Surprisingly, all fetuses have an undifferentiated reproductive tract at the beginning of fetal development, meaning that it can become either the male (Wolffian) or female (Mullerian) reproductive tract. Fetal hormones determine which type of duct will form.
The Mullerian duct is the default reproductive tract. This means that, if no hormones were produced, the Mullerian duct would form. However, fetal males produce a lot of the hormones AMH (anti-Mullerian hormone) and testosterone. Anti-Mullerian hormone prevents the Mullerian tract from forming, while testosterone drives the formation of the Wolffian ducts. Thus, male fetuses typically develop Wolffian ducts, which give rise to reproductive structures such as the epididymis and vas deferens. On the other hand, fetal females do not produce a lot of AMH and testosterone. As a result, the Mullerian duct forms instead of the Wolffian ducts. The Mullerian ducts give rise to reproductive structures such as the Fallopian tubes.
Even cell division is known as mitosis. During mitosis, a cell duplicates its DNA so that the new cell has the same number and type of DNA as the original cell (these are known as diploid cells).
Sperm and egg cells undergo meiosis, which involves two separate cell divisions that produce cells with only half of the original amount of DNA (known as haploid cells). This is important because, when a sperm cell fertilizes an egg cell, it deposits its DNA into the egg. The result is an embryo with 2 sets of DNA (one from the egg and one from the sperm). If eggs and sperm had the same amount of DNA as other cells in our bodies, the embryo would have too much DNA. However, once an embryo is formed, its cells begin to divide via mitosis, or even cell division. Meiosis only occurs in egg and sperm cells.
Unlike males, who create sperm throughout their lives, females are born with all of the eggs that they will have. During early fetal development (around 10 weeks), the egg cells actually undergo mitosis to make all of these eggs. These eggs eventually begin to undergo meiosis before the fetal female is even born, but they freeze in the middle of the first division.
Beginning during fetal development and continuing throughout her life, the number of eggs in a woman’s ovaries declines until menopause occurs (or earlier if there is some sort of insult, such as chemotherapy or radiation). Ovarian reserve refers to the number of eggs that remain in a woman’s ovaries at any point in time.
Reproductive hormones begin being produced during fetal development and are essential for normal reproductive function. In fetal females, the amounts of FSH (follicle stimulating hormone) and LH (luteinizing hormone) are quite high, but they decline when the baby is born. There is a small peak in these reproductive hormones up to 6 months after the baby girl is born. As a result, newborns can sometimes have vaginal bleeding as her hormone levels fall.
During the prepubertal years, the levels of reproductive hormones are very low. But when puberty occurs, the levels of these hormones begin to increase again. As a result of the increased FSH and LH production, the ovaries begin to produce the hormone estrogen and other hormones.
There are two main control centers for puberty:
The first signs of female puberty are the formation of breast buds and pubic hair, a growth spurt, and menarche (the first menstrual cycle). Surprisingly, the formation of pubic hair is caused by the adrenal glands, so it’s possible to see pubic hair formation even before menstruation begins. Later stages of puberty include the formation of secondary adult sex characteristics.
The signs of male puberty are graded on the Tanner scale (1-5). The first signs include growth of the male genitalia and pubic hair, followed by a growth spurt and the production of sperm.
Follicles are sac-like structures that house the eggs inside the female ovaries and produce the hormone estrogen. Each menstrual cycle, the brain produces a high volume of FSH and LH. This causes some of the eggs inside their follicles in the ovaries to begin to mature (resume meiosis). As the eggs mature, the sizes of their follicles grow. However, only one egg ends up maturing each cycle (or two in the case of twins) while the others degenerate. This egg sits inside a large follicle, known as the dominant follicle, and is ovulated in that particular menstrual cycle. Ovulation occurs after a surge of LH is produced by the brain, and it refers to the expulsion of the egg from its follicle and the ovary. The egg is picked up by cilia (hair-like projections) in the Fallopian tube and begins to move down the Fallopian tube, where fertilization can occur, on its pathway to the uterus (which can take roughly 5 days).
Once the egg is expelled, the dominant follicle undergoes a stem-cell like change and becomes a hormone producing gland known as the corpus luteum (yellow body). The corpus luteum is responsible for producing a large amount of progesterone, which travels to the uterus and causes its inner lining, the endometrium, to thicken in preparation for embryo implantation. If implantation does occur, cells in the placenta begin to produce the hormone beta hCG (human chorionic gonadotropin), which “rescues” the corpus luteum (and causes another menstrual cycle to not occur). As a result, the corpus luteum will continue to produce progesterone for a few weeks until cells in the placenta known as syncytiotrophoblast cells produce enough progesterone to sustain the pregnancy. At this point, the placenta will take over progesterone production and the corpus luteum will degenerate. If implantation does not occur, the corpus luteum will undergo atresia (degenerate), no more progesterone will be produced, and another menstrual cycle will begin. The reproductive hormone levels are very high throughout the pregnancy, but they drop around the time of birth, or parturition, under the control of the fetus.
As an embryo moves down the Fallopian tube and into the uterus, there is a communication between the endometrium and the embryo that allows the embryo to implant. Since the embryo contains genetic material from the sperm, which is foreign to the female body, it’s important that the endometrium does not reject the embryo.
Age is the primary determinant of fertility. Optimal fertility occurs in a woman’s 20s and begins to decline in her 30s. Around 45, a woman’s periods begin becoming more irregular and then menopause occurs. However, menopause cannot be diagnosed for 12 months. Estrogen levels begin to decline as a woman approaches menopause. The symptoms of menopause consist of hot flashes, night sweats, and vaginal dryness, among others. Some women experience many symptoms of menopause, while others experience few to no symptoms.
