal recommended screening test.
SYMPTOMS The main symptoms of BPH include: Decreased urinary stream Urinary retention Increased frequency of urine Increased urgency Recurrent urinary tract infections in males Dysuria Nocturia Post-urination dribbling Abdominal straining to initiate urinary stream
MANAGEMENT The management of BPH can be broken down into lifestyle modifications, pharmacological management, and surgical intervention.
Lifestyle modifications include decreasing fluid intake before bedtime, decreasing alcohol consumption and caffeine intake, and follow timed voiding schedules.
Pharmacological management of BPH includes two classes of medications: alpha antagonists (a.k.a alpha blockers) and 5-alpha reductase inhibitors.
Alpha antagonists relax the prostatic smooth muscle in the bladder outflow tract. These medications are considered first line treatment for BPH as they are effective in about 70 percent of men and respond within 48 hours of initiating treatment. Some examples of alpha antagonists include: terazosin, doxazosin, tamsulosin, alfuzosin, and silodosin. Prazosin is an example of an alpha antagonist that is not used in the management of BPH as it requires frequent dosing and has more side effects.
The most common side effect of alpha antagonists is postural hypotension, which can lead to dizziness and headaches. Alpha antagonists should be avoided with agents used for erectile dysfunction (eg. Sildenafil) as concurrent use can exacerbate postural hypotension. Another potential side effect of alpha antagonists is abnormal ejaculation.
The second pharmacological agent class that is used in the management of BPH is 5-alpha reductase inhibitors. These agents take about 6 months to show their full efficacy as they decrease the prostate size and relieve urinary symptoms. They tend to arrest the growth of prostate cells as they inhibit the production of dihydrotestosterone (DHT), which as mentioned above, plays a major role in the development of BPH. 5-alpha reductase inhibitors also decrease serum PSA levels. Examples of 5-alpha reductase inhibitors include finasteride and dutasteride.
The main side effects of these agents are erectile and ejaculatory dysfunction, decreased libido, gynecomastia, and breast tenderness.
When lifestyle modifications and use of pharmacological agents do not relieve symptoms of BPH, surgical intervention is a viable treatment option. The surgical options for BPH include either transurethral resection of the prostate (TURP) or transurethral microwave thermotherapy. Both are similarly efficacious in the treatment of BPH.
Remember that prostate disorders are listed as one of the medical content categories in the ABIM blueprint for the Internal Medicine board exam.
You can see all the previous ABIM Exam disease of the week blog posts at the Knowmedge Blog. You can find also additional topics and questions directly from the Knowmedge Internal Medicine ABIM Board Exam Review Questions QVault.