Hormone Testing and Interpretation for Male Infertility
Optimizing the Hormonal Environment to maximize sperm quality
Hormones play an extremely important role in the male fertility process. GnRH (gonadotropin-releasing hormone) is a hormone that stimulates the pituitary gland, which is the brain’s hormonal control center. The pituitary gland in turn releases FSH (follicle-stimulating hormone), which drives the testicles to make sperm. The pituitary also secretes LH (luteinizing hormone), which causes the testicles to produce testosterone, which is needed in high levels to promote adequate sperm production. A deficiency in any of these hormones can cause significant problems with sperm production and quality. In addition, some fertility-related issues (such as normal erection and ejaculatory function) also rely on adequate hormone levels and balance.
Who Should Have Hormone Testing?
Hormone problems are a relatively common cause of male fertility problems. Studies have clearly shown high rates of hypogonadism in men undergoing evaluations for infertility. Very low testosterone levels (<300ng/dL) have been found in 44.6% of men with decreased sperm counts. This hypogonadism can negatively impact a man’s fertility potential and sexual function as well as increase their risk of general health problems including diabetes, obesity, hyperlipidemia, coronary vascular disease, osteoporosis, and depression. [Greenburg DR. Urol 2023]
It is recommended that men get hormone testing if they have any of the following problems:
1) Abnormal fertility testing (such as abnormal semen analysis results or abnormal sperm DNA testing results)
2) Symptoms of low testosterone:
• Erectile dysfunction
• Decreased libido (sex drive)
• Fatigue, decreased energy
• Depressed mood, decrease in feelings of well-being
• Decreased intensity of orgasm
• Difficulty achieving orgasm
• Decreased ejaculate volume
• Accumulation of fat around the abdomen
• Decreased muscle mass
• Osteoporosis/osteopenia (decreased bone density)
Deciding Which Hormone Tests to Order and How to Get Them Done
Any man with symptoms of low testosterone should have the following four hormone tests:
1. Total testosterone
2. Estradiol
3. Follicle stimulating hormone (FSH)
4. Luteinizing hormone (LH)
Other Hormone Tests
There are a number of other fertility-related hormones that I do not routinely recommend testing for but which are checked in particular circumstances. These would include:
1) Thyroid-stimulating hormone (TSH). I recommend ordering a TSH only for men who have symptoms that may indicate possible thyroid-related problems.
a) Hypothyroidism: fatigue, cold intolerance, sleepiness, weight gain, muscle aches, abnormally
slow heart rate, constipation, dry skin, brittle hair, decreased concentration/memory
b) Hyperthyroidism: nervousness, fatigue, weakness, palpitations, heat intolerance, excessive
sweating, diarrhea, insomnia, poor concentration, weight loss, abnormally fast heart rate,
warm and moist skin
2) Prolactin. A brain hormone which can decrease gonadotropin (LH and FSH) secretion and thereby lower testosterone levels. I order this only if the initial total testosterone levels are under 300 ng/dL.
3) Inhibin B. A more direct testicular marker of sperm production. This test is ordered only for very particular circumstances, such as in men who have had a prior vasectomy and who are also on testosterone replacement therapy.
Recommendations on Performing Hormone Testing
Many of the medications that we have for male infertility (such as clomiphene, anastrazole, etc.) are used to treat hormonal problems. Medical care providers who are not very familiar with male infertility problems often prescribe these hormonal medications just to try out a treatment, without any identified hormonal problem that they are trying to correct (this is called "emperic" treatment). Studies have shown that this type of empiric hormonal treatment is not particularly effective. A better way of evaluating and managing hormonal problems in men is to always try to get baseline hormone levels drawn before any hormonal medications have been started. Then if any specific abnormalities are identified (such as a low testosterone or high estradiol level), then the proper medication can be chosen to address that problem. If a hormonal medication is started, then follow-up testing should be performed about 2-4 weeks later to make sure that the body is responding to the medication appropriately, and the treatment regimen can then be modified accordingly if needed.
