The effects of male thyroid conditions on fertility

Thyroid conditions affect men too

In our companion article on female fertility, we discussed thyroid conditions and their effects on the female reproductive cycle and fertility — how an underactive (hypothyroidism) or overactive (hyperthyroidism) thyroid can make periods heavy, light, irregular, infrequent, or absent, and cause issues with implantation, maternal health, and fetal health. Those effects shape a woman’s ability to conceive and carry a healthy pregnancy to term.

Though thyroid conditions are often thought of as a women’s issue, men can be affected too — and, like in women, male hypothyroidism can affect fertility. Women are 5 to 8 times more likely to have hypothyroidism,¹ but an estimated 3–16% of men may have hypothyroidism, with risk rising as age increases.² Symptoms are similar between the sexes — fatigue, depression, constipation, cold intolerance, weight gain, dry skin — and hypothyroidism may also cause hair loss, low testosterone, muscle weakness and cramps, and sexual dysfunction.³

Both hypothyroidism and hyperthyroidism can affect a man’s fertility. In a study of men with hyper- and hypothyroidism, decreased libido, delayed ejaculation, and erectile dysfunction were all problematic — but after hypothyroid men were treated with L-thyroxine and hyperthyroid men with methimazole to normalize TSH, far fewer men reported these issues,⁴ showing that thyroid treatment can be largely successful.

Impaired spermatogenesis

Spermatogenesis is the process of sperm-cell development in the testes — central to fertility. Testosterone is needed to perform adequate spermatogenesis, maintain sperm count, and support sperm motility. Thyroid hormones regulate semen quality partly by adjusting serum testosterone, and they act alone or with follicle-stimulating hormone (FSH) and/or luteinizing hormone (LH) to modulate testes development, testosterone synthesis, and spermatogenesis.⁵ Thyroid receptors are found in various parts of the testes.

Impaired nitric oxide activity

Nitric oxide is a molecule the body produces that’s crucial for vasodilation — the relaxing of blood-vessel muscle that widens vessels and increases circulation, letting blood, oxygen, and nutrients move efficiently. That same process is essential to sexual health, because vasodilation is needed to attain and sustain an erection.⁹ Nitric oxide production is mediated by the thyroid,¹⁰ and hypothyroidism is associated with reduced nitric-oxide gene transcripts — which may help explain the erectile dysfunction linked to it.¹¹

Impaired sexual drive

A man’s thyroid can also significantly affect his libido. A lack of thyroid hormone can affect free-testosterone concentrations,¹² and low testosterone may contribute to low libido.¹³ The chain runs through the reproductive axis:

Thyroid autoimmunity, oxidative stress & male fertility

An autoimmune condition occurs when the immune system misidentifies part of the body as a threat. In autoimmune thyroid conditions like Hashimoto’s and Graves’ disease, the immune system attacks the thyroid — and that breakdown drives up oxidative stress (an imbalance between antioxidants and free radicals), which can affect other parts of the body, including the male reproductive system.

Thyroid conditions can contribute to male fertility issues alongside female ones. It’s important to check a man’s thyroid status — especially when he and his partner are struggling with infertility. Getting to the root cause of thyroid health is exactly what we do.