Hypothyroidism's Impact on Male Fertility and Treatment Approaches
Hypothyroidism significantly impairs male fertility through multiple mechanisms, and treatment with levothyroxine to normalize thyroid function is the most effective approach to restore fertility in affected men.
Effects of Hypothyroidism on Male Fertility
- Hypothyroidism disrupts the male reproductive system by causing hypergonadotropism (elevated LH and FSH levels) with paradoxically low serum testosterone levels 1
- Men with untreated hypothyroidism demonstrate reduced sperm motility and abnormal sperm morphology, directly affecting fertility potential 1
- Low sex hormone-binding globulin (SHBG) levels are observed in hypothyroid men, further disrupting hormonal balance necessary for normal reproductive function 1
- Hypothyroid men show subnormal testosterone response to human chorionic gonadotropin (hCG) stimulation, indicating impaired testicular function 1
- Thyroid hormone deficiency can lead to erectile abnormalities, contributing to fertility challenges 2
Diagnostic Approach
- Diagnosis of hypothyroidism in men with fertility concerns requires biochemical testing, with elevated TSH and low free T4 indicating overt primary hypothyroidism 3
- Assessment should include evaluation for pituitary disorders, surgical history, comorbidities, and medications affecting the hypothalamic-pituitary-gonadal axis 4
- Physical examination should include BMI and waist circumference measurement, as obesity can contribute to both hypothyroidism and fertility issues 4
- Evaluation should check for drugs and substances that may interfere with testosterone production/action 4
- Men with decreased libido, impotence, or testosterone deficiency with low/low-normal LH levels should have serum prolactin measured to investigate hyperprolactinemia 4
Treatment Recommendations
- First-line treatment for hypothyroidism-related male infertility is synthetic levothyroxine to normalize TSH levels, which can restore reproductive endocrine function and improve sperm parameters 3, 1
- Thyroxine replacement therapy has been shown to normalize elevated gonadotropins (LH, FSH), increase testosterone levels, normalize SHBG, and improve testosterone response to hCG 1
- Levothyroxine treatment leads to measurable improvements in sperm count and motility in previously hypothyroid men 1
- Testosterone monotherapy should NOT be prescribed for men with hypothyroidism who are interested in current or future fertility, as it can suppress spermatogenesis 4
- For men with hypothyroidism and hypogonadotropic hypogonadism (HH), treatment should first address the thyroid dysfunction before considering gonadotropin therapy 4
Treatment Monitoring and Considerations
- Thyroxine dosing should be tailored to patient-specific factors, with TSH monitoring performed 6-8 weeks after initiating treatment or changing dose 3
- Once TSH levels are normalized with levothyroxine treatment, annual monitoring is recommended to avoid overtreatment or undertreatment 3
- If fertility does not improve after achieving euthyroid status, additional fertility treatments may be considered, including assisted reproductive technologies (ART) 4
- For men with persistent fertility issues despite normalized thyroid function, referral to a reproductive endocrinologist or male reproductive specialist is recommended 4
- Fertility concerns must be considered when managing hypothyroidism, as treatment approaches differ between men seeking fertility versus those who are not 4
Important Caveats
- Testosterone therapy is absolutely contraindicated in men with hypothyroidism seeking fertility, as it provides negative feedback to the hypothalamus and pituitary, inhibiting gonadotropin secretion and potentially causing azoospermia 4
- Thyroid function testing should be avoided during acute illness, as results may be misleading 4
- Both untreated hypothyroidism and overtreatment with levothyroxine can have adverse effects on cardiovascular health and fertility 3
- Once adequately treated, hypothyroidism should not significantly impact fertility in most cases 5
- Fertility treatment decisions should consider both partners, as female factors may also contribute to infertility 4