Timing of Hormone Testing
Most hormone testing (estradiol, FSH, LH, TSH, prolactin) can be done at any time of day, but blood for testosterone (and inhibin B) levels should be drawn between 7:00 and 10:00 a.m., as this is when most men have their highest blood levels of testosterone. Men who consistently work night shifts can have their testosterone levels drawn at their normal wake-up times. Men who inconsistently work night shifts should try to get their testosterone levels drawn between 7:00 and 10:00 a.m. on a day off from work. Fasting is not required for standard fertility hormonal testing.
Repeat Testing for Abnormal Initial Results
Many fertility experts will repeat blood hormone testing such as testosterone levels if the results are abnormal initially. They do this for a good reason, since blood hormone levels are known to fluctuate to some degree on a day-to-day basis. For example, testosterone levels generally vary by 10 percent in the same individual over the course of a week. LH levels have much higher levels of variation, while FSH tends to show much less variation over time.
I think that repeating low testosterone levels is a completely valid way to approach hormone testing in men. However, when I have a man who has a low testosterone level on initial testing, I typically do not repeat the test before starting treatment. My rationale is that if a man has a low baseline testosterone at initial testing, then even if it is normal on repeat testing, that man’s testosterone levels are likely borderline at best, and he may benefit from hormonal therapy. One thing to keep in mind is that every so often lab errors do occur. So if an unexpected result comes back (such as testosterone levels going down after therapy has started, or blood hormone levels that do not match a man’s clinical symptoms), then I do recommend repeating the blood test before making a definitive decision about treatment.
My problem with routine repeat testing of problems such as low testosterone is the question of how to proceed if the repeat testosterone level is now within the normal range. Which of the two results most accurately reflects the hormonal environment of the man? Do you get a third testosterone test as a “tie-breaker”? That is a lot of lab cost, needle sticks, and time to spend before you even begin to start any treatment (which if started is going to take at least ten weeks to show maximal effectiveness).
Notes on Pricing
Fertility testing and treatments are sometimes but not always covered by insurance. The good news about hormone testing is that problems such as low testosterone can affect a man’s general health and not just his fertility. Therefore, non-fertility-related diagnosis codes, which have a higher chance of being covered by insurance even in states without mandated fertility-related insurance coverage, can often be used for hormone testing. The codes I recommend using for hormonal testing are E29.1 (testicular hypogonadism) and E29.9 (testicular dysfunction).
For more detailed information, see the "Hormone Testing Costs" section of this website.
Interpreting male fertility Hormone Test Results
Normal Values and Reference Range
It is very important to remember that normal values are not the range of values typically listed to the right of your test results on the official lab report. These printed values are the “reference” values—the range into which 95 percent of patients tested in that particular lab fall. This reference range can often include lab values that are well outside of the actual normal range for that hormone. For example, FSH reference ranges printed on lab reports often say something like “1.1–15.0 MIU/mL” when in reality an FSH of more than 7.6 MIU/mL is considered abnormally high from a clinical standpoint. So do not use the printed reference ranges on lab reports as a definition of what is actually normal for that lab value. Instead, refer to the values indicated on this website or discuss your results with your own fertility provider.
Managing Abnormal Hormone Test Results
An abnormal hormone environment is a fairly common cause of male infertility problems. If any hormone abnormalities are uncovered during testing, the management of these issues can be reviewed in "Hormone Abnormalities" in the Sperm Boot Camp section of this website.
Testosterone and Male infertility
Androgens are male sex hormones. There are a number of substances that have male hormonal properties (including anabolic steroids, prohormones, DHEA, etc.), but testosterone is the body’s primary androgen.
Androgens are important for the bodily characteristics we associate with being male (e.g., deeper voice, beard growth), maintaining good sperm production, and facilitating normal sexual function. Normally in men, most testosterone is produced by the Leydig cells within the testicles in response to LH secreted by the pituitary gland. The adrenal glands (which sit above the kidneys) also produce androgenic hormones, but these make up less than 10 percent of the total androgens in the body.
