Infertility in men can be caused by different factors and is typically evaluated by a semen analysis. When a semen analysis is performed, the number of sperm (concentration), motility (movement), and morphology (shape) are assessed by a specialist. A slightly abnormal semen analysis does not mean that a man is necessarily infertile. Instead, a semen analysis helps determine if and how male factors are contributing to infertility.
Disruption of testicular or ejaculatory function
- Varicoceles, a condition in which the veins on a man’s testicles are large and cause them to overheat. The heat may affect the number or shape of the sperm.
- Trauma to the testes may affect sperm production and result in lower number of sperm.
- Unhealthy habits such as heavy alcohol use, smoking, anabolic steroid use, and illicit drug use.
- Use of certain medications and supplements.
- Cancer treatment involving the use of certain types of chemotherapy, radiation, or surgery to remove one or both testicles
Medical conditions such as diabetes, cystic fibrosis, certain types of autoimmune disorders, and certain types of infections may cause testicular failure.
- Improper function of the hypothalamus or pituitary glands. The hypothalamus and pituitary glands in the brain produce hormones that maintain normal testicular function. Production of too much prolactin, a hormone made by the pituitary gland (often due to the presence of a benign pituitary gland tumor), or other conditions that damage or impair the function of the hypothalamus or the pituitary gland may result in low or no sperm production.
- These conditions may include benign and malignant (cancerous) pituitary tumors, congenital adrenal hyperplasia, exposure to too much estrogen, exposure to too much testosterone, Cushing’s syndrome, and chronic use of medications called glucocorticoids.
Genetic conditions such as a Klinefelter’s syndrome, Y-chromosome microdeletion, myotonic dystrophy, and other, less common genetic disorders may cause no sperm to be produced, or low numbers of sperm to be produced.
- Age. Although advanced age plays a much more important role in predicting female infertility, couples in which the male partner is 40 years old or older are more likely to report difficulty conceiving.
- Being overweight or obese.
- Excessive alcohol use.
- Use of marijuana.
- Exposure to testosterone. This may occur when a doctor prescribes testosterone injections, implants, or topical gel for low testosterone, or when a man takes testosterone or similar medications illicitly for the purposes of increasing their muscle mass.
- Exposure to radiation.
- Frequent exposure of the testes to high temperatures, such as that which may occur in men confined to a wheelchair, or through frequent sauna or hot tub use.
- Exposure to certain medications such as flutamide, cyproterone, bicalutamide, spironolactone, ketoconazole, or cimetidine.
- Exposure to environmental toxins including exposure to pesticides, lead, cadmium, or mercury.
The most common causes of female infertility include problems with ovulation, damage to fallopian tubes or uterus, or problems with the cervix. Age can contribute to infertility because as a woman ages, her fertility naturally tends to decrease.
Ovulation problems may be caused by one or more of the following
- A hormone imbalance
- A tumor or cyst
- Eating disorders such as anorexia or bulimia
- Alcohol or drug use
- Thyroid gland problems
- Excess weight
- Intense exercise that causes a significant loss of body fat
- Extremely brief menstrual cycles
Damage to the fallopian tubes or uterus can be caused by one or more of the following
- Pelvic inflammatory disease
- A previous infection
- Polyps in the uterus
- Endometriosis or fibroids
- Scar tissue or adhesions
- Chronic medical illness
- A previous ectopic (tubal) pregnancy
- A birth defect
- DES syndrome (The medication DES, given to women to prevent miscarriage or premature birth can result in fertility problems for their children.)
Abnormal cervical mucus can also cause infertility. Abnormal cervical mucus can prevent the sperm from reaching the egg or make it more difficult for the sperm to penetrate the egg.
Female fertility is known to decline with
- Age. More women are waiting until their 30s and 40s to have children. In fact, about 20% of women in the United States now have their first child after age 35. About one-third of couples in which the woman is older than 35 years have fertility problems. Aging not only decreases a woman’s chances of having a baby, but also increases her chances of miscarriage and of having a child with a genetic abnormality.
- Aging decreases a woman’s chances of having a baby in the following ways:
- She has a smaller number of eggs left.
- Her eggs are not as healthy.
- She is more likely to have health conditions that can cause fertility problems.
- She is more likely to have a miscarriage.
- Excessive alcohol use.
- Extreme weight gain or loss.
- Excessive physical or emotional stress that results in amenorrhea (absent periods).