Infertility (Male)

Male infertility is defined as the inability to achieve a clinical pregnancy after 12 months of regular unprotected sexual intercourse, where a male factor is identified as the primary or contributing cause. It is a major component of reproductive health, contributing to approximately 40–50% of infertility cases in couples — either as an isolated factor or in combination with female factors.

Male infertility is not a single condition but a clinical outcome with multiple underlying causes. These include abnormalities in sperm production, function, or transport, as well as hormonal imbalances, genetic conditions, structural abnormalities, and environmental or lifestyle factors. In a subset of men (approximately 10–15%), no clear cause is identified despite comprehensive evaluation — termed unexplained male infertility.

A structured diagnostic approach — centered on semen analysis, hormonal testing, and targeted imaging or genetic evaluation — allows most causes to be identified and significantly improves the likelihood of successful treatment.

How Conception Normally Occurs

For natural conception to occur, several male reproductive processes must function correctly:

The hypothalamic-pituitary-gonadal (HPG) axis must regulate testosterone production and spermatogenesis
The testes must produce an adequate number of healthy sperm
Sperm must mature and be stored in the epididymis
Sperm must be transported effectively through the vas deferens and ejaculatory ducts
Ejaculation must deliver sperm into the female reproductive tract
Sperm must be capable of motility, capacitation, and fertilization

Male infertility can result from disruption at any of these steps.

Causes of Male Infertility

Sperm production disorders (most common)

Abnormal sperm production is the leading cause of male infertility and may present as:

Oligospermia — low sperm count
Azoospermia — absence of sperm
Asthenozoospermia — reduced sperm motility
Teratozoospermia — abnormal sperm morphology

Underlying causes include:

Testicular dysfunction (primary testicular failure)
Varicocele — dilated scrotal veins impairing testicular temperature regulation
Genetic abnormalities (e.g., Y chromosome microdeletions, Klinefelter syndrome)
Infections affecting the testes (e.g., mumps orchitis)
Exposure to toxins, heat, or radiation

Hormonal (endocrine) causes

Hormonal regulation is essential for spermatogenesis. Disruption of the HPG axis can impair sperm production.

Key causes include:

Hypogonadotropic hypogonadism — insufficient LH/FSH stimulation
Hyperprolactinemia — suppresses GnRH, reducing LH and FSH
Low testosterone — impairs sperm production and libido
Thyroid dysfunction — affects sperm quality and hormonal balance

These causes are particularly important because many are highly treatable.

Obstructive causes (sperm transport issues)

In some men, sperm production is normal, but delivery is impaired.

Common causes:

Congenital absence of the vas deferens (often linked to CFTR mutations)
Ejaculatory duct obstruction
Prior vasectomy
Scarring from infection or surgery

This is a key distinction, as obstructive causes are often correctable or bypassed with assisted reproduction.

Varicocele (up to 30–40% of infertile men)

Varicocele — dilation of the pampiniform venous plexus — is one of the most common and treatable causes of male infertility. It impairs sperm production through:

Increased testicular temperature
Oxidative stress
Reduced oxygenation

Varicocele repair can significantly improve sperm parameters in selected patients.

Lifestyle and environmental factors

Sperm production is highly sensitive to external influences:

Smoking and excessive alcohol use
Obesity and metabolic dysfunction
Heat exposure (saunas, hot tubs, tight clothing)
Environmental toxins (pesticides, heavy metals, endocrine disruptors)
Anabolic steroid use (suppresses endogenous testosterone and spermatogenesis)

These factors are often reversible and represent a major opportunity for intervention.

Unexplained male infertility (10–15%)

In some cases, semen analysis and standard testing appear normal, yet infertility persists. This may reflect:

Sperm DNA fragmentation
Functional defects in fertilization
Subtle hormonal or molecular abnormalities

Advanced testing may reveal these issues, but many remain below current diagnostic thresholds.

The Fertility Investigation — Lab Testing

Semen analysis (foundation of evaluation)

Semen analysis is the primary diagnostic test and assesses:

Parameter	What it assesses	What abnormal results suggest
Sperm concentration	Quantity of sperm	Low count (oligospermia) or azoospermia
Motility	Ability to swim	Reduced fertilization potential
Morphology	Sperm structure	Impaired ability to penetrate egg
Volume	Seminal fluid production	Low volume may indicate obstruction or gland dysfunction

At least two analyses are recommended due to variability.

Hormonal evaluation

Marker	Role in fertility evaluation
FSH	Reflects testicular function; elevated suggests primary testicular failure
LH	Pituitary signaling; helps interpret testosterone status
Total testosterone	Central to spermatogenesis and libido
Prolactin	Elevated levels suppress GnRH and impair fertility
TSH	Thyroid dysfunction impacts sperm quality and hormones
Estradiol	Elevated in obesity; disrupts hormonal balance

Advanced and additional testing

Sperm DNA fragmentation — assesses genetic integrity of sperm
Genetic testing — karyotype, Y chromosome microdeletions, CFTR mutations
Scrotal ultrasound — evaluates varicocele or structural abnormalities
Post-ejaculatory urinalysis — evaluates retrograde ejaculation

Key Endocrine Causes to Identify Early

Hypogonadism

Low testosterone — whether primary (testicular) or secondary (pituitary/hypothalamic) — reduces sperm production. Importantly, exogenous testosterone therapy suppresses spermatogenesis and can worsen infertility.

Hyperprolactinemia

Elevated prolactin suppresses GnRH and reduces LH/FSH secretion. It is a common and highly treatable cause of infertility, with dopamine agonists often restoring normal function.

Thyroid dysfunction

Both hypothyroidism and hyperthyroidism negatively affect sperm quality, libido, and hormonal regulation. Optimization of thyroid function is a key and often overlooked step.

When to Seek Fertility Evaluation

After 12 months of trying without conception
Earlier if:
- Known low testosterone or hormonal disorder
- History of testicular injury, surgery, or undescended testes
- Erectile or ejaculatory dysfunction
- Prior chemotherapy or radiation
- Known genetic condition

Male evaluation should occur in parallel with female evaluation, not sequentially.

Treatment Overview

Treatment is cause-specific and often highly effective.

Lifestyle and medical optimization

Weight loss and metabolic health improvement
Smoking cessation and reduced alcohol intake
Discontinuation of anabolic steroids
Antioxidant therapy in selected cases

Hormonal therapy

Gonadotropins (hCG, FSH) for hypogonadotropic hypogonadism
Dopamine agonists for hyperprolactinemia
Selective estrogen receptor modulators (e.g., clomiphene) to increase endogenous testosterone

Surgical treatment

Varicocele repair
Correction of obstructive lesions
Sperm retrieval procedures (e.g., TESE, micro-TESE)

Assisted reproductive technology (ART)

Intrauterine insemination (IUI) — for mild male factor
In vitro fertilization (IVF) — for moderate impairment
Intracytoplasmic sperm injection (ICSI) — single sperm injected directly into egg; highly effective even in severe male factor infertility

Summary

Male infertility is a common and often under-recognized contributor to reproductive challenges, accounting for up to half of infertility cases. The most common causes include sperm production disorders, hormonal imbalances, varicocele, and lifestyle factors — many of which are identifiable and treatable.

Semen analysis and hormonal testing form the foundation of evaluation, with additional genetic and imaging studies used when indicated. Early and parallel evaluation of both partners is essential.

With accurate diagnosis and targeted treatment — ranging from lifestyle changes to advanced reproductive technologies — the majority of men with infertility can significantly improve their chances of achieving conception.