When you get a blood test to measure testosterone levels, the test result reflects the amount of testosterone that is circulating in the bloodstream. Since under normal circumstances most of the testosterone in the body is made by the testicles, the concentration of testosterone in the testicles is about a hundred times higher here than in bloodstream. These very high testosterone levels within the testicles are necessary for optimal sperm production. So in terms of sperm production, the testicular testosterone levels are what we are interested in. Unfortunately, there is no good way to directly monitor intratesticular testosterone levels without needle aspirations of testicular tissue (which would be very uncomfortable to say the least, and are not clinically available regardless).
Of note, the pituitary gland manages the production of testosterone through feedback loops that monitor testosterone levels which then control the release of LH to increase or decrease testicular testosterone production. It is important to remember that the pituitary gland is monitoring blood levels of testosterone, not the intratesticular testosterone concentrations. Normally this works fine since high blood levels of testosterone usually correlate well with high intratesticular levels. However, in some circumstances the blood testosterone levels are not a good reflection of the testosterone levels in the testicles. For example, if a man is taking exogenous androgens (e.g., testosterone injections, anabolic steroids, prohormones), then blood testosterone levels can rise significantly. Since the pituitary gland is “seeing” these high blood testosterone levels, LH production drops which leads to potentially very low intratesticular testosterone concentrations which can be very detrimental to normal sperm production.
Testosterone Testing Specifics
Testing for testosterone is complex because of the way the hormone works within the body. For couples just trying to get an idea of their fertility potential, there is an easy way to evaluate testosterone levels; there is also a more complex (and accurate) form of testing for those working with a male fertility expert.
Total Testosterone
The simplest test just involves measuring the total amount of testosterone in the blood. The most commonly used definition of a normal total testosterone (T) level is 300 ng/dL or more. Below that, a man is considered to have a condition called hypogonadism (sometimes also called “low T”). Many male fertility experts use this as the normal cutoff in their practice. However, I generally like to see T levels in the 500–1,000 ng/dL range. This is felt to be threshold above which the hormonal environment is felt to be optimized- therefore 800 ng/dL is not necessarily any better than 500 ng/dL.
The rationale for what I consider to be a normal testosterone is that the traditional lower cutoff (300ng/dL) is based on studies that focused primarily on older males experiencing symptoms of low testosterone, not younger men with infertility problems. Other studies have been performed looking at average testosterone levels in normal men of different age groups. One such study found the following results:
Average total testosterone levels by age range (followed by 5% and 95% percentiles) [Simon D. Androgens and the Aging Male 1996]
1. Under 25 years 692 (408-956)
2. 25-29 years 669 (388-1005)
3. 30-34 years 621 (348-975)
4. 35-39 years 597 (329-945)
5. 40-49 years 546 (329-846)
6. 50-54 years 544 (289-936)
7. 55-59 years 552 (319-866)
By this study, a man who is under fifty and has a T of 330 ng/dL is only in the 5th percentile of men in his age group—that is, 95 percent of men had a higher T. I therefore like to get men to nearer the average T levels as shown by these studies. Another more recent study found that the average T levels for men aged 20-44 was 466. [Zhu A. JUrol 2022]
You should note that this is an area of significant controversy within the male infertility community. Some experts feel that boosting testosterone levels in men with fertility problems is likely not going to be of much benefit unless the testosterone levels are very low (for example, under 200 ng/dL). Unfortunately, there is not definitive data to date, but multiple studies confirm the finding that medications that increase T levels are associated with improvements in semen parameters. [Guo B. Andrology 2022]. My personal preference is that it makes sense to attempt to get total testosterone levels to ≥ 500ng/dL to try and re-create the typical hormonal environment present in most normal men, but other male fertility experts may have different opinions.
[Note: Some labs denote total testosterone levels using different units of measure: pg/µL instead of the standard ng/dL. The only difference is two decimal places. For example, 3.43 pg/µL = 343 ng/dL].
Free and Bioavailable Testosterone
Within the bloodstream, about 98 percent of testosterone is bound to proteins and about 2 percent is unbound. The unbound testosterone is free to enter the cells of the body and exert its masculinizing effects. Of the protein-bound testosterone, the two-thirds that are bound to albumin can break free and enter cells as well, while the one-third bound to sex hormone binding globulin (SHBG) is so tightly bound that it cannot break free and therefore is of no use to the cells. Labs can calculate either the free testosterone or the bioavailable testosterone (free testosterone plus albumin-bound testosterone) to get an idea of what amount of the total testosterone is actually usable by the cells.
