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Male infertility

 

Male infertility

Male infertility
Classification and external resources
ICD-10 N46
ICD-9-CM 606
DiseasesDB 7772
MedlinePlus 001191
eMedicine med/3535 med/1167
MeSH D007248

Male infertility refers to a male's inability to cause pregnancy in a fertile female. In humans it accounts for 40-50% of infertility.[1][2][3] It affects approximately 7% of all men.[4] Male infertility is commonly due to deficiencies in the semen, and semen quality is used as a surrogate measure of male fecundity.[5]

Contents

  • Causes 1
    • Pre-testicular causes 1.1
      • Tobacco smoking 1.1.1
      • DNA damage 1.1.2
    • Testicular factors 1.2
    • Post-testicular causes 1.3
  • Diagnosis 2
    • Medical history 2.1
    • Physical examination 2.2
    • Sperm sample 2.3
    • Blood sample 2.4
    • Ultrasonography 2.5
  • Prevention 3
  • Treatment 4
    • Hormonal therapy 4.1
  • Future potential treatments 5
  • See also 6
  • References 7

Causes

Factors relating to male infertility include:[6]

Pre-testicular causes

Pre-testicular factors refer to conditions that impede adequate support of the testes and include situations of poor hormonal support and poor general health including:

Tobacco smoking

Male smokers also have approximately 30% higher odds of infertility.[12] There is increasing evidence that the harmful products of tobacco smoking kill sperm cells.[13][14] Therefore, some governments require manufacturers to put warnings on packets. Smoking tobacco increases intake of cadmium, because the tobacco plant absorbs the metal. Cadmium, being chemically similar to zinc, may replace zinc in the DNA polymerase, which plays a critical role in sperm production. Zinc replaced by cadmium in DNA polymerase can be particularly damaging to the testes.[15]

DNA damage

Common inherited variants in genes that encode enzymes employed in DNA mismatch repair are associated with increased risk of sperm DNA damage and male infertility.[16] As men age there is a consistent decline in semen quality, and this decline appears to be due to DNA damage.[17] (Silva et al., 2012). These findings suggest that DNA damage is an important factor in male infertility.

Testicular factors

Testicular factors refer to conditions where the testes produce semen of low quantity and/or poor quality despite adequate hormonal support and include:

Radiation therapy to a testis decreases its function, but infertility can efficiently be avoided by avoiding radiation to both testes.[23]

Post-testicular causes

Post-testicular factors decrease male fertility due to conditions that affect the male genital system after testicular sperm production and include defects of the genital tract as well as problems in ejaculation:

Diagnosis

The diagnosis of infertility begins with a medical history and physical exam by a physician or nurse practitioner. Typically two separate semen analyses will be required. The provider may order blood tests to look for hormone imbalances, medical conditions, or genetic issues.

Medical history

The history should include prior testicular or penile insults (torsion, cryptorchidism, trauma), infections (mumps orchitis, epididymitis), environmental factors, excessive heat, radiation, medications, and drug use (anabolic steroids, alcohol, smoking).

Sexual habits, frequency and timing of intercourse, use of lubricants, and each partner's previous fertility experiences are important.

Loss of libido and headaches or visual disturbances may indicate a pituitary tumor.

The past medical or surgical history may reveal thyroid or liver disease (abnormalities of spermatogenesis), diabetic neuropathy (retrograde ejaculation), radical pelvic or retroperitoneal surgery (absent seminal emission secondary to sympathetic nerve injury), or hernia repair (damage to the vas deferens or testicular blood supply).

A family history may reveal genetic problems.

Physical examination

Usually, the patient disrobes completely and puts on a gown. The physician or NP will perform a thorough examination of the penis, scrotum, testicles, anus and rectum. An orchidometer can measure testicular volume, which in turn is tightly associated with both sperm and hormonal parameters.[4] A physical exam of the scrotum can reveal a varicocele, but the impact of detecting and surgically correct a varicocele on sperm parameters or overall male fertility is debated.[4]

Sperm sample

The volume of the semen sample, approximate number of total sperm cells, sperm motility/forward progression, and % of sperm with normal morphology are measured. This is the most common type of fertility testing.[24][25] Semen deficiencies are often labeled as follows:

There are various combinations of these as well, e.g. Teratoasthenozoospermia, which is reduced sperm morphology and motility. Low sperm counts are often associated with decreased sperm motility and increased abnormal morphology, thus the terms "oligoasthenoteratozoospermia" or "oligospermia" can be used as a catch-all.

Blood sample

Common hormonal test include determination of FSH and testosterone levels. A blood sample can reveal genetic causes of infertility, e.g. Klinefelter syndrome, a Y chromosome microdeletion, or cystic fibrosis.

