Underactive thyroid and male reproductive health

How Hashimoto’s and hypothyroidism affect men

A healthy thyroid is necessary for male reproductive health. The right amount of thyroid hormones will determine the fertility of men.

Testosterone levels will be lower if a thyroid is underactive, which means sperm count will be lower while testicles might be bigger (1–3). The hormone T3 is known to be essential for the maturation of testicles and testosterone production — if T3 is too low, there won’t be enough testosterone to support male fertility (4, 5).

Problems associated with an underactive thyroid and Hashimoto’s (6–8)

  • Low testosterone

  • Reduced forward sperm motility

  • Abnormal sperm morphology

  • Low high-quality sperm count

  • Increased prolactin levels

Why does the thyroid and Hashimoto’s affect sperm morphology?

Thyroid hormones are needed for proper functioning sperm cytoskeleton, a structure that provides mechanical support enabling sperm to move forward while maintaining sperm shape (6, 9).

Research has shown that abnormal sperm morphology (asthenozoospermia), low sperm count (asthenoteratozoospermia), or reduced sperm motility (oligoasthenoteratozoospermia), are connected to high TPO antibody levels (10).

Treatment with synthetic T4 (levothyroxine) can balance testosterone levels and improve sperm morphology and motility (10, 11).


  1. Krassas GE, et al. Thyroid disease and male reproductive function, 2003

  2. Krassas GE, et al. Male reproductive function in relation with thyroid alterations, 2004

  3. Wajner SM, et al. Clinical implications of altered thyroid status in male testicular function, 2009

  4. Jana NR, et al. Binding of thyroid hormone to goat testicular cell induces generation of a proteinaceous factor which stimulates androgen release, 1994

  5. Hsieh ML, et al. Cell growth effects of triiodothyronine and expression of thyroid hormone receptor in prostate carcinoma cells, 2005

  6. Corrales Hernández JJ, et al. Primary hypothyroidism and human spermatogenesis, 1999

  7. Krassas GE, et al. Hypothyroidism has an adverse effect on human spermatogenesis: a prospective, controlled study, 2008

  8. Clyde HR, et al. Elevated plasma testosterone and gonadotropin levels in infertile males with hyperthyroidism, 1976

  9. Zamoner A, et al. Propylthiouracil-induced congenital hypothyroidism upregulates vimentin phosphorylation and depletes antioxidant defences in immature rat testis, 2008

  10. Trummer H, et al. Thyroid hormones and thyroid antibodies in infertile males, 2001

  11. Donnelly P, et al. Testicular dysfunction in men with primary hypothyroidism; reversal of hypogonadotrophic hypogonadism with replacement thyroxine, 2000