Inhibin B testing in the diagnosis of female infertility – the most important information

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The Inhibin B test is one of the laboratory tests performed in the diagnosis of female infertility. Inhibin B plays an important role not only in the female body, its concentration is also important for male fertility. What is Inhibin B and when should it be measured? How to prepare for the test and how does it proceed? How to interpret the test results?

What is Inhibina B?

Inhibin B is a protein hormone that is used to assess a woman’s fertility and to control the process of assisted reproduction. Inhibin B together with the AMH hormone is a hormone that belongs to the basic diagnostic panel when assessing a woman’s fertility. Inhibin B is a hormone produced by granulosa cells located in the ovarian follicle, as well as by the placenta and pituitary gland. The most intense production takes place in the follicular phase of the menstrual cycle. In the early follicular phase, the concentration of inhibin B is the number and quality of follicles.

It is worth noting that the concentration of inhibin B is not always the same and its secretion changes depending on the day of the menstrual cycle. Two moments of intense release of this hormone are characteristic for inhibin B. The increase in inhibin B is noticeable at the very beginning of the menstrual cycle, when FSH levels also rise. Then, until the late follicular phase, the level of inhibin B decreases. A brief increase in inhibin B is observed immediately after the increase in LH in the luteal phase. This short increase is followed by a very rapid decrease in inhibin B.

Inhibin B is a hormone that plays an equally important role in the male body. In men, inhibin B is produced by the Sertoli cells in the testes. Inhibin B in men affects spermatogenesis and the functioning of the testicles. In addition, inhibin B inhibits the FSH hormone in men.

What is worth knowing about hormones important for a woman’s body? Check: Hormones important for women

Inhibin B and fertility problems

Inhibin B, along with the AMH index, is one of the main parameters for the assessment of ovarian reserve. Determination of the concentration of inhibin B allows not only to determine the number and quality of oocytes, but also allows to predict the response to ovarian stimulation in the assisted reproduction procedure. In both women and men, the concentration of inhibin B decreases with age, which in turn is accompanied by an increase in FSH. An interesting fact is that in the case of menopausal women, the concentration of inhibin B is practically undetectable.

Diagnostics indicated in the case of suspected infertility in women, see: Diagnosis of infertility in women – what tests should be performed?

Inhibin B – indications for the examination

The concentration of the inhibin B hormone is most often tested when the woman cannot get pregnant despite strenuous and long-term efforts. The indications for B inhibitor testing include:

1. assessment of the woman’s fertility;
2. planning pregnancy, especially in women who postpone having children for the next few years. Knowing the concentration of inhibin B helps to determine the number of follicles that are able to develop into a mature and valuable egg;
3. diagnostics of pregnancy failures;
4. diagnosing whether an elderly woman has a chance of becoming pregnant;
5. to determine the success of ovarian stimulation to ovulation in the case of assisted reproduction, i.e. in vitro.

Inhibin B testing is also recommended for men. The indications for this test are:

1. assessment of speramtogenesis;
2. determination of the efficiency of the testicle’s seminal tubules;
3. monitoring the treatment of hypogonadotrophic hypogonadism.
4. decision on testicular biopsy or varicocele surgery.

What is worth knowing about a woman’s hormonal economy? Read: Hormones under control, or the hormonal profile for women

Inhibin B testing – do you need to prepare?

The inhibin concentration is determined in an analytical laboratory on the basis of a blood sample. No special preparation is required for the study of inhibin B. There is also no need to go to the test on an empty stomach. However, it is recommended that you drink a glass of water or unsweetened, bitter tea before the test. For women, it is recommended that the level of inhibin B be checked during the follicular phase, preferably on the third day of the menstrual cycle. Depending on the reason for the test, your doctor may choose a different day of the menstrual cycle as the best day to measure your Inhibin B concentration.

How is Inhibin B tested?

Inhibin B testing is most often performed in a laboratory or blood donation point. The test is very short, it takes a few seconds and just takes a blood sample. Blood is drawn for the determination of inhibin B hormone by inserting a fine needle into a venous vessel. The most common puncture is made into the ulnar vein which runs down the elbow. A small amount of blood is needed to measure the concentration.

