Can uncontrolled thyroid conditions temporarily reduce sperm count?

Impact of Uncontrolled Thyroid Disease on Sperm Count

Yes, uncontrolled thyroid conditions can temporarily reduce sperm count, with abnormalities typically reversing after restoration of normal thyroid function. 1, 2

Mechanisms and Effects of Thyroid Dysfunction on Male Fertility

Hyperthyroidism

• Primary effects on sperm parameters:
  • Reduced sperm motility (most common finding) 3
  • Decreased semen volume
  • Reduced sperm density
  • Abnormal morphology 2

Hypothyroidism

• Primary effects on sperm parameters:
  • Primarily affects sperm morphology
  • May have more subtle effects than hyperthyroidism 1

Evidence for Reversibility

A prospective controlled study of hyperthyroid males demonstrated:

• Significantly lower sperm motility compared to controls (28% vs. 57%, p<0.01)
• After treatment and restoration of euthyroidism:
  • Sperm motility improved significantly (28% to 45%, p<0.05)
  • Sperm density showed improvement (35.7 to 43.3 x 10^6/ml) 3

Clinical Implications

For Infertility Evaluation

• Thyroid function testing should be included in the diagnostic workup of infertile men 2
• The American Urological Association and American Society for Reproductive Medicine recommend:
  • Evaluating for medical conditions associated with reproductive failure, including thyroid disorders 4
  • Considering thyroid function tests when indicated 4

For Treatment Approach

1. Primary goal: Restore euthyroidism

   • Abnormalities in sperm parameters typically reverse after normalization of thyroid function 1, 3

2. Timing considerations:

   • Allow 3-6 months after achieving euthyroidism for sperm parameters to improve
   • This timeframe corresponds to the spermatogenesis cycle

Special Considerations

Radioiodine Therapy

• May cause transient reductions in sperm count and motility
• Minimal risk of permanent effects if cumulative dose is less than 14 MBq 1

Severe Childhood Hypothyroidism

• Prolonged, severe hypothyroidism in childhood may cause permanent abnormalities in gonadal function 1

Clinical Pearls

• Thyroid dysfunction should be considered in all cases of unexplained male infertility
• Sperm abnormalities from thyroid dysfunction are generally reversible with appropriate treatment
• When evaluating male infertility, remember that normal semen parameters include:
  • Sperm concentration ≥16 million/mL
  • Total sperm number ≥39 million per ejaculate
  • Progressive motility ≥30%
  • Normal morphology ≥4% 4

The temporary nature of thyroid-induced sperm abnormalities offers a positive prognosis for affected men, with fertility typically improving once proper thyroid function is restored.