Inhibin B level is correlated with developing ovarian follicles. The amount of Inhibin B hormone during the start of a new menstrual cycle is directly related to the number and health of small growing follicles. For pregnant women, a high level of Inhibin B results in Down's Syndrome.

Inhibin B Test is performed to evaluate a woman’s ovarian reserve. It is done in addition to the traditional day three FSH and estradiol blood test. Some fertility centers are using these tests, like the AMH (Anti-Mullerian Hormone) and Inhibin B to know how well the woman's ovaries are functioning at that point of time. These tests are generally done as part of an infertility evaluation. (1) Inhibin B is a hormone secreted by specific cells in the ovary. These hormones may sometimes be a sign of Ovarian Cancer or an underdeveloped fetus. These hormones usually regulate menstrual cycles and enable the development of the fetus during pregnancy. However, the Inhibin B blood test is performed to figure the levels of this hormone in women's blood. It is helpful to know how well is the ovarian reserve of women as a measure of their chances of pregnancy. Whereas in pregnant women, it helps to detect aberrations during pregnancy including ovarian cancer.

In this article, we will look at:

1. Inhibin B Clinical Information:

Inhibin is fundamentally heterodimeric protein hormone. It is an important hormone for male and female reproductive health. In females, it is secreted by granulosa cells of the ovary whereas in males Sertoli cells of the testis. (2) Inhibin B is involved in the development of reproductive organs, fertility, pregnancy, and menopause. It also serves as an indicative marker for a variety of body functions and medical conditions whose presence is doubtful in patients. Inhibin is secreted in response to FSH. It ultimately suppresses the production and release of FSH from the pituitary gland.

Reproductive organs are the main source of Inhibin, although it is also present in the prostate, brain, and adrenal glands. There is another sex hormone known as Activin. Activin also increases levels of FSH and Gonadotropin-releasing Hormone (GnRH) production. Inhibin suppresses this increase in FSH and GnRH by blocking the binding of Activin to its receptors. Inhibin is present in the body in two forms:

Inhibin A

Inhibin B

Inhibin A and B levels vary in the blood throughout the menstrual cycle in a woman. Inhibin A levels dominate during the late follicular and luteal phases of a normal menstrual cycle. Inhibin B is at its peak in the early and mid follicular phases and goes down in the late follicular phase. During the late luteal phase, inhibin A levels go down, thus allowing FSH levels to elevate in women. This plays an important role in the biological changes within a menstrual cycle. (3)

In males, only the production of Inhibin B takes place. It is produced in the testis with the assistance of Sertoli cells. Inhibin B hormone production and secretion alter during the development of testis. Whereas Inhibin B increases or decreases the secretion of FSH as per the sperm production process.

2. Roles of Inhibin B:

Inhibin B is basically a hormone produced by certain cells present in ovarian follicles. This hormone after production helps to suppress another hormone called Follicle Stimulating Hormone (FSH). It is secreted by the brain and causes an egg follicle to grow in the ovary. With the increase in the age of the woman, the number of follicles on the ovaries decrease. Along with that the hormones produced by those follicles, like Inhibin B also decrease with the reduction of the number of follicles. This makes Inhibin B test an effective test of a woman’s ovarian reserve or function.



The flow of Inhibin is important for Fertility:

In women, Inhibin B has a different pattern of secretion throughout the menstrual cycle. The decrease in the secretion of Inhibin B hormone decreases the ovarian follicular pool in women and leads to infertility in the concerned individual. Inhibin levels are higher during pregnancy than during a normal menstrual cycle. Inhibin is produced by the placenta and fetal membranes. So, it may be used to diagnose fertility problems and early pregnancy. A mutation in the Inhibin gene is associated with premature ovarian failure. This causes a reduction in Inhibin B activity. So, Inhibin B levels are used to detect Premature Ovarian Failure (POF) and ovarian recovery in women with hypothalamus-associated problems. (4)





Inhibin A and B both can be used to assess the function of the ovaries in patients with Turner syndrome which is a genetic disorder. Total Inhibin B hormone level in the blood is also used in the diagnosis of women with Polycystic Ovary Syndrome (PCOS).

