Throw us a bone

by Anthony Balchunas, MS, PA-C

Benign Prostate Hyperplasia (better known as BPH or enlarged prostate) is one of the most common health problems encountered in aging men. By age 40, approximately 8% of men have evidence of prostate (not prostrate) enlargement when tissue samples of the prostate gland are examined under the microscope. The incidence of BPH increases to 50% in men greater than 50 years of age and is as high as 90% in men greater than 80 years of age.¹

BPH can cause a broad spectrum of bothersome clinical symptoms ranging from mild slowing of the urinary stream (hesitancy) to painful retention resulting from the bladder's inability to release stored urine. When inability to empty the bladder becomes an ongoing problem, more serious health consequences may follow. Involuntary leakage of urine (incontinence), urinary tract infection, and deterioration in kidney function are examples of these more serious consequences of prostate enlargement. Scientific studies have also shown a clear relationship between symptoms associated with prostate enlargement and male sexual dysfunction. ²

Because BPH is a disorder that is found more commonly in elderly men, it is becoming a more significant public health problem as the male population ages. According to the Urologic Diseases in America project by Wei³ , approximately 4.5 million visits were made to medical offices in 2000 for the primary diagnosis of BPH, and nearly 8 million visits were made for either a primary or secondary diagnosis of BPH. In the same year the direct cost of treating BPH (not including the cost of outpatient medications) was estimated to be $1.1 billion. When considering the financial and social impact of BPH, it is important to understand that the population in America is rapidly changing. According to US Census Bureau projections, the elderly population will more than double between 2000 and 2030, growing from 35 million to over 70 million.
Much of this growth is attributed to members of the "baby boom" generation who will enter their elderly years between 2010 and 2030. The "oldest old", those aged 85 and over, are the most rapidly growing elderly age group. The oldest old represented 12.1% of the elderly population in 2000 and 1.5% of the total population. In 2050, they are projected to be 24% of elderly Americans and 5% of all Americans.⁴ When one considers the fact that BPH is a disorder of aging, it becomes evident that the diagnosis and management of this common clinical disorder is destined to become a real public health issue.

Anatomy of the Prostate

The prostate is a gland (an organ that secretes fluid) which is an important part of both the urinary and reproductive organ systems. The prostate (from the Greek word prostates, literally "protector" or "guardian") is shaped like a walnut and is located between the opening of the bladder (the bladder neck) and the portion of the urethra (the tube that drains urine from the bladder) that travels through the penis. In front of the prostate gland lies the pubic bone and the rectum is located directly behind. Prior to developing any significant enlargement, the prostate weighs about 15 to 20 grams and is roughly 3 to 4 cm in length. It can be roughly divided into three lobes or sections—two lateral lobes and one median lobe. There are four distinct regions within the prostate gland (often referred to as zones); anterior, central, peripheral, and transition. In a young man the peripheral zone of the prostate, which is found along the back margin of the gland closest to the rectum, makes up approximately 80% of the total prostate volume. As men age the relative size of the peripheral zone remains stable while the two zones closest to the urethra- the central and transition begin to enlarge. By the time significant prostate enlargement occurs, the transition zone can occupy as much as 50% to 80% of the total prostate volume.

Inside the prostate one can find a mixture of glands (which produce prostatic fluid) and tissue called stroma (which contains muscle cells, connective tissue, nerves, and blood vessels). Some of the prostate's muscle cells merge with the muscle cells at the base of the bladder and form what is known as the internal sphincter. This circular band of muscle wraps around the urethra and reflexively contracts to keep the urethra closed, thus preventing leakage of urine. Around the outside of the prostate is a thick fibrous capsule which is relatively inelastic. Along the surface of this capsule run the nerves and blood vessels that play an important part in the control of erectile function. Attached to the back of the prostate are a paired sets of seminal vesicles— the organs that produce semen. Upon ejaculation, semen is carried through the tissue of the prostate by the paired ejaculatory ducts and is deposited in the urethra. There it mixes with prostatic fluid and is expelled forcefully out through the urethra by the rhythmic contraction of the prostate and the pelvic floor muscles. Because the prostate gland produces approximately one third of the total volume of fluid released during ejaculation, it can be considered an important part of the reproductive system in men. Similarly, its role in the control of urinary function and prevention of urine leakage makes it an important part of the Genito-Urinary or GU system.

