Male Fertility: Production, Pathology & Laboratory Evaluation

Site of production: seminiferous tubules (testes)
- During spermatogenesis histones are replaced by protamines → first wave of nuclear chromatin compaction.
Post-testicular maturation: epididymal transit
- Path: caput (upper) → corpus (central) → cauda (lower, storage until ejaculation)
- Additional chromatin compaction & acquisition of progressive motility.
Total time for one cycle of spermatogenesis ≈ 74 days (continuous, lifelong).

Three anatomical levels
- Pre-testicular (endocrine/hypothalamic-pituitary)
- Testicular (intrinsic to the gonad)
- Post-testicular (ductal transport & maturation)
Temporal origin
- Congenital (present from birth)
- Acquired (develop later)
Terminology
- Idiopathic male infertility: abnormal semen parameters but no identifiable aetiology.
- Unexplained male infertility: normal semen parameters & no male/female cause found.

Key hormones: FSH, LH ("gonadotropins")
- Reduced FSH/LH → hypogonadotropic hypogonadism.
  • Congenital example: Kallmann ("Pullman") syndrome.
  • Acquired: malnutrition, excessive exercise, systemic illness suppress GnRH pulsatility.
Consequence: ↓ intratesticular testosterone & impaired spermatogenesis.

Chromosomal
- Klinefelter syndrome (XXY): subtle phenotype, frequently diagnosed during infertility work-up.
- Y-chromosome microdeletions (AZF regions) → severe oligozoospermia/azoospermia; often sole symptom is infertility.
Acquired gonadal injury
- Trauma, orchitis, torsion, testicular cancer.
- Varicocele (pampiniform venous plexus dilation): common in fertile men but over-represented in infertile cohort; may increase scrotal temperature.
- Infections/inflammation.

Congenital bilateral absence of vas deferens (CBAVD) – often CFTR-related.
Obstructive pathologies (epididymis, vas, ejaculatory ducts).
Systemic disease or epididymal inflammation during storage phase (DNA damage hotspot).
Lifestyle / environmental influences on maturing or ejaculated sperm
- Smoking, alcohol, recreational drugs, toxins.
- Medications: certain antibiotics, NSAIDs, antidepressants, chemotherapy, radiation.
- Heat (sauna, laptops), obesity, advanced paternal age (quality starts to decline ≈ 40–45 y, gradual).

Laboratory steps
- Macroscopy: volume, viscosity, pH.
- Microscopy: concentration & motility counted on haemocytometer; morphology on stained smear.
Counting example
- Count ext{\le}200 sperm across 10 haemocytometer rows → derive concentration (million ml⁻¹).

Semen volume < 1.4 ml → hypospermia.
Sperm concentration < 16 million ml⁻¹ OR total count < 39 million → oligozoospermia (none = azoospermia).
Progressive motility < 30\% → asthenozoospermia.
Normal morphology < 4\% → teratozoospermia.
Combination: Oligo-Astheno-Terato-zoospermia (OAT).
If all parameters ≥ limits → normozoospermia.

Limits describe the sample, not the patient or aetiology.
Natural intra-individual variability; illness or abstinence interval can transiently lower quality.
Inter / intra-observer variation in manual counts.
\approx15\% of infertile men show normal semen analysis (limitation in sensitivity).
Semen analysis does NOT assess
- Capacitation capability, acrosome reaction, zona binding.
- Genomic integrity (DNA fragmentation).

Definition: single or double-strand DNA breaks in sperm nucleus.
Timing
- During testicular spermatogenesis.
- Predominantly during epididymal maturation/storage (most vulnerable phase).
- Post-ejaculation (cryopreservation, prolonged in vitro incubation).
Mechanism: Oxidative stress
- Reactive Oxygen Species (ROS) generated by metabolically active sperm, leukocytes, immature cells with residual cytoplasm.
- Antioxidants in epididymal fluid & seminal plasma buffer ROS; imbalance → lipid peroxidation (affects motility) & DNA breaks.

TUNEL assay (Concept Fertility standard)
- Brown nuclei = fragmented; blue = intact → calculate % SDF.
Alternatives: SCSA, HALO, COMET; lack direct comparability (e.g., 20\% TUNEL ≠ 20\% SCSA).

Pros

Adds genomic integrity information absent from standard semen analysis.
Potentially modifiable: smoking cessation, antioxidant therapy, frequent ejaculation (< 2 day abstinence).
May guide ART strategy (IUI vs IVF vs ICSI).
Associations with recurrent pregnancy loss & poor embryogenesis (paternal genome activates day 2–3; oocyte repair may be overwhelmed).
Cons
Heterogeneous assays & cutoff definitions; evidence synthesis difficult.
Management guidelines for high SDF remain uncertain.
Additional financial cost; ethical concern over "IVF add-ons" without robust benefit proof.
Suggested selective use
- Clinical varicocele assessment
- Unexplained infertility with normal semen analysis
- Recurrent miscarriage cases.

2017 meta-analysis: linear sperm count decline of \approx52\% from 1973–2011; speculative link to environmental endocrine disruptors; media extrapolation to "zero sperm by 2045".
2021 critique: proposes "bio-variability" hypothesis
- Decline remains above WHO thresholds (mean 47 million ml⁻¹); may reflect natural temporal variability, not pathology.
- No demonstrated parallel drop in global fertility rates attributable solely to sperm parameters.
- Calls for more longitudinal, mechanistic research.

Spermatogenic cycle duration ≈ 74 days.
WHO lower reference limits: Volume 1.4 ml; Conc. 16 M ml⁻¹; Total 39 M; Prog. motility 30\%; Morphology 4\%.
OAT: Oligo (<16 M ml⁻¹), Astheno (<30\% prog), Terato (<4\% normal forms).
High SDF often defined >20–30\% (assay-specific).

Spermatogenesis is continuous, multi-stage, finishing in epididymis over \approx74 days.
Male infertility causes are anatomically & temporally classified; many remain idiopathic or unexplained.
Semen analysis, despite observer & biological variability, is the diagnostic cornerstone, utilising WHO fifth-percentile thresholds.
DNA fragmentation testing probes deeper sperm quality but its universal application remains controversial; presently advised in select clinical contexts.
Headlines on an impending sperm-count "apocalypse" are likely overstated; current data still fall within fertile ranges, though ongoing monitoring is prudent.