This can be important because individual people have different amounts of SHBG, which “captures” the testosterone, making it inaccessible to the cells. Studies have shown that about 20 percent of men with a normal total testosterone actually have levels of free or bioavailable testosterone that are too low, because their bodies produce more SHBG, which ties up a larger portion of the testosterone.
Most of the current date shows that total testosterone is the most important factor in determining the presence of an adequate hormonal environment for sperm production. I therefore exclusively use total testosterone (not bioavailable or free) in the management of male infertility patients.
Estradiol and male infertility
Estradiol is a sex hormone with estrogenic (feminizing) actions, and many men are surprised to find out that they have estradiol in their bodies. In fact, estradiol in men plays an important role in maintaining normal bone health and strength. While in women the main source of estradiol is the ovaries, in men most of it is produced by an enzyme called aromatase, which is primarily found within the testicles, liver, and fat cells. Aromatase works by converting some of the testosterone and adrenal androgens into estradiol. Another 20 percent of estradiol is also produced directly by the testicles themselves. [deRonde W. ReprodBiolEndocrinol 2011]
There are several concerns with estradiol levels which are too high:
1) Impact on fertility- Estradiol levels which are too high can negatively impact sperm production and quality. [Raman JD. JUrol 2002]
2) Gynecomastia- Elevated estradiol levels can cause breast enlargement and tenderness
3) Potential cardiovascular risk- There is some evidence that elevated levels of estrogens can increase the risk of thrombosis and heart attacks. This data is from older men and no set cut-off levels have been determined and the risk is likely quite low in otherwise young healthy men. [Phillips GB. AtherosclThrombosVascBiol 1996] However, this data provides an extra reason to monitor the estradiol in men who are taking medications which can potentially increase their levels with a goal to keep them under about 60 pg/mL.
ELEVATED ESTRADIOL
Abnormally elevated estradiol levels can come in two forms:
1) Elevated estradiol levels- Normal estradiol levels are typically under 45 pg/mL. However, I usually do not start treatment for an elevated estradiol level without other symptoms unless it is over 59 pg/mL.
[Note: some labs report estradiol in different units of measure, ng/dL; 1 ng/dL = 1 pg/mL.].
2) Abnormal testosterone-to-estradiol ratio- The normal ratio between the total testosterone and estradiol (called the T/E ratio) should be 10:1 or greater. A T/E ratio of less than this can signify an imbalance between the testosterone and estradiol levels, which can potentially have a negative impact on sperm production. So, for example, if the total testosterone is 510 and the estradiol is 46, then the T/E ratio is 11.1 (510 divided by 46), which is normal. If, however, the total testosterone is 510 and
THE RISKS OF LOW ESTRADIOL LEVELS
There are 3 basic concerns of an estradiol that is too low: osteoporosis risk, symptoms of hypogonadism, and sexual function.
1) Osteoporosis and Symptoms of hypogonadism
Decreased estradiol levels have also been correlated with increases in body fat and decreased bone health. In contrast, lower testosterone levels tend to lead to symptoms such as decreased lean body mass, decreased muscle size and strength, and increased bone weakness. Further studies will need to be performed to further evaluate the relative contributions of estradiol and testosterone levels to the symptoms of hypogonadism.
2) Sexual function
A common misconception is that elevated estradiol levels in men can lead to symptoms such as decreased libido and erectile dysfunction. Actually, studies have found that keeping estradiol levels within the normal range may play an important role in maintaining normal male sexual function, while very low estradiol levels can contribute to low libido in some men. [Schulster M. AsianJAndrol 2016]. Studies of men taking exogenous testosterone were found to have better libido if the testosterone levels were >300 ng/dL AND estradiol levels were at least 5 ng/dL or higher. [Ramasamy R. EurUrol 2014]. Men in this study who had testosterone levels of <300 ng/dL still had better libido levels when their estradiol levels were 5 ng/dL or above.
