The endocrine effects of vasectomy: a prospective five-year study

Vasectomy and Prostate Cancer Risk: A 38-Year Nationwide Cohort Study

BACKGROUND

A man's risk of prostate cancer has been linked to his prior reproductive history, with low sperm quality, low ejaculation frequency, and a low number of offspring being associated with increased prostate cancer risk. It is, however, highly controversial whether vasectomy, a common sterilization procedure for men, influences prostate cancer risk.

METHODS

We established a cohort of all Danish men (born between 1937 and 1996) and linked information on vasectomy, doctor visits, socioeconomic factors, and cancer from nationwide registries using unique personal identification numbers. Incidence risk ratios for prostate cancer by time since vasectomy and age at vasectomy during the follow-up were estimated using log-linear Poisson regression.

RESULTS

Overall, 26 238 cases of prostate cancer occurred among 2 150 162 Danish men during 53.4 million person-years of follow-up. Overall, vasectomized men had an increased risk of prostate cancer compared with nonvasectomized men (relative risk = 1.15, 95% confidence interval = 1.10 to 1.20). The increased risk of prostate cancer following vasectomy persisted for at least 30 years after the procedure and was observed regardless of age at vasectomy and cancer stage at diagnosis. Adjustment for the number of visits to the doctor and socioeconomic factors did not explain the association.

CONCLUSIONS

Vasectomy is associated with a statistically significantly increased long-term risk of prostate cancer. The absolute increased risk following vasectomy is nevertheless small, but our finding supports a relationship between reproductive factors and prostate cancer risk.

Reduced sperm yield from testicular biopsies of vasectomized men is due to increased apoptosis

OBJECTIVE

To compare sperm yields, apoptotic indices, and sperm DNA fragmentation from vasectomized men and fertile men undergoing vasectomy.

DESIGN

Testicular biopsies from vasectomized (n = 26) and fertile men (n = 46), were milked to calculate sperm/gram and also formalin-fixed to determine the numbers of developing sperm and incidence and intensities of testicular FasL, Fas, Bax, and Bcl-2. Testicular sperm DNA fragmentation was assessed using the alkaline Comet assay.

SETTING

An ART unit.

PATIENT(S)

Twenty-six men attending for intracytoplasmic sperm injection (ICSI) and 46 men attending for vasectomies.

MAIN OUTCOME MEASURE(S)

Spermatocyte, spermatid and sperm yields, Fas, FasL, and Bax staining.

RESULT(S)

Sperm yields from men vasectomized >5 years previously were markedly reduced compared to fertile men. Increased intensities of FasL and Bax staining were observed in the seminiferous tubules of vasectomy men. FasL positivity (percentage) also increased in Sertoli cells, and both FasL and Fas positivity (percentage) increased in primary spermatocytes and round spermatids of vasectomized men. Sperm DNA fragmentation, an end point marker of apoptosis, increased significantly in vasectomized men compared to fertile men.

CONCLUSION(S)

Reduced sperm yields after vasectomy are associated with increased apoptosis through the Fas-FasL and Bax pathways. Sperm after vasectomy displayed increased DNA fragmentation.

Seminal tissue factor revisited

Studies of seminal tissue factor (TF) are few and mostly based on small numbers. Due to the reported lack of factor (F) X in semen, it has been suggested that TF may not have a role in seminal coagulum formation. However, recent identification of a number of haemostatic factors in semen justifies a re-evaluation of its occurrence. Semen specimens were collected from sub-fertile (n = 19), normally fertile (n = 33), semen donors (n = 30) and vasectomized subjects (n = 62), some fractionated into sperm, a prostasome-rich fraction and seminal plasma. Functional and antigenic TF levels were measured and related to conventional fertility parameters. Semen contains high concentration of functional and antigenic TF. Most TF was found in seminal plasma prepared by low-speed centrifugation. When further fractionated by ultracentrifugation much of this may reside in the pellet (prostasomal fraction). It was also detectable on sperm. TF antigen levels were higher in vasectomized subjects than sub-fertile, normally fertile, donor (p = 0.02) and a 'pooled normal semen parameters' (PNSP) stratification (derived from a combination of measurements) (p = 0.06). The sub-fertile group showed a wider variation than normal, donor or the PNSP subjects. Seminal TF antigen levels correlated significantly with sperm agglutination (p = 0.03) and abnormal sperm morphology (p = 0.04). Subjects with anti-sperm antibodies also showed high TF antigen levels. In conclusion, semen contains functional and antigenic TF at high concentrations. A full complement of clotting factors probably exists in semen, so some pro-coagulant role for TF should not be excluded. Decreased seminal TF levels appear to be associated with seminal parameters that are known to favour male fertility.

The effect of vasectomy on the production of plasma luteinizing hormone and follicle stimulating hormone in man

A prospective study of plasma luteinizing hormone (LH) and follicle stimulating hormone (FSH) in 51 men before vasectomy and 10 days and 3 months after vasectomy revealed a trend to rise in LH 10 days after vasectomy normalizing after 3 months. The literature concerning alterations in LH and FSH after vasectomy is reviewed and different theories are discussed.

Influence of vasectomy on the volume of the non-hyperplastic prostate in men

The influence of vasectomy on the volume of the non-hyperplastic prostate was investigated in 24 men referred consecutively for vasectomy. A comparison of trans-rectal prostatic volume determined ultrasonically before vasectomy and three months post-operatively revealed a highly significant decrease (P less than 0.01) in the volume of the peri-urethral portion of the gland. The volume of the outer zone of the prostate did not change significantly (P greater than 0.1). This may indicate that the prostate is not a functionally homogenous organ. It is postulated that there may be a local influence on the prostate via a hormone transported in the deferent duct and/or the deferential vein.

Effects of long- and short-term vasectomy on structural and functional parameters of the rat

The effects of vasectomy were examined by comparing various parameters from sham operated and vasectomized rats that had undergone surgery at 90 days of age and were killed at 190 or 390 days of age. Significant alterations in the vasectomized rats from sham rats included: testicular and epididymal hypertrophy, formation of pathologic vas deferens granulomas, decreased total serum protein, lowered alpha-globulin levels as shown by serum electrophoresis, and increased sperm agglutinin antibody titers. For vasectomized rats, the differential white blood cell count showed increased numbers of neutrophils and large lymphocytes and decreased numbers of small lymphocytes and basophils. Both the number and extent of many vasectomy-induced alterations were greater in long-term vasectomized than in short-term vasectomized rats.

Endocrine and accessory sex organ function after vasectomy and vasovasostomy

There are no major short- or long-term changes in pituitary testicular axis due to vasectomy. The response of the prostate and epididymis to endogenous may be altered after vasectomy. However, the secretory functions of the two organs return to normal after vasovasostomy. The effects of vasectomy and vasovasostomy on the pituitary gonadal axis and on the accessory sex organs' function are reported.

Vasectomy: five to ten-year follow-up of 200 cases

Five to ten-year follow-up of 200 vasectomies revealed no significant incidence of illnesses or sexual problems.