To understand the biology of conception, it is useful to know the relationship between ovulation and menstruation. Read on to find out why regular ovulation is responsible for regular menstruation.
About Egg Production
Most women know that the regularity of their menstrual cycles depends upon the fact that their ovaries produce eggs on a monthly basis. While the menstrual cycle is easy to trackmost women are still very unsure about how ovulation is related to the menstrual cycle because ovulation is an internal event, Many women are confused because of a "chicken and egg" problem.
The Questions
- Which comes first - ovulation ? or menstruation ?
- The reason for the confusion is their reasoning that since the menstrual cycle starts on Day 1 and because ovulation occurs about 14 days later, is it the menstrual cycle which is responsible for ovulation in some way?
- Does a regular menstrual cycle cause regular ovulation?
- And if you have irregular periods, and the doctor gives you medicines to regularise them, does this mean that you have now started ovulating as well ?
The Explanation
Let's try to make sense of the biology behind ovulation and menstruation.
- Normally, one of the ovaries releases a single mature egg every month, and this is called ovulation
- Egg maturation and ovulation is stimulated by two hormones secreted by the pituitary - follicle stimulating hormone (FSH) and luteinizing hormone (LH)
- These two hormones must be produced in appropriate amounts throughout the monthly cycle for normal ovulation to occur
- Every month, at the start of the menstrual cycle, in response to the FSH produced by the pituitary gland, about 30-40 primordial follicles start to grow
- Of these, only one matures to form a large fluid-filled structure, called a Graafian follicle which contains a mature egg, while the others die ( a process called atresia)
- The mature egg is released from the follicle when the follicle ruptures in response to a surge of LH produced by the pituitary
- After ovulation has occured, the follicle from which the egg has been released forms a cystic structure called the corpus luteum
- This is responsible for progesterone production in the second half of the cycle
This means that it is regular ovulation which is responsible for regular menstruation. This is why the rule of thumb is that most women who have regular periods have ovulatory cycles. Women who fail to ovulate or who have abnormal ovulation usually have a disturbance of their menstrual pattern. This may take the form of:
- Complete lack of periods (amenorrhoea)
- Irregular or delayed periods (oligomenorrhoea)
- Occasionally a shortened cycle due to a defect in the second part (luteal phase) of the cycle
Abnormal ovulation
Abnormalities of ovulation ( anovulation) may appear in several ways:
- Menstrual cycles shorter than 21 days or longer than 35 days are often associated with anovulation
- In addition, patients may skip menstrual periods for time intervals of three months or more and this is called oligomenorrhea (infrequent periods)
- If the periods stop entirely, this is called amenorrhea
Many hormonal systems work together to produce regular menstrual periods, and the blood levels of the hormones that make up these systems need to be tested in order to determine the reason for the ovulatory disorders. It's important to note thatwhether can you not ovulate and still have a period is a common question related to menstrual health. If you have concerns about ovulation and menstruation, it's advisable to consult a healthcare professional for personalized guidance and support.
The Tests
The hormone blood tests, which are usually done on the third day of your cycle, test for the levels of the following key reproductive hormones :
- The FSH level: The FSH level gives a good idea of the number of eggs remaining in the ovaries. A high FSH level suggests that the ovary has either failed or has started to fail. If the FSH level is very high (in the menopausal range) then the diagnosis is ovarian failure. If the level is borderline, then some doctors will do a clomiphene stimulated FSH level, which allows for an earlier diagnosis of failing ovaries
On the other hand, a low FSH level suggests hypogonadotropic hypogonadism. This seemingly verbose term simply means that the ovary in these patients is not working properly because of inadequate production of FSH by the pituitary gland. However, in most anovulatory patients, the FSH level will be in the normal range, and this can be reassuring.
- The LH level: This is the other gonadotropin hormone produced by the pituitary; and provides much the same information the FSH level does. Another useful test is the LH:FSH ratio which is normally 1:1.
If, however, the LH level is much higher than the FSH level,this suggests a diagnosis of
polycystic ovarian disease.
If the FSH is much higher than the LH, this suggests poor ovarian reserve.
- The AMH level: This is a new test which is a useful marker for ovarian function. Women with good ovarian reserve will have normal AMH levels. Those with low AMH levels usually have poor ovarian function
- Thyroxine and TSH. These tests for thyroid function. The thyroxine level is high in patients with overactive thyroid glands (hyperthyroidism). In patients with decreased thyroid function (hypothyroidism), the TSH level is increased
- Prolactin: Prolactin is a hormone produced by the pituitary gland that induces lactation or milk formation.. High prolactin levels (hyperprolactinemia) can interfere with ovulation . A milky discharge from the breast nipple , not related to pregnancy or nursing , is called galactorrhea, and this is a telltale symptom of high prolactin levels and needs to be investigated.
If the prolactin level is elevated, the doctor will need to recheck it to confirm it is persistently high. There are many reasons for an elevated prolactin level, including certain drugs as well as stress. In some women, the reason for a high prolactin level can be a small tumour in the pituitary gland.
This is called a prolactinoma or microadenoma, and the doctor may advise you have an X-ray of the skull ( or even a CT scan or MRI scan) to rule out this possibility. However, most infertile women with hyperprolactinemia can be easily treated with a medicine called bromocryptine, which is a dopamine agonist medication .
Another medication which can be used to treat hyperprolactinemia is oral cabergoline, which is usually taken twice a week. Only if the pituitary tumour is very large ( microadenoma) is surgical removal needed, and this is very uncommon.
Ovarian failure
Ovarian failure is a disease in which the ovaries fail to produce eggs. This disease is uncommon, occurring in only about 10% of women whose periods do not occur at all, a condition called amenorrhea (absence of periods). Ovarian failure may be genetic (for example, in girls with Turner's syndrome, a chromosomal disorder) or may be acquired (for example, following radiation or chemotherapy for cancers; surgery to remove the ovaries for treating ovarian cancer or severe endometriosis; autoimmune ovarian failure; or for unexplained reasons.)
Induction of ovulation
The most commonly prescribed medicines for induction of ovulation include the following:
- Clomiphene citrate
- Human menopausal gonadotrophin (HMG)
- Follicle stimulating hormone (FSH)
- HCG (human chorionic gonadotropin)
- Bromocriptine
- GnRH (gonadotropin releasing hormone)
- GnRH analogue.
The Meticulous Approach
Careful monitoring of the response to ovulation induction is the key to therapy - and this usually involves daily ultrasound scans and/or blood tests. It is often a tedious process - which may involve "trial and error" to tailor the therapy to the individual patient's ovulatory response. With the treatments available today, however, correcting ovulatory dysfunction is one of the most rewarding and successful of infertility treatments.
Summary
To understand the biology of conception, it is useful to know the relationship between ovulation and menstruation. Read on to find out why regular ovulation is responsible for regular menstruation.