Inhibin B standards

The actual results of inhibin B depend on the sex of the patient, age and, in the case of women, the phase in which the study was conducted. Usually, the received test result indicates the standards adopted in a given laboratory. It can be estimated that the inhibin B norms for women are:

1. on day 1-2 of the menstrual cycle – 15-70 pg / ml (ng / L)
2. on day 3-5 of the menstrual cycle – 45–120 pg / ml (ng / L)
3. in the late follicular phase – 30-90 pg / ml (ng / L)
4. during ovulation – 80-200 pg / ml (ng / L)
5. in the luteal phase pg / ml (ng / L)
6. during menopause pg / ml (ng / L)

Note that a result above 45 pg / ml on the third day of the menstrual cycle indicates a normal ovarian reserve. In men, the estimated normal values ​​for inhibin B are between 120 and 400 pg / ml.

Interpretation of the Inhibin B result – high and low result

Inhibin B levels that are too high, which are well above the norm, could be a sign of ovarian tumors. Therefore, if the test shows too high a result, you should immediately consult a specialist doctor. Too low levels of inhibin B in women is a sign of a decrease in ovarian reserve – this is natural in the menopause. If a low inhibin B level is found in a woman of childbearing age, it may indicate:

1. premature cessation of ovarian function;
2. Savage syndrome, which is a syndrome of resistant ovaries;
3. hypothalamus dysfunction.

For men, low levels of Inhibin B may be a sign of:

1. azoospermia, i.e. the absence of sperm in the semen;
2. Sertoli’s cell-only complex;
3. damage to the testicle’s seminiferous tubules;
4. germ cell retention;
5. germ cell tumor cell development;
6. Kallmann’s syndrome;
7. Kinefelter syndrome.

Studies related to the Inhibin B study

The diagnosis of female infertility, in which the ovarian reserve is assessed, also includes other tests that must be performed so that the specialist can correctly identify the cause of infertility and undertake appropriate treatment. The following tests should be performed by a woman suspecting that she is infertile:

1. AMH test – is the basic, independent laboratory parameter used in the assessment of a woman’s fertility. The concentration of AMH is measured from the collected blood serum. A low AMH result indicates a decreased ovarian reserve, while a high result may indicate the occurrence of hyperstimulation syndrome. A result of less than 0,7-1 ng / l shows a low ovarian reserve. However, it should be remembered that a single low serum AMH result in women does not mean that she is unable to become pregnant, especially in young women. It’s worth noting that women with low AMH menstruate. And those who had a low level of this parameter throughout their lives may have children.
2. FSH test – when assessing the ovarian reserve, the level of FSH in the blood serum is also determined. This test should be performed on the second or third day of the menstrual cycle. A result above 15 mIU / ml indicates a lowered or low ovarian reserve, and also adversely affects the chance of getting pregnant, the number of properly growing eggs and the proper response of the ovaries to external stimulation. It is difficult to say unequivocally what result is considered alarming. However, it is assumed that results below 12 mIU / ml are normal, while higher results may cause infertility in women. If the FSH test result exceeds 25 mIU / ml, the probability of becoming pregnant is very low.
3. AFC ultrasound is an important test that assesses the number of antral follicles. Anthral follicles are follicles in the ovaries, 2-8 mm in diameter, which are ready to grow under the influence of natural gonadotrophins produced by the pituitary gland. In the course of growth, antral follicles become dominant, and the eggs mature in them. Ovarian infertility diagnosed during the AFC study is a type of infertility associated with disorders at the ovarian level. In ovarian infertility, the biggest problem is poor ovulation, which greatly reduces the chances of getting pregnant. AFC is the basic ultrasound parameter in the assessment of female fertility. This examination is most often performed in the first days of menstruation. This is due to the fact that the number of antral follicles in the ovaries during menstruation is a very sensitive indicator of a patient’s reproductive capacity.

Another important test in the diagnosis of female infertility is the assessment of the ovarian reserve. Find out more about this test and read: Ovarian reserve assessment (AMH) – how to prepare, when to do the test, what does the test look like?

How much does the Inhibin B test cost?

Unfortunately, the Inhibina B test is not reimbursed by the National Health Fund. This means that you have to pay for this test out of your own pocket. The price of the Inhibina B test depends on the city and medical facility where it will be performed. The price of the Inhibina test ranges from PLN 170 to PLN 190.

More information on the costs related to the diagnosis of infertility can be found here: How much do women’s fertility tests cost and where to do them?

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