In males, the production of sex cells, also known as spermatogenesis, begins at puberty. Several hundred million sperm are produced each day in the testes from stem cells (spermatogonia) located at the periphery of the seminiferous tubules. The complete process takes about 74 days until the mature sperm detaches from the tubule wall and migrates to the epididymis where it will be stored afterwards. Testosterone, produced in nearly constant concentrations in the testes by Leydig cells, is essential for spermatogenesis. This production is controlled by the brain at the level of the hypothalamic-pituitary complex, which releases two hormones into the blood: FSH and LH. LH acts on the Leydig cells to stimulate the production of testosterone in the testes. FSH acts on the seminiferous tubules. There is also a feedback loop controlling testosterone synthesis in the brain. The higher its concentration, the lower the production of FSH and LH and vice versa. What are the causes of male infertility? Testicular failure Abnormalities of spermatogenesis are one of the most common causes of male infertility. Abnormalities may relate to the quantity or quality of sperm. In practice, sperm abnormalities are becoming better diagnosed, but their relevance to infertility is not always well established. Azoospermia Azoospermia corresponds to the complete absence of sperm. Oligospermia is characterized by a very low sperm count. Teratospermia is due to morphological abnormalities that can impair sperm motility and functionality. These anomalies can be: Constitutional – primary, arising for example from a genetic mutation; Acquired after diseases such as orchitis, accidents – trauma, twisting of the testicles and others; Secondary to treatment such as chemotherapy or radiotherapy, the effects of which may be irreversible; Related to the use of drugs. Primary deficiencies of spermatogenesis may have a genetic origin, disrupting the structure of spermatozoa or the molecular elements necessary for their functions. Chromosomal abnormalities are found in 5% of men affected by infertility. Most often, this involves abnormalities of the sex chromosomes, the most common of which is the chromosomal abnormality associated with Klinefelter syndrome. In the absence of AZFa, the Y chromosome region highlights another abnormality known to normally cause the absence of germ cells in the seminiferous tubules. Changes in the structure of autosomes – non-sex chromosomes are also associated with abnormalities in spermatogenesis, which leads to the formation of abnormal sperm, unable to fertilize a mature egg. For example, deletion of the DEFB 126 gene causes a deficiency of a glycoprotein called defensin. Defensin is normally attached to the membrane of spermatozoa during their passage through the epididymis,facilitating their transport into the female genital tract and thereby protecting them from the female immune system. In many cases, no cause has been found to explain the sperm changes associated with male infertility. In addition, testicular cancer cases are increasing by 1.5% per year, with no known cause, and those of cryptorchidism are increasing by 2.6% per year. Cryptorchidism is characterized by the absence of one or both testicles in the scrotum. Operated or not, cryptorchidism is often associated with changes in spermatogenesis in adults. This anomaly may be due to an insufficient level of male sex hormones – androgens during development, which may be the result of exposure of the mother to agents affecting the endocrine glands during pregnancy or exposure to toxic substances in previous generations. Sexual dysfunction In addition to erectile and ejaculation disorders of psychogenic origin, also a number of vascular, hormonal, metabolic or neurological factors can lead to sexual dysfunction. This is observed, for example, in lesions of the spinal cord responsible for ejaculation or retrograde ejaculation. Infertility can be overcome quite easily when it is possible to detect sperm in the urine or to stimulate the ejaculation in an appropriate way to achieve suitable conditions for assisted reproduction. Hypothalamic-pituitary diseases Some causes of sperm abnormalities are hypothalamic-pituitary diseases. They are responsible for a change in hormone production that can lead to a deficiency in sperm production. Some therapeutic approaches Cancers of the reproductive organs and some cancer treatments, such as chemotherapy, can lead to infertility. In addition, recent studies have shown that certain drugs that are generally well tolerated, such as analgesics, antihistamines or antireflux drugs, can also, under certain conditions, have an impact on reproductive function. Environmental factors Smoking has a negative role at every stage of reproduction, in both women and men, because it is associated with impaired semen quality. These harmful effects are probably related to the oxidative stress induced by the tobacco