Basic Function (Physiology) of The Prostate

The smooth muscle contained within the prostate plays a vital role in the prevention of involuntary loss of urine (urinary incontinence). As urine drains from the kidneys into the bladder, the volume of the bladder increases resulting in increased tension placed on its walls (think about a balloon being inflated with air). The smooth muscle at the base of the bladder will reflexively tighten to provide increased tension at the neck of the bladder thus preventing leakage. When pressure within the abdomen increases—such as with coughing, sneezing, or laughing, the pressure within the bladder increases as well. The smooth muscle of the prostate which makes up part of the internal sphincter will reflexively contract with increased abdominal pressure to prevent leakage of urine. The same fibers will also contract when a man ejaculates, thus preventing backward flow of semen into the bladder.

Any insult to the smooth muscle of the prostate (such as side effects from drugs or prostate surgery) can result in the expulsion of sperm into the bladder rather than out the urethra at the time of ejaculation. This condition is commonly referred to as retrograde ejaculation. It can also result from damage to the nerves that innervate the prostate—a common occurrence in pelvic surgery and spinal cord injury.

The prostate also plays a vital role in normal functioning of the male reproductive system. Prostate fluid is excreted along with sperm and seminal fluid when a man ejaculates. The pH of the prostatic fluid is slightly alkaline and this helps to neutralize the hostile acidic environment within the vagina. Prostatic fluid also contains zinc which helps to stabilize the small packet of DNA (genetic material) contained within each individual sperm. Zinc deficiency in men has been shown to be linked with lower fertility because of increased sperm fragility.⁵ Other constituents from the prostate such as acid phosphatase, citric acid, fibrinolysin, prostate specific antigen, and proteolytic enzymes help to support optimal sperm function while reducing the damaging effects of the vaginal environment. One of the constituents of prostate secretions—prostate specific antigen (PSA) is a proteolytic enzyme that helps to break down the ejaculate allowing the sperm to freely swim toward the ovum (egg). PSA is predictably released from the prostate gland into the surrounding blood and thus can be measured when a peripheral blood sample is taken. When followed at periodic intervals, measurement of serum PSA may help identify individuals at risk for accelerated prostate enlargement and prostate cancer.

Regulation of prostate growth and function is predominantly controlled by the hormone testosterone and its more potent derivative—dihydrotestosterone (DHT). The fascinating discovery of this relationship dates back to 1786 when a Scotsman, John Hunter (known as the "Father of Scientific Surgery"), described his observations regarding the effect of castration on the prostate gland of bulls: "The prostate gland and the glans along the urethra in the perfect male are large and pulpy".........."while in the castrated animal they are small, flabby, tough and ligamentous, and have little secretion." These observations where later noted in a group of 26 Chinese eunuchs serving the last emperor of the Qing Dynasty. In 1960 these individuals became the subject of detailed medical examinations which included digital examination of the prostate gland.

In almost all of the men no prostate tissue was identifiable. Based on these reports and the few published studies of autopsy performed on men with congenital testosterone deficiency, it became evident that hormones secreted from the testicles where essential for the development and preservation of the prostate. Later on, the specific role of testosterone and its derivative dihydrotestosterone was clarified by Jean Wilson and colleagues at the University of Texas in Dallas.⁶ This important work paved the way for a better understanding on how a certain class of medications, 5 alpha-reductase inhibitors, may be effectively used to treat and prevent symptomatic BPH.

References:

1. Barry MJ: Epidemiology and natural history of benign prostatic hyperplasia. Urol Clin North Am 1990;17:495-507.
2. Rosen R. Multinational Survey of the Aging Male (MSAM-7). Presented at the Annual Meeting of the American Urological Association; May 26, 2002; Orlando, Fla.
3. Wei JT, et al: Urologic diseases in America project. J Urology 2005;173:1256-1261.
4. U.S. Census Bureau, "65+ in the United States: 2005," December 2005; U.S. Census Bureau, U.S. Interim Projections by Age, Sex, Race, and Hispanic Origin, 2004.
5. Nutr Res. 2009 Feb;29(2):82-8.
6. Wison JD, Walker JD. The conversion of testosterone to dihydrotestosterone by skin slices of man. J Clin Invest. 1969;48:371-379.

This article has been reviewed by a member of the Wellness Partners Editorial Board.

Posted May 2011