Benign Prostatic Hyperplasia (BPH) is the non-cancerous enlargement of the prostate gland. This enlargement can lead to bothersome urinary symptoms as the prostate presses on the urethra. To manage these symptoms and reduce prostate size, 5-alpha reductase inhibitors (5-ARIs) are often prescribed. These inhibitors work by targeting specific hormonal pathways within the body to address the underlying cause of prostate growth.
Understanding Benign Prostatic Hyperplasia
The prostate gland is a small organ located below the bladder in men, surrounding the urethra. Its primary function involves producing seminal fluid, which nourishes and transports sperm. As men age, the prostate can begin to grow larger, a condition referred to as benign prostatic hyperplasia. This enlargement is not cancerous, but it can significantly impact urinary function.
When the prostate grows, it can squeeze the urethra, leading to lower urinary tract symptoms. Common symptoms include frequent urination, especially at night, a weak or interrupted urine stream, and a feeling of incomplete bladder emptying. Some individuals may also experience urgency or difficulty starting urination.
How 5-Alpha Reductase Inhibitors Work
Prostate gland growth is influenced by hormones, particularly dihydrotestosterone (DHT). DHT is a potent androgen that stimulates prostate cell growth. It is derived from testosterone through a conversion process catalyzed by the enzyme 5-alpha reductase. This enzyme exists in two main forms: Type 1 and Type 2.
5-alpha reductase inhibitors work by blocking the activity of this enzyme, thereby preventing testosterone from being converted into DHT. By reducing DHT levels within the prostate gland, these medications cause prostate cells to shrink. This reduction in prostate volume helps to relieve pressure on the urethra, leading to improved urinary flow and a decrease in associated symptoms. The different inhibitors may target one or both types of the 5-alpha reductase enzyme, influencing their specific effects.
Common 5-Alpha Reductase Inhibitors
Two primary 5-alpha reductase inhibitors used for BPH treatment are finasteride and dutasteride. Finasteride specifically targets and inhibits the Type 2 form of the 5-alpha reductase enzyme. It is typically administered as a 5 mg oral tablet once daily.
Dutasteride has a broader action, inhibiting both Type 1 and Type 2 forms of the 5-alpha reductase enzyme. This dual inhibition can lead to a more significant reduction in DHT levels. Dutasteride is also typically taken as a 0.5 mg oral capsule once daily.
What to Expect When Taking These Medications
Patients taking 5-alpha reductase inhibitors typically experience a gradual improvement in their urinary symptoms over several months. The medications work by reducing the size of the enlarged prostate gland, which can lead to a stronger urine stream, less frequent urination, and a decrease in nighttime awakenings to urinate. Beyond symptom relief, these inhibitors can also lower the risk of BPH-related complications, such as acute urinary retention and the need for surgery. The full benefits of treatment may not be evident for six to twelve months.
These medications can cause side effects. Common side effects include sexual dysfunction, such as decreased libido, erectile dysfunction, and ejaculatory disorders. Some men may also experience breast tenderness or breast enlargement. It is also important to note that 5-alpha reductase inhibitors can affect prostate-specific antigen (PSA) levels, a blood marker used for prostate cancer screening. These medications typically reduce PSA levels by approximately 50%, so healthcare providers will adjust PSA interpretations accordingly when monitoring for prostate cancer.