Irregular Menstrual Cycles

Throughout recorded history, there have been many superstitious beliefs with regards to menstruation.  If a woman does not have a regular, monthly period there are typically a handful of reasons why.  The focus of this blog is to help patients understand the normal menstrual cycle and reasons why they may not have a regular cycle.

A normal menstrual cycle typically occurs every 24-35 days.  It is divided into two phases, the follicular phase when an egg grows inside a follicle and the luteal phase when the follicle becomes a corpus luteum and makes progesterone.  The end of the follicular phase and beginning of the luteal phase is marked by ovulation.  

The menstrual cycle begins with the first day of full flow bleeding, what we call the first day of the last menstrual period or cycle day one.  At the very beginning of the period certain hormone levels in our blood should be low.  Estradiol, a type of estrogen produced by cells in the ovary, and Follicle Stimulating Hormone (F.S.H.) a hormone produced by the brain, are low.  It is this low estradiol from the ovary that signals the brain to start releasing the hormone F.S.H..  The F.S.H. talks to the ovaries and signals a follicle to grow.  Inside each follicle is an egg and surrounding that egg are cells that produce estradiol.  It is important to understand that there are numerous follicles in each ovary, depending on the woman’s age and her genetic make-up.  Normally, only one follicle, with one egg inside, is chosen to grow and ovulate each month.  The other eggs die off at that end of that month.  As the F.S.H. is signaling the follicle to grow and subsequently the egg to mature, the cells surrounding the egg are producing more and more estradiol.  This estradiol is what increases the thickness of the uterine lining.  Once the estradiol reaches a certain threshold level, it signals to the brain to stop making F.S.H. and start making luteinizing hormone (L.H.).  When the brain releases L.H., this tells the ovary to release the egg from the follicle, in other words it tells the egg to ovulate.  Once the egg is released from the follicle (ovulation), what remains of the follicle is called the corpus luteum.  This corpus luteum produces the hormone progesterone.  If the egg is fertilized by sperm, implants into the uterine lining, and starts releasing pregnancy hormone, this corpus luteum continues to make progesterone and you have a pregnancy. If you do not have a pregnancy, the corpus luteum degenerates and there is a drop in progesterone that causes the woman to shed her uterine lining and have a period.  If something with this process is not working, and a woman is not ovulating, she is not going to have a regular period.  If this irregular ovulation is the cause of the patient’s irregular period, it is our job to determine why that is occurring.

When a woman misses more than three menstrual periods over the course of the year, this is not considered normal.  If the woman has no bleeding at all this is called amenorrhea which is classified as either primary, if menstrual periods have not started by age 15, or secondary when periods are absent for more than three to six months in women who have previously had regular periods.  Additionally, a woman may have something called oligomenorrhea which is a term for infrequent menstrual periods, less than six to eight per year.  The causes of irregular periods can be related to conditions that affect the brain, the ovaries, the uterus, or the vagina.  In this article we are going to focus on patients who have had periods before but now do not, secondary amenorrhea, or patients who have irregular periods, oligomenorrhea.  The most common cause of secondary amenorrhea or oligomenorrhea is pregnancy.  Other causes of irregular ovulation resulting in irregular menses include ovarian conditions such as polycystic ovary syndrome (P.C.O.S.) and ovarian insufficiency (early menopause), hypothalamic (a part of the brain that releases hormones) dysfunction,  prolactin (milk producing hormone released from the brain) abnormalities, and thyroid abnormalities.

When a patient comes in presenting with irregular periods, the evaluation starts with a complete medical history and physical examination.  It is important for us to illicit if the patient ever had a normal period, if she has any medical disorders, and if she has a family history of irregular menstrual periods.  We also need to know if the patients have associated symptoms that can help us to make a diagnosis. We ask about breast discharge that we may see if the prolactin is high, hot flashes that can occur if the ovaries do not have many eggs, acne or increased hair growth that we may see in patients with P.C.O.S., changes in weight, diet or exercise that we can see with thryoid disease or with hypothalamic dysfunction.  Next we may perform a physical examination evaluating the patient’s face, neck, breasts and abdomen as well as a pelvic examination.  Depending on findings, we may perform an ultrasound and order blood tests.  Occasionally, a magnetic resonance image (M.R.I.) is performed to determine if there is an abnormality in the brain.  When we identify a cause of the irregular ovulation, the goal is to treat the underlying condition.  How we treat this depends on what the patient’s goal of treatment is. If their goal is to regulate their periods we may treat one way but if their goal is to conceive we may treat another way. Occasionally the treatment is the same.

Of the conditions that cause irregular ovulation and subsequent irregular menstrual cycles that I listed above, the most common one is P.C.O.S..  P.C.O.S. is a chronic condition that causes irregular ovulation, subsequent irregular periods and an excess of androgens (male hormones).  P.C.O.S. has a genetic component and women who are afflicted are more at risk than the general populations for infertility, uterine cancer, diabetes and cardiovascular disease.  The goal in these patients is to try to reestablish normal ovulation in order to try to help these patients conceive. If they do not desire to conceive restoring ovulation is still the goal however if it is not accomplished, the patients are typically placed on hormones to protect their uterine lining.

Hypothalamic dysfunction can sometimes be treated by having patients make lifestyle changes such as gaining weight by either eating more calories or exercising less. Occasionally reducing emotional stress can also help treat this condition. If ovulation does not resume, and these patients desire to conceive, they are typically treated with medications to help them to ovulate.  If they do not desire conception, and their ovulation does not regulate with the above interventions, they may be placed on hormones to protect their bones.

Ovarian failure or insufficiency is when patients stop ovulating because the number of eggs in their ovaries is not as high as it should be for their age.  Having a low number of eggs normally happens around the average age of menopause of 51.  If it happens in women earlier than age 40 this is considered primary ovarian insufficiency, formerly known as premature ovarian failure.  Unfortunately, this condition cannot be cured and to date new eggs cannot yet be regenerated.  In the majority of these patients, fertility medications do not work, and spontaneous conception, donor egg, embyro donation, or adoption are other ways for these patients to build a family.  If patients with this condition do not desire to conceive, they are typically treated with hormones to help prevent them from having symptoms like hot flashes caused by the low estrogen and also to help protect their bones.

If patients have high prolactin as the cause of their irregular ovulation and subsequent irregular menstrual cycles, they can be treated with medications to decrease those levels and similarly this is the case in patients who have thyroid disease as the cause of their irregular ovulation. Lastly, it is important to know that at times irregular menstrual periods can be caused by other things than irregular ovulation such as structural problems like scar tissue in the uterus, called Asherman syndrome, or some sort of blockage of blood in the reproductive organs.

I truly hope this summary has allowed you to better understand how a normal menstrual cycle works, what can cause someone to have an irregular menstrual cycle, and to understand some of the treatments we as reproductive endocrinologists and infertility doctors can employ to help our patients reach their end goal.  Whether that end goal is a regular menstrual cycle or a healthy pregnancy, we are here to help you in your journey!

Kari Sproul von Goeben, M.D.

friends of F.I.R.M.

The Florida Institute for Reproductive Medicine has infertility specialists in Florida and Georgia who have treated infertility patients like Robin. At the FIRM, we help our patients facing infertility feel the same love and support we would give to our own families. To schedule an appointment, call 800-556-5620 or visit

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