By Laura Garrido BSc, MSc (embryologist).
Last Update: 10/23/2014

Infertility affects 1 in every 6 couples that are of childbearing age. We can divide infertility causes into: 30% male causes, 30% female causes, 20% causes of both and 20% unexplained infertility or unknown reasons, in which the causes of infertility could not be determined.

Pre-testicular origin

The brain must send the right endocrine signals so that the sperm production can take place. All the process must be coordinated and if this communication does not happen, it will cause male infertility.

Diabetes and infertility

According to several studies on infertility, the high concentration of sugar in blood can have a negative impact on the quality of sperms. Diabetes increases the damage produced to the DNA of sperms, which means a lower rate of pregnancy and an augment of low quality embryos.

Thyroid problems

The thyroid gland is in charge of several metabolic processes such as oxygen consumption, protein production and hormones sensitization.

A change in its way of functioning, such as hyperthyroidism or thyroid gland failure can affect male infertility since they interfere with the sperm maturation.

Thyroid gland failure can also provoke changes in the sperm morphology, a decrease of sexual desire and erectile dysfunction. However, it can be treated.

Hypogonadotropic hypogonadism

It is caused by an insufficient production of pituitary gland hormones, which are responsible for the production of sperm. There is a hormonal hierarchy which begins in the hypothalamus.

The hypothalamus sends signals that are received by the pituitary gland, which sends signals to the testicle and finally the testicle sends signals to the hypothalamus. Kallman syndrome is a hypogonadotropic hypogonadism in which a loss of the sense of smell also takes place.

Hyperprolactinemia

There must be a balance between the lactogenic hormone and the gonadotropins (hormones that produce sperm). When there is an increase in the lactogenic hormone, the production of the FSH and the LH is reduced, which consequently has an impact on the spermatogenesis or production of sperm.

Testicular origin

The production of sperm is divided in several stages, during which the genetic material is split up. Later on, it gets modified until it acquires the aspect and becomes the sperm as we know it.

Y chromosome genetic disorders

The Y chromosome is the smallest of the male chromosomes and it contains the genes responsible for the formation of the testicles, in the AZF chromosome region.

Males that have had damage in this region, such as the absence of some important genes, suffer from complete azoospermia or many problems in the formation of sperm. If they manage to have children, which is highly unlikely, they would transmit the Y chromosome genetic disorder to their descendants.

Klinefelter syndrome

It is a disorder in the chromosomes, in which the man presents an extra X chromosome. His karyotype is 46XXY instead of 46XY. This causes a decrease on the quantity of testosterone, which makes it impossible for the spermatogenesis to take place.

A treatment with testosterone is applied, so that males will develop secondary male characteristics and avoid problems in adaptation, resolution of conflicts and learning problems, which are commonly linked to this syndrome. Nonetheless, the testosterone treatment does not solve infertility.

Cryptorchidism

It is a congenital birth defect in which one of the testicles does not descend to the scrotal bag. The descent must be performed surgically at an early age, because due to the fact that the body temperature is higher than the one to which testicles are exposed, it prevents a properly sperm formation.

Varicocele

There is an inflammation of the vessels that drain the testicles. It causes a reflux that increases the testicular temperature and this rise in the temperature might provoke the non-formation of sperm.

The hypotheses, that a surgical intervetion may improve the seminal analysis or that the low quality may be maintained despite the intervention, are still controversial.

Hydrocoele

The testicles are surrounded by a fluid that makes them less vulnerable to any blow. Sometimes this liquid increases due to a testicle inflamation.

The obstruction of blood or lymphatic vessels may be the cause behind this increase. Even though the accumulation of fluid does not cause infertility in itself, it may be a symptom of something else that might cause it.

Gonadal dysgenesis

Even though the chromosomes are those associated with males, the subject presents vagina, uterus and Fallopian tubes but no sexual organs are developed.

The male or female gonads are not functional. These subjects are women that don’t have the period and when a genetic study is carried out, it leads to the fact that they are men. Even though some of them may have hypoplastic uterus or an infant matrix, which are not functional, pregnancy in women XY with mature uterus has been successful thanks to egg donation.

Post-testicular origin

When the sperms are already formed, they need to mature in order to be able to impregnate. This maturation begins within the testicles and carries on in the female gonad, during a process named capacitation.

The sperms, with their characteristic morphology, exit the seminiferous tubule then go through the vasa deferentia until they reach the epididymis, where their motility will be activated and where they will gather until the ejaculation takes place. D

uring ejaculation they will go through the vasa deferentia − the ones that are cut when a vasectomy is performed − and they will reach the penis. There they will mix with the secretions of the connected glands and will exit the penis through the urethra.

Obstruction in the vasa deferentia, cystic fibrosis

Cystic fibrosis is a genetic disorder that affects 5% of the total population and provokes obstructive azoospermia. It is due to the fact that the vasa deferentia − the ones carrying the sperm from the testicles to the penis − weren’t properly formed during the fetal development. It is a recessive inheritance monosomic illness, and even though sperms are produced normally, they don’t reach the urethra because the vasa deferentia are missing.

Immunologic infertility

Antibodies against the sperm are produced, causing the sperms to adhere to each other and thus making motility and egg fertilisation more difficult.

One of the main causes for this immune reaction is the loss or break of the blood-testes barrier that keeps the sperms − that have a different genetic content – apart from the rest of the organism cells. However, damage is occasionally induced in the compartmentalisation, and the cells react as if the sperms were an alien element in the organism.

Retrograde ejaculation

During normal ejaculation, the sphincter closes the bladder and due to the pressure difference, the sperms exit through the urethra.

During retrograde ejaculation there’s a dysfunction of this sphincter, which provokes that the semen is ejaculated into de bladder. This disorder prevents pregnancy but is easily solvable.

Hypospadias

It is a genetic malformation in which the urinary meatus (orifice on the penis) is not located on the glans but on the body of the penis or even on the testicles.

It is due to an insufficient concentration of male hormones. When it is mild it does not prevent from getting pregnant, but when it is severe it may prevent the sperms from settling into the vagina.

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Authors and contributors

 Laura Garrido
BSc, MSc
Embryologist
Bachelor's Degree in Biotechnology from the Pablo de Olavide University (UPO) of Seville, Spain. Master's Degree in Biotechnology of Human Assisted Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI). Experience at IVF, andrology, and general analysis laboratories. Embryologist specialized in Assisted Reproduction. More information
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