Yes! The ovaries also make the hormone testosterone, which can be converted to estrogen in the body. In a typical ovulatory cycle, there is a collaboration between two types of cells in the growing follicle: one type of cell makes the precursor hormone, which is an androgen. The second cell has the machinery to convert the androgens to estrogen.
The ovaries of women who have gone through menopause still produce some testosterone, which can be converted to estrogen in other cells in their bodies. So, the ovaries are very important, even after menopause!
Studies have shown increased mortality (death) rates in women who have their ovaries removed. This was even more prevalent when younger women had their ovaries removed. As a result of these studies, less women are having their ovaries removed when they undergo a hysterectomy (removal of the uterus) unless the ovaries need to be removed for other reasons.
Ovarian cancer is often silent. In other words, the early stages are difficult and subtle, so many women are not diagnosed until the later stages. A lot of research is being done to find ways to diagnose ovarian cancer early since it is very aggressive.
Ovarian cancer is so aggressive because there is no natural barrier for the cancer cells. So, if the cancer cells begin in one or both of the ovaries, they can quickly migrate (metastasize) to the uterus, abdominal organs and, in late stages, the lungs and chest. Most cases of ovarian cancer are not diagnosed until they are at stage 3.
Studies over the past 5-10 years have actually found that many cases of ovarian cancer begin in the Fallopian tubes rather than the ovaries. These cancer cells migrate toward the ovary and then seed (implant on) the ovary or ovaries. Further, the incidence of ovarian cancer is decreased when the Fallopian tubes are removed.
For these reasons, it’s important to keep track of your menstrual cycles. If your cycles are irregular, it could be an indication of an underlying condition.
When the ovaries stop working on their own at a younger age, it’s also associated with increased morbidity and mortality. It’s important for patients to get an early diagnosis before the ovaries begin to fail, but unfortunately it can be difficult to notice the symptoms. For example, women on birth control may not notice any changes to their menstrual cycles. One focus at Pelex is performing preventive medicine for reproductive endocrinology.
Yes, primarily through lifestyle changes. Try to maintain a healthy diet and exercise routine, get enough sleep, and avoid stress, alcohol, tobacco, and recreational drugs. Some supplements have also been shown to help with male factor infertility.
PMS refers to the symptoms one experiences right before a menstrual cycle. It is likely caused by the changes in hormone levels before the menstrual cycle, particularly progesterone. It can be hard to pinpoint the exact cause, but sometimes medications can be prescribed to alleviate the symptoms.
IVF hormones and treatment don’t change what the underlying risk is. But, if you are infertile and need hormones and IVF, you have an increased risk of some medical problems. It’s been found that infertility in general actually increases morbidity and mortality. People who are infertile have more health problems than people who are fertile.
Birth controls are good and bad. For example, birth control pills are an important tool for patients with PCOS because extra estrogen can balance out the high levels of androgens. Further, if you are not ovulating each month, the progesterone in the birth control pills is critical for preventing endometrial cancer. However, for patients with low estrogen levels, birth control pills are not as beneficial and can have negative impacts on their bones. Birth control can also mask infertility conditions, such as premature ovarian failure (which is not caused by birth control pills).
Surgical removal of the endometrial-like tissue has become very advanced in the last few years. However, the surgery can still have negative effects on the ovarian function.
Currently, there are no effective and reversible forms of male birth control. However, there are permanent forms, such as vasectomies.
The average age for menopause in the US is 51.5 years old. However, some women do have menstrual cycles through their 50s and it is normal, assuming that the cycles are still regular and there are no underlying medical problems.
No, but it does help to see if there is a recurrence of ovarian cancer. The best way to screen for ovarian cancer is to do ultrasounds for ovarian cysts. However, this is not routinely performed since it is not seen as a necessary treatment.
Unfortunately, these pregnancies are nonviable and are one of the leading causes of maternal death in the first trimester. The most important thing is to go to a doctor as soon as you know that you are pregnant for early detection and intervention of an ectopic pregnancy. A doctor can help to ensure that your blood levels are rising appropriately. It’s possible to get pregnant after an ectopic pregnancy, but it depends on how much damage is done during the pregnancy. If one tube needs to be removed, it’s still possible to achieve fertilization using the other Fallopian tube. If both tubes are removed, IVF can help to bypass the Fallopian tubes to achieve a pregnancy. In severe cases, the damage caused by an ectopic pregnancy can cause uterine damage, as well. In these cases, healthy pregnancies are unlikely to occur. Ectopic pregnancies are more common with lower ovarian reserve.
Yes. But it’s important to lessen the dosages as women age, and it depends a lot on the patient’s medical history.
It depends. If you’ve always had regular cycles, you will likely have regular cycles shortly after you stop the birth control. If your cycles were not regular, they will likely not be regular afterward or may take more time to regulate after you stop the birth control.
PCOS is a syndrome, so it’s diagnosed through its primary symptoms. These include irregular periods, increased androgens (determined through a blood test, acne, or facial hair growth), and polycystic-appearing ovaries on ultrasound. You need to have 2 of these 3 symptoms to be diagnosed with PCOS. In reality, PCOS is vague and difficult to study. But there are subtypes of patients with PCOS. For example, some have insulin resistance, while some have irregular periods, and some have no symptoms at all.
Yes. IVF can override a lot of the natural steps involved in getting pregnant that endometriosis can affect. In fact, it’s been found that endometriosis shows progesterone resistance, meaning that it is not very responsive to progesterone. When women are preparing for an embryo transfer, it’s important that they have high levels of progesterone to thicken their uterine lining. The