Ultrasonography

Ultrasonography of the scrotum is useful when there is a suspicion of some particular diseases. It may detect signs of testicular dysgenesis, which is often related to an impaired spermatogenesis and to a higher risk of testicular cancer.[4] Scrotum ultrasonography may also detect testicular lesions suggestive of malignancy. A decreased testicular vascularization is characteristic of testicular torsion, whereas hyperemia is often observed in epididymo-orchitis or in some malignant conditions such as lymphoma and leukemia.[4] Doppler ultrasonography useful in assessing venous reflux in case of a varicocele, when palpation is unreliable or in detecting recurrence or persistence after surgery, although the impact of its detection and surgical correction on sperm parameters and overall fertility is debated.[4]

Dilation of the head or tail of the epididymis is suggestive of obstruction or inflammation of the male reproductive tract.[4] Such abnormalities are associated with abnormalities in sperm parameters, as are abnormalities in the texture of the epididymis.[4] Scrotal and transrectal ultrasonography (TRUS) are useful in detecting uni- or bilateral congenital absence of the vas deferens (CBAVD), which may be associated with abnormalities or agenesis of the epididymis, seminal vesicles or kidneys, and indicate the need for testicular sperm extraction.[4] TRUS plays a key role in assessing azoospermia caused by obstruction, and detecting distal CBAVD or anomalies related to obstruction of the ejaculatory duct, such as abnormalities within the duct itself, a median cyst of the prostate (indicating a need for cyst aspiration), or an impairment of the seminal vesicles to become enlarged or emptied.[4]

Prevention

Some strategies suggested or proposed for avoiding male infertility include the following:

Treatment

Treatments vary according to the underlying disease and the degree of the impairment of the male fertility. Further, in an infertility situation, the fertility of the female needs to be considered.

Pre-testicular conditions can often be addressed by medical means or interventions.

Testicular-based male infertility tends to be resistant to medication. Usual approaches include using the sperm for intrauterine insemination (IUI), in vitro fertilization (IVF), or IVF with intracytoplasmatic sperm injection (ICSI). With IVF-ICSI even with a few sperm pregnancies can be achieved.

Obstructive causes of post-testicular infertility can be overcome with either surgery or IVF-ICSI. Ejaculatory factors may be treatable by medication, or by IUI therapy or IVF.

Vitamin E helps counter oxidative stress,[28] which is associated with sperm DNA damage and reduced sperm motility.[29] A hormone-antioxidant combination may improve sperm count and motility.[30] Oral antioxidants given to males in couples undergoing in vitro fertilisation for male factor or unexplained subfertility result in significantly higher live birth rate.[31]

Hormonal therapy

Administration of luteinizing hormone (LH) (or human chorionic gonadotropin) and follicle-stimulating hormone (FSH) is very effective in the treatment of male infertility due to hypogonadotropic hypogonadism.[32] Although controversial,[33] off-label clomiphene citrate, an antiestrogen, may also be effective by elevating gonadotropin levels.[32]

Though androgens are absolutely essential for spermatogenesis and therefore male fertility, exogenous testosterone therapy has been found to be ineffective in benefiting men with low sperm count.[34] This is thought to be because very high local levels of testosterone in the testes (concentrations in the seminiferous tubules are 20- to 100-fold greater than circulating levels)[35] are required to mediate spermatogenesis, and exogenous testosterone therapy (which is administered systemically) cannot achieve these required high local concentrations (at least not without extremely supraphysiological dosages).[34] Moreover, exogenous androgen therapy can actually impair or abolish male fertility by suppressing gonadotropin secretion from the pituitary gland, as seen in users of androgens/anabolic steroids (who often have partially or completely suppressed sperm production).[32][34] This is because suppression of gonadotropin levels results in decreased testicular androgen production (causing diminished local concentrations in the testes)[32][34] and because FSH is independently critical for spermatogenesis.[36][37] In contrast to FSH, LH has little role in male fertility outside of inducing gonadal testosterone production.[38]

Estrogen, at some concentration, has been found to be essential for male fertility/spermatogenesis.[39][40] However, estrogen levels that are too high can impair male fertility by suppressing gonadotropin secretion and thereby diminishing intratesticular androgen levels.[34] As such, clomiphene citrate (an antiestrogen) and aromatase inhibitors such as testolactone or anastrozole have shown effectiveness in benefiting spermatogenesis.[34]

Low-dose estrogen and testosterone combination therapy may improve sperm count and motility in some men,[41] including in men with severe oligospermia.[42][43]

Future potential treatments

Researchers at Münster University developed in vitro culture conditions using a three-dimensional agar culture system which induces mouse testicular germ cells to reach the final stages of spermatogenesis, including spermatozoa generation.[44] If reproduced in humans, this could potentially enable infertile men to father children with their own sperm.[45][46]
Researchers from Montana State University developed precursor of sperm from skin of infertile men. It is a ray of hope in real mean for future treatment of infertility in men.[47]

See also

References

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  16. ^ Ji G, Long Y, Zhou Y, Huang C, Gu A, Wang X (2012). Common variants in mismatch repair genes associated with increased risk of sperm DNA damage and male infertility. BMC Med 10:49. doi: 10.1186/1741-7015-10-49. PMID 22594646
  17. ^ Silva LF, Oliveira JB, Petersen CG, Mauri AL, Massaro FC, Cavagna M, Baruffi RL, Franco JG Jr (2012). The effects of male age on sperm analysis by motile sperm organelle morphology examination (MSOME). Reprod Biol Endocrinol 10:19. doi: 10.1186/1477-7827-10-19. PMID 22429861
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