When it comes to a woman’s fertility and reproduction, many factors play a role. Did you know it is not just the ovaries or the uterus you need to know about, and that a part of your brain plays a major role too? A miscommunication in the HPO axis can cause issues with both menstruation and fertility. Wondering what it is? Read on to find out.
The Hypothalamic-Pituitary-Ovarian (HPO) axis is a vital regulatory system in the female reproductive system. It involves the hypothalamus in the brain, the pituitary gland located just below it, which releases key reproductive hormones, and the ovaries—the organs responsible for producing eggs and sex hormones.
The HPO axis regulates a woman’s reproductive system through her hormones. When the HPO axis does not function fully, it can lead to irregular menstrual periods, unpredictable menstrual cycles, developmental issues and even infertility.
The hypothalamus in the brain releases GnRH - gonadotropin-releasing hormone, which stimulates the pituitary gland to release the two important hormones responsible for female sexual development - FSH - follicle-stimulating hormone and LH - luteinising hormone. These hormones together then stimulate the ovaries to ovulate and produce the two female sex hormones – estrogen and progesterone, which are responsible for regulating a female’s menstrual cycle and reproduction process.
When the hypothalamus gland releases GnRH, the hormone will travel down to the pituitary gland. Now stimulated by the GnRH, the pituitary gland will release FSH to stimulate the growth and maturation of the ovarian follicles that house the eggs. It will also release LH to trigger ovulation – the release of a mature egg from the ovarian follicles.
The FSH and LH also stimulate the ovaries to produce estrogen and progesterone hormones, which regulate the menstrual cycle. These two hormones prepare the endometrium in the uterus to receive a fertilised egg and support pregnancy.
HPO axis is the communication between the three important parts of the female reproductive system – the hypothalamus, pituitary and ovaries. A disruption or an imbalance in this communication can cause issues.
The HPO axis is responsible for the menstrual cycle. The communication between these three players has to be smooth for the ovulation to occur at the right time every month.
Now, the communication channel does not just start with the hypothalamus and end with the ovaries. The ovaries give feedback to the hypothalamus and pituitary gland.
When the feedback from the ovaries to the hypothalamus is positive, it will stimulate the GnRH release, and the cycle will continue. When the feedback is negative, it will suppress the release of GnRH, which in turn will suppress the release of FSH and LH. This negative feedback will prevent excessive growth of the follicles and keep the menstrual cycle consistent and healthy.
The feedback is negative for most of the menstrual cycle. It becomes positive and peaks just before ovulation, thus stimulating the release of the egg. After the release, the hormone production decreases until the next ovulation.
This shows how important the HPO axis is for female fertility. A small miscommunication or lack of communication between these factors of the HPO axis can cause inconsistent periods and affect ovulation.
Ovulation disorders are the leading cause of infertility in women. This can be further classified into three types. Group 1 refers to issues caused by the failure of the hypothalamus, and group 3 refers to ovarian insufficiency.
For the context of this blog, we will discuss group 2 in detail.
Group 2 – This category comprises dysfunction of the HPO axis. About 85% of ovulation disorders are caused by PCOS, abnormal BMI, and endocrinopathies. A woman’s menstrual cycle is closely regulated by the HPO axis for follicle selection. If any issues occur inside this HPO axis, it can negatively impact the entire regulation process.
In most cases, the fertility issues caused by group 2 of ovarian disorders or HPO dysfunction are reversible. This means proper treatment at the right time can help most women get pregnant. Some may need a little extra help through fertility or other therapies.
HPO failure or premature ovarian failure can be due to the following reasons:
● autoimmune conditions
● genetic disorders
● infections
● environmental toxins
● Drastic changes in weight or BMI
When the communication between the members of the HPO axis is not smooth or faces disturbances, it can lead to the following:
● Metabolic disorders
● Infertility
● Reproductive disorders
Since these are essential hormones for the optimal functioning of the body, the impact of HPO dysfunction extends beyond reproductive health. Some of them are:
● Growth retardation or excess growth in children
● Increase the risk of osteoporosis in young females
● Insulin resistance
● Depression, anxiety, and mood swings
As the HPO axis relates to the hormone production in the body, a typical diagnosis of HPO axis dysfunction involves hormone testing. The tests will stimulate and evaluate the HPO axis’s response to understand where the problem is.
Dysfunction of the HPO axis is treated by addressing the underlying condition, like stress, nutrition or lifestyle, which could trigger the imbalance. Hormone replacement therapy can also help restore the balance and functioning of the HPO axis.
The HPO axis is a crucial part of the female reproductive system. It regulates menstruation, ovulation and pregnancy by releasing hormones in coordination. A small disturbance in this system can cause various issues related to reproduction in females. The proper functioning of this system is very important.
