Have you ever heard of Follicle-Stimulating Hormone , or FSH for short? You may find the name a bit scientific. However, it is a hormone that is very important for our body's sexual development and ability to have children. It acts like a little messenger in our body. Let's talk about it in a little more detail, shall we?
What is FSH?
Okay, so let's see what exactly FSH is. FSH, which stands for Follicle-Stimulating Hormone, is a special chemical that is made by a little gland at the base of your brain, called the pituitary gland , and released into the body. This is a hormone . Hormones are like messengers in our bodies. They travel through the bloodstream and tell our organs, muscles, and other tissues what to do and when to do it.
Now, when you hear the word 'follicle-stimulating', some people might think that this is something related to hair. Because the word follicle is also used with hair. But actually, this FSH hormone does not directly affect your hair follicles or hair growth. Hair growth is affected by a separate group of hormones called androgens . FSH gets its name from the small sacs in the ovaries of girls, that is, the fluid-filled sacs containing egg cells, which we call ovarian follicles , because this hormone affects them. Simply put, FSH is an important hormone that comes from the pituitary gland that helps in our sexual development and making children. It affects the ovaries in girls and the testicles in boys.
What happens with FSH?
This amazing hormone called FSH performs many important functions in our bodies at different ages and in different ways. Let's take a look at each of them separately.
How FSH affects a baby in the womb
Did you know that this FSH hormone starts working even before we are born? When a mother has a baby in her womb, during the second and third trimesters of pregnancy (that is, from 13 weeks to 26 weeks, and from 27 weeks to the end of pregnancy), the baby's pituitary gland releases FSH and another important hormone , Luteinizing Hormone (LH) . These hormone levels peak around mid-pregnancy. That is when the baby's first ovarian follicle (if it is a girl) or the sperm-producing tubes ( seminiferous tubules - if it is a boy) mature. Imagine, these hormones start working in our bodies from such a young age.
The role of FSH during puberty
During childhood, FSH levels are usually low. But as a child approaches puberty (usually between the ages of 10 and 14), a part of the brain called the hypothalamus produces a hormone called gonadotropin-releasing hormone (GnRH) . GnRH stimulates the production of FSH and LH. This is when sexual maturation and growth changes begin.
- In boys , FSH and LH work together to stimulate their testicles to produce a hormone called testosterone . This testosterone is what causes the physical changes in boys during puberty (such as facial hair, chest hair, and a deepening voice) and also causes sperm production.
- In girls , FSH and LH work together to stimulate their ovaries to produce a hormone called estrogen . This estrogen is what causes the signs of puberty, such as breast development and the start of menstruation.
How is FSH important for women who are menstruating?
In women who have monthly periods, the main function of FSH is to help regulate the menstrual cycle. Specifically, FSH stimulates the follicles in the ovaries to grow and prepare eggs for ovulation . As these follicles grow, they begin to release the hormones estrogen and, to some extent , progesterone into the blood.
Ovulation is a phase of the menstrual cycle. In a normal 28-day menstrual cycle, this occurs around day 14. Simply put, it is the release of an egg (ovum) from an ovary.
Each month, between days 6 and 14 of the menstrual cycle, FSH stimulates the development of several follicles in one ovary. However, between days 10 and 14, only one of these developing follicles develops into a fully mature egg. Around day 14 of the menstrual cycle, a sudden surge in the hormone LH causes this mature follicle to burst and release an egg (this is called ovulation ).
After ovulation, the ruptured follicle becomes a corpus luteum (a temporary hormone-producing gland). This produces more progesterone. Progesterone stops the release of FSH and helps prepare the lining of the uterus for pregnancy.
The released egg travels for about five days through the Fallopian tube to the uterus. If it is successfully fertilized by a sperm during this time, pregnancy occurs. If fertilization does not occur, the corpus luteum breaks down at the end of the menstrual cycle. Progesterone production then decreases, FSH levels start to rise again, and the next menstrual cycle begins – which is when you have your period.
What FSH does to men
In men, FSH mainly stimulates sperm production . LH stimulates the production of testosterone in the testicles, and FSH works with testosterone to keep sperm production going.
How is FSH production controlled?
Now you may be wondering how this FSH is controlled so precisely. This is done by a very complex, but amazingly working system. We call it the Hypothalamic-Pituitary-Gonadal axis . It is like a call center. A call comes from one place, the next place responds to it, and depending on that response, a different call comes from the first place. If any of the parts of this system in the brain (hypothalamus), the pituitary gland, or the sex glands (ovaries or gonads) are not working properly, the hormone levels involved in this system can be abnormal.
First, a part of your brain called the hypothalamus releases gonadotropin-releasing hormone (GnRH) . This GnRH stimulates the pituitary gland to release FSH and LH (both of which are also called gonadotropins). The hypothalamus releases GnRH in small amounts, called pulses . When these pulses come less frequently, more FSH is produced, and when they come more frequently, more LH is produced. Isn't that amazing?