Inhibin Increases Ovarian Health:

The ability of the ovaries to produce egg cells capable of fertilization for a successful pregnancy is called 'ovarian reserve'. Decreased Inhibin B hormone level is seen in women who have been diagnosed with declining ovarian reserve. Women with low levels of Inhibin B hormone also show a reduced response to ovulation stimulation. Hence, they have a decreased chance of becoming pregnant naturally or even with the techniques associated with assisted reproduction. Inhibin boosts the health and development of ovarian follicles. Higher levels of Inhibin B in the follicular fluid also increases the pregnancy rate in the respective women. (5) Inhibin Maintains Male Reproductive Function:

Inhibin B is the active form of Inhibin in men. As Inhibin B levels increase in blood, FSH level decreases. If Inhibin B levels are higher in the blood, it increases the number of Sertoli cells and sperm production in infertile males. Inhibin B Hormone increases Sperm Production:

Inhibin B levels are used to investigate the production of sperms and male reproductive health. In a study conducted in more than 1,800 fertile men, elevated Inhibin B levels in blood were associated with increased sperm count and concentration. (6) Inhibin May Be Involved in Eye Development:

A research was conducted recently in developing mouse eye to find out the role of Inhibin in eye health. Here Inhibin B was seen in the lens and the cells between the lens and optic disc. It was seen in various cell layers of the retina. These results prove that Inhibin may be involved in the development of the retina. In the same way, in the adult rat eye, a subunit of Inhibin known as α-subunit was detected in cells of the retina that respond to light. Inhibin B Reduces Blood Cell Production:

Inhibin B reduces human blood cell production by suppressing the activity of human bone marrow cells. Decreased production of bone marrow and splenic cells was evident in the research after Inhibin injection was given to mice.

3. What is the procedure of Inhibin B Test?

Testing of ovarian reserve is very important because the results can help direct the doctor and plan a treatment routine accordingly. For example, a young woman with an awfully poor ovarian reserve would likely be treated in a detailed manner than a young woman with normal reserve. These are mostly the first group of tests performed, before other, more specific testing. The usage of these medical tests varies from one case to another depending on the respective clinic. It is used in cases where there is an unexpected poor response to the stimulatory medication, and also in couples who have been diagnosed as a case of unexplained infertility. Some centers use it for their egg donors, in order to optimize their donor pool.(7)



No specific preparation is required for Inhibin B Test in most of the cases. However, it is advisable to keep the doctor informed in case someone is allergic to certain products or medications so that accordingly precautions can be taken for the same. The doctor informs the woman of necessary precautions or actions to be taken in that case. Also, for non-pregnant ladies undergoing this test, it is advisable to get the test performed on the third day of their period. Inhibin B test is performed through a simple blood draw like any other basic blood test. Some clinics are able to process the blood on site, where others need to send it out to a specialized lab. Results are available within a span of a day to few days depending on the facilities available at the chosen medical laboratory. The doctor calls the concerned person to discuss the results with them.

The procedure of Inhibin B Test:

First of all blood sample for Inhibin B Test is collected. For blood collection, an elastic band is tied around the upper band to create a pressure that causes the veins to bulge out. A part of the skin of the concerned patient is well cleansed. Then, the needle cap is removed and the needlepoint is held in coalition with the desired vein. The lab technician or respective professional inserts needle into the vein. After that, the syringe plunger is pulled out slowly to collect the required amount of blood. It would be better to put a bandage or cotton on the site where the needle is inserted to cease the bleeding after the blood sample is collected. The wrap around the band is also released. A container, which has an appropriate preservative, is kept ready before the procedure. The collected blood is moved into this container. After the procedure, the needle and syringe are disposed of in a hygienic manner to prevent chances of occurrence of infection.

