The main causes of male infertility can be divided into the following categories.

Sperm disorders

Problems with the production and maturation of sperm are the most common causes of male infertility. Sperm may be immature, abnormally shaped, or unable to move properly. Or, normal sperm may be produced in abnormally low numbers (oligospermia) or seemingly not at all (azoospermia). This problem may be caused by many different conditions including the following:

• infectious diseases or inflammatory conditions such as the mumps virus
• endocrine or hormonal disorders such as Kallmann’s syndrome or pituitary problem
• immunological disorders in which some men produce antibodies to their own sperm
• environmental and lifestyle factors
• genetic diseases (most are associated with sperm abnormalities, either directly or indirectly):
  cystic fibrosis – an inherited condition that typically involves the lungs and pancreas, but can present also as a cause of infertility with or without mild sinus problems. Most men who have cystic fibrosis have obstructive azoospermia because they were born without a vas deferens. This results in male infertility.
• Noonan syndrome – an inherited condition which can occur in either males or females. In males, this syndrome can cause abnormal gonadal (testicular) function.
• myotonic dystrophy – an inherited condition with progressive multi-system involvement, resulting in infertility (underdeveloped testes and abnormal sperm production), in some cases.
• hemochromatosis – an inherited condition affecting iron storage. Eighty percent of men with hemochromatosis have testicular dysfunction.
• sickle cell disease – an inherited condition affecting the normal production of hemoglobin.
• sex reversal syndrome – a male who has the sex chromosomes of a genetic female (XX, instead of XY), resulting in azoospermia and other characteristics.
• androgen receptor gene mutations – an inherited condition in which a man is genetically male (46,XY), but has infertility due to a defect in receptors for testosterone.
• chromosomal abnormalities – men with an extra X sex chromosome, known as Klinefelter syndrome, often do not produce sperm or produce very low quantities of sperm.
• chromosome rearrangements – in some persons, there are the usual number of chromosomes (46) in the nucleus (center) of cells, but rearrangements in the chromosome material, where a piece of a chromosome has exchanged places with another, has taken place; men with either azoospermia or oligospermia have a higher frequency of chromosome rearrangements than is found in the general population.
• deletions in the Y chromosome – in some persons, there are the usual number of chromosomes (46) in the body cells, but small sections of the Y chromosome are missing or deleted; a small percentage of men with either azoospermia or oligospermia have deletions in the Y chromosome.It is important to understand that men who have genetic problems which cause their infertility, such as a deletion in the Y chromosome, can pass this problem to their sons, who would also have infertility, if they elect to use their own sperm in achieving a pregnancy.

Anatomical abnormalities

• Obstructions of the genital tract can cause infertility by partially or totally blocking the flow of seminal fluid. Some of these abnormalities may be of congenital (present at birth) origin or the result of a genetic defect. Others could have occurred due to infection or inflammation of the urogenital tract, surgery that left scar tissue in the genital tract, or the presence of varicose veins in the scrotum (scrotal varicoceles).
• immotile cilia syndromes
• In this condition, the sperm count is normal but the spermatozoa are non-motile such as in Kartagener’s syndrome, an inherited disorder.
  mitochondrial deletions
• Mitochondria are structures in the cell responsible for energy production. There are actually a set of genes in the mitochondria, separate from the normal chromosome set contained in the nucleus. Recently, it has been discovered that these genes, when altered or deleted, can affect a person’s health and/or fertility.
  liver disease, renal disease, or treatment for seizure disorders

Other factors

Other factors may arise from the defective delivery of sperm into the female genital tract, which could be caused by impotence or premature ejaculation.

How is male factor infertility diagnosed?

In addition to a complete medical history and physical examination, diagnostic testing for male factor infertility may include the following:

• multiple semen analysis – at least two semen examples are collected on separate days to examine the semen and sperm for various factors, such as semen volume, consistency, and pH, and the sperm count, motility, and morphology (shape).
• other tests (to determine the cause of sperm abnormalities or diseases of the male reproductive system)