Obesity genes and infertility
The obesity genes primarily affect common pathways in lipid metabolism, deposition or transport, eating behavior and food selection, physical activity or energy expenditure. Twenty-one of the obesity genes are also associated with human infertility and reproduction.
Even significant evidence for linkage between obesity and female fertility were found, the clear mechanism have not been found yet.
Association between obesity and infertility
Obesity leads to infertility in both men and women. This is primarily due to excess estrogen (female sex hormones) interfering with normal ovulation in women and altering spermatogenesis (sperm production) in men. It is believed to cause 6%of primary infertility.
Obesity was found to be associated with female infertility. The most frequent anovulatory cycles (cycles without ovulation) are related to polycystic ovary syndrome (PCOS) occurrence, commonly associated with obesity and hormonal disturbances in the course of obesity.
Obesity was also found to be associated with male infertility related to erectile dysfunction, hormonal disturbances and a reduction in sperm count and quality.
Erectile dysfunction (ED), a kind of male sexual dysfunction, is characterized by the inability to achieve or maintain erections of the penis potent for satisfaction during sexual activity1. Even though ED is not a fatal condition, it interferes with daily routine, social interactions and quality of life of the patient. The risk factors of erectile dysfunction include obesity grade, visceral obesity, low testosterone level, and physical inactivity.
Obesity-related hormonal disturbances are not restricted to androgen deficiency. It was suggested that decreased sex hormone-binding globulin (SHBG) and increased free testosterone levels in consequence favor testosterone to estradiol conversion in adipose tissue. Decreased testosterone-to-estradiol ratio contributes to impaired spermatogenesis and infertility development.
Both obesity and infertility are the important risk factors of psychological disturbances and poor quality of life among women and men in reproductive age. On the other hand, the mood disorders may exacerbate the hormonal disturbances and worsen the effectiveness of infertility management.
Obese patients undergoing IVF or intracytoplasmic sperm injection (ICSI) treatment are known to have increased follicle-stimulating hormone (FSH) requirement, fewer collected oocytes, and frequent cycle cancellation, lower pregnancy rate and increase miscarriage rate than their non-obese counterpart.