Then, the released FSH and LH travel through the bloodstream and bind to special receptors in the testicles or ovaries. That's how FSH and LH work together to control the function of the testicles and ovaries.
In response, hormones released from the testes or ovaries control the amount of GnRH produced by the hypothalamus. This cycle continues. However, different amounts of some hormones in this system affect the release of other hormones differently.
For example, the female hormone estrogen has several effects on FSH release. Long-term exposure to estrogen reduces FSH release. However, when estrogen levels rise as they normally do before ovulation, it stimulates the pituitary gland to increase gonadotropin (FSH and LH) levels. Progesterone reduces the frequency of GnRH release from the hypothalamus, but increases the responsiveness of gonadotropins to GnRH.
In men, a hormone called Inhibin B, released from cells in the testicles, stops the production of FSH as part of this feedback loop.
So, again, if there is any disruption or problem in this hormone release chain, it will cause a decrease in sex hormones. This will interfere with normal sexual development in children and will also interfere with the normal functioning of the testicles or ovaries in adults.
What should normal FSH levels be like?
Normal FSH levels vary depending on your age and your sex (i.e. whether you are female or male). Another thing to keep in mind is that these normal FSH ranges can vary slightly from one lab to another. So, always check the lab's normal range on your blood test report . If you have any questions about your results, be sure to ask your doctor.
Normal FSH levels in men
Normal FSH levels in men are as follows (units: mIU/mL - milli-international units per milliliter):
- Before puberty: 0 to 5.0 mIU/mL.
- During puberty: 0.3 to 10.0 mIU/mL.
- Adult: 1.5 to 12.4 mIU/mL.
Normal FSH levels in women
Normal FSH levels in women are as follows (unit: mIU/mL ):
- Before puberty: 0 to 4.0 mIU/mL.
- During puberty: 0.3 to 10.0 mIU/mL.
- After puberty (before menopause): 4.7 to 21.5 mIU/mL.
- After menopause : 25.8 to 134.8 mIU/mL.
How do you check the FSH level of someone trying to get pregnant?
When looking at FSH levels for fertility, the timing of the test is very important . FSH levels change throughout your menstrual cycle. For fertility testing, the FSH blood test is usually done on Day 3 of your menstrual cycle ( Day 1 is the day you start your period).
One study showed that women with FSH levels less than 15 mIU/mL on day 3 of their menstrual cycle were more likely to conceive through IVF (In Vitro Fertilization) than those with FSH levels between 15 mIU/mL and 24.9 mIU/mL. Women with FSH levels greater than 25 mIU/mL had even lower rates of pregnancy after IVF attempts.
But remember, there are many other factors that affect your ability to have children – your FSH level is not the only deciding factor . If you have any questions about your ability to have children or about getting pregnant, ask your doctor or a fertility specialist .
What can happen if FSH levels increase?
Most of the time, higher than normal FSH levels mean there is a problem with either the ovaries or testicles (that is, the gonads ).
Imagine, if your gonads are unable to produce enough estrogen, testosterone, and/or inhibin, the feedback loop from the pituitary gland to produce FSH is disrupted. Then, levels of both FSH and LH increase. This condition is called hypergonadotropic-hypogonadism or primary hypogonadism . This is related to Primary Ovarian Insufficiency (POI) or testicular failure .
Primary hypogonadism can be congenital or acquired due to other medical conditions.
The types of primary congenital hypogonadism are:
- Klinefelter syndrome in males.
- Turner syndrome in females.
- Androgen insensitivity syndrome .
- Some enzyme deficiencies (these are very rare).
The following can cause later onset primary hypogonadism:
- Things that are toxic to the gonads, for example radiation therapy or chemotherapy .
- Damage or injury to the ovaries or testicles.
- Decrease in sex hormones with age.
- Some autoimmune conditions .
- Infections like mumps .
Very rarely, problems with a woman's pituitary gland can cause high FSH levels. This can disrupt the normal feedback loop and sometimes lead to a condition called ovarian hyperstimulation syndrome . This can cause the ovaries to swell and cause dangerous fluid to build up in the abdomen.
FSH levels naturally increase as women approach and during menopause . This is normal.
In children, if FSH and LH levels are higher than expected for their age – along with the early appearance of secondary sexual characteristics – it is a sign of precocious puberty . This is most common in girls. Precocious puberty is defined as puberty occurring before the age of 9 for girls and 10 for boys.
What can happen if FSH levels decrease?
Lower than normal levels of FSH usually result in failure to fully develop during puberty. In adults, the ovaries or testicles may not function properly, which can lead to infertility . This condition is called hypogonadotropic-hypogonadism . It is usually caused by problems with your pituitary gland or hypothalamus.
