Asthenozoospermia Overview

Introduction

Asthenozoospermia is defined as reduced or absent sperm motility (< 32%) in fresh ejaculate. It is one of the main causes of male infertility and can occur in isolation or, as in the majority of cases, together with oligozoospermia (low sperm concentration) and teratozoospermia (abnormal sperm morphology).

Men with asthenozoospermia are also 10 times more likely to have elevated sperm DNA damage which impairs fertilization and development of the embryo.
_{Source: Gill K, et al. (2023)}

Biologically asthenozoopsermia is associated with structural defects of the sperm tail (flagellum). The sperm tail is composed of a core axoneme (axial filament) and near axoneme structures surrounded by mitochondrial and fibrous sheaths.

Interestingly the sperm core ‘axoneme’ and ‘cilia’ of other cell types within the body, share similarities in their ultrastructure, that cases of asthenozoopsermia can occur in males diagnosed with primary ciliary dyskinesia or Kartagener’s syndrome.

Fortunately, the majority of asthenozoospermia cases is due to common causes of infertility and is clearly visible during semen analysis with absent, short, angulated or irregular tails on spermatozoa.

Progesterone receptors found on the outer membrane of sperm mitochondria reveals how female progesterone levels can increase sperm ATP production and improve sperm motility.

Symptoms of Asthenozoospermia

The symptoms of low sperm motility are similar to men diagnosed with oligospermia or azoospermia. The primary symptom is the inability to conceive a child despite 1 year of frequent and unprotected intercourse.

Other symptoms may include:

• Erectile dysfunction or low sex drive
• Pain or swelling in testicles
• Changes in body hair indicating hormonal abnormality

Risks associated with Asthenozoospermia

Men suffering from abnormal sperm parameters are susceptible to further issues such as:

• Stress, loss of self-esteem and relationship issues due to difficulties trying to conceive
• Increased risk of cancer

Causes of Asthenozoospermia

The causes of low sperm motility fall into 3 main categories:

• Medical
• Environmental
• Lifestyle

Diagnosis of Asthenozoospermia

The inability to conceive despite 1 year of frequent and unprotected intercourse is defined as infertility in a couple. At this stage, it is advised that both partners consult a doctor since the inability to conceive frequently occurs due to a combination of issues from both partners rather than one.

For males partners at this initial consultation, the European Academy of Andrology recommends doctors perform the following:

• General physical examination to assess any sign of hypogonadism.
• Physical examination of the scrotum to assess; the volume and consistency of the testicles and epididymis, the total or partial absence of deferent ducts, the presence of varicoceles.
• Two semen analyses (3 months apart) according to the WHO guidelines.

Semen samples can be collected in the clinic or at home following 2 to 7 days of sexual abstinence. If collected at home, the sample should immediately be transported at room temperature to the nearest laboratory, since sperm motility needs to be assessed within 30 minutes of semen liquefaction for accurate results.

However a second semen test 3 months later is necessary to correctly diagnose asthenospermia. Males with borderline results should request a third semen analyses to potentially avoid unnecessary treatment.

When analysing the results, doctors place a greater importance on progressive motility than total motility. Progressive motility is essential for natural conception, since sperm need to swim against the flow of secretions within the fallopian tubes to reach the oocyte (unfertilised egg).

For this reason, some diagnoses of asthenospermia nowadays also includes a detailed breakdown of sperm motility according to the grades (A, B, C, D) and the quantity (%) of each observed in the semen sample.
_{Source: Vasan S S, (2011)}

Grade	Type of sperm motility
A	Rapid progressive motility (>25 μm/s at 37°C and >20 μm/s at 20°C; Note: 25 μm is approximately equal to 5 head lengths or half a tail length).
B	Sluggish or slow forward progression
C	Nonprogressive motility (<5 μm/s)
D	No motility

Using this grading system, semen samples classified as asthenospermia may sometimes be considered ‘normal’ if at least 50% of the spermatozoa are of grade A and B. Conversely, if more than 50% of sperm are immotile, semen samples must be checked for viability to exclude a rare condition known as necrozoospermia.

It is also important that spontaneous asthenospermia, which can be caused by exposure of sperm cells to rubber (condoms), spermicides, extreme temperatures or long delays between collection and examination, is excluded during preliminary investigations before a definitive (final) diagnosis of asthenospermia.

After semen analyses, the doctor may recommend further tests to determine or rule out potential causes of asthenospermia.

These tests include:

• Scrotal ultrasound to look at the testicles and surrounding tissues.
• Blood tests to:
  i) Check the hormones secreted by the testicles and pituitary gland.
  ii) Perform karyotyping (genetic tests).
• Other less commonly used tests:
  i) Biopsy of the testicles to determine if there is normal production of sperm.
  ii) Anti-sperm antibody tests to check if the immune system is attacking the sperm cells.
  iii) Specialized sperm function tests to determine the penetration strength or attaching potential of the sperm cells.

Although sperm motility and DNA fragmentation are intrinsically linked. Zhang et al. demonstrated that removing sperm with abnormal motility (<25 μm/s) almost halved the level of DNA fragmentation found in raw semen samples.

Treatment of Asthenozoospermia

Treating asthenozoospermia is a step-by-step process. The first step towards treatment is diagnosing and understanding the exact cause of asthenozoospermia in your individual case.

Once a diagnosis has been made, your Doctor will recommend one (or a combination) of the following treatment options for asthenozoospermia:

• Lifestyle
• Supplements
• Environment
• Surgery
• Medication
• Assisted Reproductive Technology

Fortunately, this does not mean your ability to successfully fertilize the embryo is nill, however the odds of successful fertilization, clinical pregnancy and live birth is significantly reduced.