Evaluation of the Results:

The normal range of Inhibin B hormone depends on the specifications of the lab processing the specimen. A level above 45 pg/ml is considered to be normal. The levels below 45 pg/ml indicate declining ovarian function. These levels of Inhibin B vary depending on where a woman is at during her menstrual cycle. It becomes difficult to interpret the specific levels in premenopausal women even after performing the Inhibin test with the best possible efficacy. If the result of the Inhibin B test is in the normal range, then it signifies a decent overall health status for both pregnant and non-pregnant women. (8)

4. Normal Blood Levels of Inhibin:

In Men:

Inhibin A levels: < 2 pg/ml

Inhibin B levels: Fertile men 138 pg/mL and Infertile men 78 pg/mL

In women



Inhibin A levels:

Premenopausal women: 2-80 pg/ml and Postmenopausal women is < 5 pg/ml

Inhibin B levels:

Premenopausal women: <200 pg/ml and Postmenopausal women is < 15 pg/ml (9)

In pregnant women:

Inhibin A: 1.8- 2.31 ng/mL (week 8); and 2 ng/mL (weeks 8-24) and 24-30 ng/mL by (week 38)

Inhibin B: <12 pg/ml (week 5-16) and 19-31 pg/ml (week 36)

5. Conditions associated with High Inhibin B Levels:

Inhibin Detects Ovarian Cancer:

Ovarian cancer is one of the most widespread cancers in women when the global statistics are taken into consideration. Inhibin plays a role in its expansion. Inhibin B is the chief form of Inhibin secreted by granulosa cell tumors. Blood levels of Inhibin are also raised in women with mucin-producing epithelial cell cancers. (10) Inhibin Predicts Pregnancy Loss:

Inhibin level in blood increase over the course of pregnancy. It stays low during the first and second trimesters and then rises during the third trimester. In the later stages of pregnancy, the fetal placenta becomes the major source of Inhibin. In an unprompted abortion study, a major decrease in maternal blood Inhibin levels is noticed. Thus, Inhibin is been useful in predicting spontaneous abortion and early pregnancy loss. Inhibin A may also predict the survival of the fetus during early pregnancy in women undergoing IVF procedure. An increase in pregnancy loss is seen in women with lower blood Inhibin after IVF procedure. Inhibin acts as a Tumor Marker:

Inhibin is secreted by all granulosa cell tumors of the ovary and can be used as a tumor marker to conclude reaction to therapy. Blood inhibin also increases considerably in breast cancer. However, women having breast cancer that underwent surgery showed a decrease in blood Inhibin levels. It indicates that these tumors may be secreting Inhibin. Inhibin can be also be used as a marker to diagnose breast cancer in postmenopausal women. In these women, inhibin levels are already very low, thus any changes in inhibin levels are useful in the detection of a tumor.(11) Inhibin detects Down Syndrome:

The risk of having a child with Down syndrome is highest among women over 35 years of age. The link between increased blood Inhibin and Down syndrome is seen in various studies. Inhibin B is used in the test performed to predict the risk of Down syndrome. Inhibin detects Preeclampsia:

Preeclampsia is a complicated condition associated with pregnancy. It causes high blood pressure and organ damage after 20 weeks of pregnancy. Inhibin is a marker for the detection of preeclampsia. Blood Inhibin A levels were increased in women with preeclampsia compared to those with a normal pregnancy. Elevated maternal inhibin A levels are also associated with increased severity of preeclampsia.

6. Conditions Associated with low Inhibin Levels:

Inhibin in Ectopic Pregnancy:

The condition of ectopic pregnancy arises when the fertilized egg gets attached to sites other than the uterus. Reduced maternal blood Inhibin level is seen in ectopic pregnancies compared to normal pregnancies. Role of Inhibin in Menopause:

During menopause, ovarian follicles, estrogen, inhibin, and androgen levels reduce, while FSH levels increase. As a result of these changes, the menstrual cycle becomes irregular. Premature Ovarian Failure (POF) and Inhibin B Hormone:

Premature Ovarian Failure is a condition associated with loss of menstruation, increased sex hormone, and infertility in women under the age of 40 years. In such women, Inhibin A and B levels are lower, while FSH is higher. Inhibin monitors Bone Activity:

The replacement and removal of bones take place throughout the body. Bone mass is maintained by this activity of balance between bone formation and bone loss in individuals. (12)

7.Effect of Inhibin B on Fertility in Women:

If the result is within the normal range, the woman has an admirable chance of getting pregnant. As per the result, the doctor suggests basic monitoring or a less persistent treatment plan. If the results are below the low-end values of normal, chances of conception are significantly lower. The doctor may recommend aggressive treatment or even the use of an egg donor to maximize the odds of pregnancy. (13) If a woman is already pregnant, then the fetus is well developed. A low value of Inhibin B indicates lesser chances of contraception for non-pregnant women and a high value in pregnancy may indicate ovarian cancer or an underdeveloped fetus or fetus possessing Down's Syndrome.