How pituitary gland problems can cause low FSH
Hypopituitarism is a very rare condition in which your pituitary gland produces too little of one, several, or all of the hormones. So, hypopituitarism can cause low FSH levels.
Although it is rare, many conditions and causes can cause hypopituitarism. In general, these three main causes can cause hypopituitarism:
- Something is putting pressure on your pituitary gland or hypothalamus.
- Damage to your pituitary gland or hypothalamus.
- You have a rare condition that can cause hypopituitarism.
One common cause of primary hypopituitarism is a pituitary adenoma . This is a benign tumor that develops in the pituitary gland. If the adenoma is large enough or continues to grow, it can put pressure on the pituitary gland or block blood flow to it.
How hypothalamic problems can cause low FSH
Kallmann syndrome is an inherited condition. In this condition, your hypothalamus does not produce enough gonadotropin-releasing hormone (GnRH). When there is not enough GnRH, FSH levels decrease, and so do sex hormone levels. If left untreated, a person with Kallmann syndrome will not reach puberty and will not be able to biologically father children.
What are the symptoms of FSH level abnormalities?
Unless FSH levels in children are abnormally high and cause early puberty, FSH levels, whether high or low, usually indicate a condition called hypogonadism . Hypogonadism is when the gonads, either the testicles or ovaries, produce little or no sex hormones.
When FSH levels are low due to a problem with your hypothalamus or pituitary gland, it directly leads to hypogonadism. However, higher than normal FSH levels can be a sign or side effect of hypogonadism caused by a problem with your gonads.
This is because when the gonads are producing less sex hormones (often due to damage), your pituitary gland tries to stimulate them to produce more sex hormones. This is why it releases more FSH. At this time, FSH usually has no effect, because there is something wrong with the tissues of the gonads that make sex hormones.
The symptoms of hypogonadism vary depending on your age and whether you are male or female.
Symptoms of hypogonadism in newborns may include:
- Having an abnormally small penis ( micropenis ).
- Undescended testicles ( Cryptorchidism ).
Symptoms of hypogonadism in children may include:
- Girls' breasts do not develop during puberty.
- Absence or delay of monthly menstruation ( amenorrhea ).
- Boys' testicles not getting bigger.
- Lack of a sudden growth spurt during puberty.
Symptoms of hypogonadism in men:
- Decreased sexual desire.
- Fatigue .
- Infertility , often due to a lack of sperm ( Azoospermia ).
- Erectile dysfunction .
- Breast enlargement ( gynecomastia ).
- Decreased muscle strength.
- Loss of facial or body hair.
Symptoms of hypogonadism in women:
- Decreased sexual desire.
- Fatigue.
- Infertility, often due to ovulation problems.
- Hot flashes .
- Irregular menstruation or complete cessation of menstruation.
- Hair loss in the private area.
How to check FSH levels?
A doctor can check your FSH levels with a blood test . This involves taking a blood sample from a vein in your arm using a needle. It's very simple.
Doctors may order FSH blood tests for a variety of reasons. They may also order other hormone blood tests at the same time, either to diagnose or rule out certain medical conditions. For example:
- Luteinizing hormone (LH).
- Testosterone.
- Estradiol and/or progesterone.
In general, these tests help with things like:
- Find out the reason for not having children.
- Diagnose conditions associated with dysfunction of the ovaries or testicles.
- Help diagnose conditions in the pituitary gland or hypothalamus that may affect FSH production.
To be more specific, for women, FSH blood tests can reveal the following information:
- Look up irregular periods .
- Predict whether they are approaching or have already entered menopause.
In men, FSH blood tests can help determine the cause of low sperm count .
Doctors use FSH and LH blood tests to determine whether children are experiencing delayed or early puberty .
When should you talk to a doctor about FSH?
If you feel like you have symptoms of hypogonadism, be sure to see your doctor .
If your child seems to be going through puberty earlier or later than expected, see their doctor. They may do some simple blood tests to see if there's anything wrong with their FSH levels.
If you're having trouble getting pregnant, talk to your doctor or a fertility specialist. While there are many reasons for infertility, your FSH levels may be one of them.
In summary
Okay, so the most important thing you need to remember from what we've talked about is that follicle-stimulating hormone (FSH) is an important hormone that has a very powerful effect on our sexual development and fertility . Since FSH is part of a complex system that works in conjunction with many other hormones and glands, it's not uncommon for FSH levels to be abnormal.
If you or your child have any symptoms related to sexual development or fertility, please see your doctor and discuss them. They are here to help. Never try to be alone, it is always wise to seek medical advice.
` Follicle-stimulating hormone, FSH, hormones, pituitary gland, reproductive health, puberty, menstrual cycle, infertility, hypogonadism, LH, GnRH
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