Infertility affects many couples, and a male factor is involved in about half of cases, either alone or alongside a female factor, so it is common and not a reason for shame. The most frequent issue is a problem with sperm number, movement, or shape.
Causes include varicocele (enlarged veins in the scrotum), hormonal imbalances including low testosterone driven by other glands, past infections, undescended testes in childhood, certain medications and anabolic steroids, genetic conditions, blockages in the tubes, and lifestyle factors such as smoking, heavy alcohol, obesity, heat exposure, and some recreational drugs. Notably, taking testosterone supplements or TRT can suppress sperm production.
If you have been trying to conceive for around a year without success (or six months if the female partner is over 35), see a doctor. Assessment usually starts with a semen analysis and hormone tests, and many causes are treatable. Both partners should be evaluated together.