Genetics in premature ovarian failure and menopause

Oocytes are the female gametes, cells that, upon being fertilised by the sperm, will produce an embryo. In humans, the number of oocytes that females have throughout their lives is not unlimited; they are born instead with a limited number. These oocytes gradually run out in each menstruation until their supply becomes completely exhausted at menopause.

It is said that women suffer from premature ovarian failure when menstruation ceases because the oocyte supply has become exhausted at an earlier age than the age when the natural decline of ovarian function occurs (at 50, approximately). In cases where oocytes are still produced in women suffering from premature ovarian failure, they do not respond satisfactorily to the hormones responsible for their development and maturation.

Premature ovarian failure may have important consequences for women:

• Obviously, in their fertility: These women cannot conceive naturally and require assisted reproduction techniques in order to bear offspring. These patients also have a high risk that their oocytes will not respond to the In Vitro Fertilisation cycle, thus putting the success of the treatment in danger.
• On the other hand, the absence of female hormones due to low ovarian activity has serious consequences for health, mainly in cases of cardiovascular disease and osteoporosis.

The causes of ovarian failure remain unknown in 70-90% of the cases.

Premature ovarian failure may be due to:

• Genetic or chromosomal disorders.
• Autoimmune disorders.
• Enzyme disorders.
• Or external factors, such as surgical interventions, chemotherapy and radiation.

Among the genetic and chromosomal causes we find mainly 3 groups:

1. Abnormal karyotypes involving sex chromosome X. Either the number or the structure of this chromosome is not correct. Turner’s Syndrome is the most common abnormality. Affected women have just one X chromosome instead of two. It is a well known and well studied cause of infertility. In addition to reproductive problems, Turner’s Syndrome may produce abnormalities in the aorta, in addition to reproductive problems.
2. Fragile X Syndrome. This syndrome is the second most common cause of intellectual disability in males. Approximately, 20% of women who carry a premutation, an intermediate stage between normality and mutation, suffer from premature ovarian failure. These patients should receive genetic counselling, as, in addition to reproductive problems, they have a high risk of transmitting this pathology to their offspring.
3. Genetic polymorphisms: These are varieties regarded as normal. Yet, it has recently been proved that they are associated with premature ovarian failure.

At Instituto Bernabéu, we have created a Care Unit for patients who suffer from premature ovarian failure and a low ovarian response. This unit, allows patients to benefit from the latest innovations for individual diagnosis and treatment of reproductive problems and is meant to yield a better ovarian response.

Our results are very promising, and many of our patients, who would otherwise have to resort to oocyte donation, are achieving success.

MORE RELATED INFORMATION

• Premature Ovarian Failure, Can I be a mother? Causes, symptoms, diagnosis, treatment and prevention
• Poor ovarian responders treatment unit
• Accumulation of oocytes in patients with a low response
• Progress in treatment for patients with poor ovarian response
• What is the Ovarian Reserve? How important is it for fertility?
• Anti-Müllerian Hormone (AMH): Know the Age of your Ovaries
• Poor Ovarian Response: progress in genetics

Dr. José A. Ortiz, biochemist at IBBIOTECH, Instituto Bernabeu Group

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