components. Mental factors Stress acts at the brain level by altering the production of neurohormones and/or gonadotropic hormones in the hypothalamic-pituitary system. Body weight Several epidemiological studies have observed an association between body weight, body mass index, and fertility disorders. In men, overweight and obesity are associated with altered sperm parameters. References: https://www.inserm.fr/dossier/infertilite/and those of cryptorchidism increased by 2.6% per year. Cryptorchidism is characterized by the absence of one or both testicles in the scrotum. Operated or not, cryptorchidism is often associated with changes in spermatogenesis in adults. This anomaly may be due to an insufficient level of male sex hormones – androgens during development, which may be the result of exposure of the mother to agents affecting the endocrine glands during pregnancy or exposure to toxic substances in previous generations. Sexual dysfunction In addition to erectile and ejaculation disorders of psychogenic origin, also a number of vascular, hormonal, metabolic or neurological factors can lead to sexual dysfunction. This is observed, for example, in lesions of the spinal cord responsible for ejaculation or retrograde ejaculation. Infertility can be overcome quite easily when it is possible to detect sperm in the urine or to stimulate the ejaculation in an appropriate way to achieve suitable conditions for assisted reproduction. Hypothalamic-pituitary diseases Some causes of sperm abnormalities are hypothalamic-pituitary diseases. They are responsible for a change in hormone production that can lead to a deficiency in sperm production. Some therapeutic approaches Cancers of the reproductive organs and some cancer treatments, such as chemotherapy, can lead to infertility. In addition, recent studies have shown that certain drugs that are generally well tolerated, such as analgesics, antihistamines or antireflux drugs, can also, under certain conditions, have an impact on reproductive function. Environmental factors Smoking has a negative role at every stage of reproduction, in both women and men, because it is associated with impaired semen quality. These harmful effects are probably related to the oxidative stress induced by the tobacco components. Mental factors Stress acts at the brain level by altering the production of neurohormones and/or gonadotropic hormones in the hypothalamic-pituitary system. Body weight Several epidemiological studies have observed an association between body weight, body mass index, and fertility disorders. In men, overweight and obesity are associated with altered sperm parameters. References: https://www.inserm.fr/dossier/infertilite/and those of cryptorchidism increased by 2.6% per year. Cryptorchidism is characterized by the absence of one or both testicles in the scrotum. Operated or not, cryptorchidism is often associated with changes in spermatogenesis in adults. This anomaly may be due to an insufficient level of male sex hormones – androgens during development, which may be the result of exposure of the mother to agents affecting the endocrine glands during pregnancy or exposure to toxic substances in previous generations. Sexual dysfunction In addition to erectile and ejaculation disorders of psychogenic origin, also a number of vascular, hormonal, metabolic or neurological factors can lead to sexual dysfunction. This is observed, for example, in lesions of the spinal cord responsible for ejaculation or retrograde ejaculation. Infertility can be overcome quite easily when it is possible to detect sperm in the urine or to stimulate the ejaculation in an appropriate way to achieve suitable conditions for assisted reproduction. Hypothalamic-pituitary diseases Some causes of sperm abnormalities are hypothalamic-pituitary diseases. They are responsible for a change in hormone production that can lead to a deficiency in sperm production. Some therapeutic approaches Cancers of the reproductive organs and some cancer treatments, such as chemotherapy, can lead to infertility. In addition, recent studies have shown that certain drugs that are generally well tolerated, such as analgesics, antihistamines or antireflux drugs, can also, under certain conditions, have an impact on reproductive function. Environmental factors Smoking has a negative role at every stage of reproduction, in both women and men, because it is associated with impaired semen quality. These harmful effects are probably related to the oxidative stress induced by the tobacco components. Mental factors Stress acts at the brain level by altering the production of neurohormones and/or gonadotropic hormones in the hypothalamic-pituitary system. Body weight Several epidemiological studies have observed an association between body weight, body mass index and fertility disorders. In men, overweight and obesity are associated with altered sperm parameters. References: https://www.inserm.fr/dossier/infertilite/Sexual