8. Inhibin B Test Cost:

The cost of Inhibin B Test varies depending on the lab where the specimen is being processed. In addition, most insurance policies do not cover the cost of this test, so it is important to speak with the fertility center and the lab about potential expenses before the blood is drawn.

9. Lifestyle Factors that help to increase Inhibin B Level:

Losing weight: Inhibin B levels decrease with the increase in weight in males and females. Losing weight can help to increase the inhibin levels in the body. High weight is inversely proportional to Inhibin B level. (14)

Inhibin B levels decrease with the increase in weight in males and females. Losing weight can help to increase the inhibin levels in the body. High weight is inversely proportional to Inhibin B level. (14) Quit smoking: Smoking history is negatively associated with Inhibin B levels in older reproductive-aged women. One should quit smoking at a gradual pace to increase the value of Inhibin B level.

Smoking history is negatively associated with Inhibin B levels in older reproductive-aged women. One should quit smoking at a gradual pace to increase the value of Inhibin B level. Healthy Lifestyle: A healthy lifestyle is key to many issues in the body. Eating healthy and exercising is very helpful for an increase in Inhibin B level in the body.

A healthy lifestyle is key to many issues in the body. Eating healthy and exercising is very helpful for an increase in Inhibin B level in the body. Proper Sleep: Taking proper eight-hour sleep is also helpful to increase the Inhibin B levels. Good sleep is actually very important for a healthy body in different ways.

10. Treatments that Increase Inhibin B Level:

Varicocele Treatment: Varicocele treatment increases blood Inhibin B levels in infertile men.

Human Chorionic Gonadotropin (hCG) treatment: HCG treatment in healthy men significantly increase blood Inhibin B level.

Frequently Asked Questions (FAQs):

1. Why Inhibin B test is helpful to test for ovarian reserve?

Tests for ovarian reserve provide some information regarding how likely it is that a woman's ovaries will produce multiple follicles after hormone stimulation, which in turn is associated with the likelihood of having a baby.

2. Is Inhibin B measurement a good test of ovarian reserve and how?

Inhibin B is levels are directly related to developing ovarian follicles. The amount of inhibin B present in serum during the start of a new menstrual cycle is correlated with the number and health of small growing follicles.

3. How is the Inhibin B test related to pregnancy?

The level of Inhibin B is very low in women with diminished ovarian reserve. If Inhibin B level is below or at the low-end of the normal menstrual cycle range, one has a lower chance of responding well to ovarian stimulation in Assisted Reproductive Technology (ART) protocols than someone with a higher Inhibin B level. A poor response means that the ovary will produce relatively few eggs after hormone stimulation. This will make the chances of one to have fewer embryos after fertilization and a lower chance of getting pregnant.

4. Is the Inhibin B result helpful even if I have a follicle stimulating hormone (FSH) test?

Yes, it is helpful. FSH hormone is an indirect measure of ovarian reserve. Several types of research conducted under the expertise of several experts show that a combination of FSH and Inhibin B measurement can better predict ovarian response and pregnancy outcome than with FSH alone.

5. What should I do to get an Inhibin B test for ovarian reserve?

One should see their physician have blood drawn and send the blood sample to a laboratory offering the Inhibin B test services along with other blood tests.

6. Are there any special issues regarding sample collection?

For proper analysis of Inhibin B results, blood should be drawn on the third day subsequent to the start of a menstrual cycle.

7. How long will it take for the Inhibin B result to be out?

Inhibin B result will be sent to the physician within two to four business days.

8. Will my health insurance pay for my test?

Inhibin B test is introduced recently. So, it is not often covered by health insurance. However, it is best to speak directly to the physician while visiting it for the test. It is also advised to talk to the representative of the healthcare insurance company to find out the regulations linked with the respective test.

Hope you got all the information about the Inhibin B test here. For any query regarding the same, please refer OVO Fertility blogs. OVO Fertility is a healthcare platform that helps childless couples from around the world to get pregnant. The team has helped thousands of couples in fulfilling their dream of becoming parents with the help of the top and result oriented infertility treatments. For a consultation with some of the top infertility experts, feel free to call on the given number: +918268260808.