dysfunction In addition to erectile and ejaculation disorders of psychogenic origin, also a number of vascular, hormonal, metabolic or neurological factors can lead to sexual dysfunction. This is observed, for example, in lesions of the spinal cord responsible for ejaculation or retrograde ejaculation. Infertility can be overcome quite easily when it is possible to detect sperm in the urine or to stimulate the ejaculation in an appropriate way to achieve suitable conditions for assisted reproduction. Hypothalamic-pituitary diseases Some causes of sperm abnormalities are hypothalamic-pituitary diseases. They are responsible for a change in hormone production that can lead to a deficiency in sperm production. Some therapeutic approaches Cancers of the reproductive organs and some cancer treatments, such as chemotherapy, can lead to infertility. In addition, recent studies have shown that certain drugs that are generally well tolerated, such as analgesics, antihistamines or antireflux drugs, can also, under certain conditions, have an impact on reproductive function. Environmental factors Smoking has a negative role at every stage of reproduction, in both women and men, because it is associated with impaired semen quality. These harmful effects are probably related to the oxidative stress induced by the tobacco components. Mental factors Stress acts at the brain level by altering the production of neurohormones and/or gonadotropic hormones in the hypothalamic-pituitary system. Body weight Several epidemiological studies have observed an association between body weight, body mass index, and fertility disorders. In men, overweight and obesity are associated with altered sperm parameters. References: https://www.inserm.fr/dossier/infertilite/Sexual dysfunction In addition to erectile and ejaculation disorders of psychogenic origin, also a number of vascular, hormonal, metabolic or neurological factors can lead to sexual dysfunction. This is observed, for example, in lesions of the spinal cord responsible for ejaculation or retrograde ejaculation. Infertility can be overcome quite easily when it is possible to detect sperm in the urine or to stimulate the ejaculation in an appropriate way to achieve suitable conditions for assisted reproduction. Hypothalamic-pituitary diseases Some causes of sperm abnormalities are hypothalamic-pituitary diseases. They are responsible for a change in hormone production that can lead to a deficiency in sperm production. Some therapeutic approaches Cancers of the reproductive organs and some cancer treatments, such as chemotherapy, can lead to infertility. In addition, recent studies have shown that certain drugs that are generally well tolerated, such as analgesics, antihistamines or antireflux drugs, can also, under certain conditions, have an impact on reproductive function. Environmental factors Smoking has a negative role at every stage of reproduction, in both women and men, because it is associated with impaired semen quality. These harmful effects are probably related to the oxidative stress induced by the tobacco components. Mental factors Stress acts at the brain level by altering the production of neurohormones and/or gonadotropic hormones in the hypothalamic-pituitary system. Body weight Several epidemiological studies have observed an association between body weight, body mass index, and fertility disorders. In men, overweight and obesity are associated with altered sperm parameters. References: https://www.inserm.fr/dossier/infertilite/to affect reproductive function. Environmental factors Smoking has a negative role at every stage of reproduction, in both women and men, because it is associated with impaired semen quality. These harmful effects are probably related to the oxidative stress induced by the tobacco components. Mental factors Stress acts at the brain level by altering the production of neurohormones and/or gonadotropic hormones in the hypothalamic-pituitary system. Body weight Several epidemiological studies have observed an association between body weight, body mass index, and fertility disorders. In men, overweight and obesity are associated with altered sperm parameters. References: https://www.inserm.fr/dossier/infertilite/to affect reproductive function. Environmental factors Smoking has a negative role at every stage of reproduction, in both women and men, because it is associated with impaired semen quality. These harmful effects are probably related to the oxidative stress induced by the tobacco components. Mental factors Stress acts at the brain level by altering the production of neurohormones and/or gonadotropic hormones in the hypothalamic-pituitary system. Body weight Several epidemiological studies have observed an association between body weight, body mass index, and fertility disorders. In men, overweight and obesity are associated with altered sperm parameters. References: https://www.inserm.fr/dossier/infertilite/