[Note: some labs do not exactly quantify low levels of estradiol and just report the results as something like “<20ng/dL]
Follicle-Stimulating Hormone (FSH) and male infertility
FSH is a hormone made in the brain that tells the testicles to make sperm. A normal FSH is generally considered to be between 1.0 and 7.6 MIU/mL.
Low FSH Levels
If the FSH level is too low, then the brain may not be sending the correct signals to the testicles to make sperm. There are a number of reasons why the FSH may be low. One is the use of androgens (such as testosterone injections, anabolic steroids, and prohormones), which can suppress the secretion of FSH. Rare causes of excess androgens in the body can include androgen-secreting tumors or overactivity of the adrenal glands (such as congenital adrenal hyperplasia). Some men are born without the cells that produce FSH (an example of this is Kallman’s syndrome). Damage to the pituitary gland from previous surgery, trauma, or radiation can also decrease FSH production.
As mentioned above, a normal FSH is generally considered to be between 1.0 and 7.6 MIU/mL. A significantly low FSH would be considered 0.7 or less. I have seen men with normal sperm production with an FSH of 0.8 or 0.9, but levels in this range do raise the suspicion that something may be suppressing pituitary FSH production.
High FSH Levels
Men with low sperm counts often have an elevated FSH (over 7.6 MIU/mL). This indicates that the pituitary gland is responding normally to decreased sperm production by producing more FSH in an effort to “drive” the testicles to make more sperm. This elevated FSH is not a problem in itself, but rather a sign that the pituitary gland is responding normally to testicles that are not working properly. In this situation, I look for reversible reasons for the sperm production problem, such as varicoceles, low testosterone, etc.
Of note, certain medications (such as clomiphene citrate, tamoxifen, anastrazole) artificially elevate FSH levels through their mechanism of action- therefore it is always good to get a baseline FSH (along with testosterone, estradiol, and LH) before starting these medications.
FSH in Men with Azoospermia
When there is no sperm at all on semen analysis (a condition called azoospermia), the question is whether this is a sperm production problem or a problem with obstruction or ductal transport of sperm (in which case sperm production in the testicles should still be normal). FSH levels can provide an indication of whether sperm production is still adequate. If FSH levels are within the normal range (1.0–7.6 MIU/mL), then sperm production is usually still good and it is more likely that a blockage or sperm transport problem is present. However, if the FSH is high (over 7.6 MIU/mL), this suggests a sperm production problem.
Maturation Arrest and FSH
The use of FSH levels to determine whether azoospermia is the result of a sperm production problem or the result of a blockage or sperm transport problem works in most men. However, FSH levels in these situations are not always 100 percent accurate because of a sperm production problem called maturation arrest. With maturation arrest, the testicles are making sperm parts (which do not show up in a semen analysis) but not fully mature sperm. Since the cells within the testicles are busy making these sperm parts, the brain can be “tricked” into thinking that sperm production is actually fine, so it does not respond by increasing the secretion of FSH. In addition to normal FSH levels, testicle size in men with maturation arrest is often normal since the spermatogenic cells are present and busy, and these cells make up most of the volume of the testicle. Maturation arrest can be difficult to accurately diagnose and sometimes needs a testicular biopsy for a definitive diagnosis. This topic will be covered more fully in the azoospermia section of this website.
Thyroid-Stimulating Hormone (TSH) and male infertility
Thyroid problems are a relatively rare cause of male infertility. However, both severe hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid) can result in problems with sperm production and sperm quality in some men.
The normal range for the TSH is 0.4-3.0 µIU/mL. A TSH blood test should only be performed in men who have symptoms consistent with either hyperthyroidism or hypothyroidism:
1) Hypothyroidism: fatigue, cold intolerance, sleepiness, weight gain, muscle aches, abnormally slow heart rate, constipation, dry skin, brittle hair, decreased concentration or memory. With hypothyroidism, TSH levels are usually high (over 3.0 µIU/mL).
2) Hyperthyroidism: nervousness, fatigue, weakness, palpitations, heat intolerance, excessive sweating, diarrhea, insomnia, poor concentration, weight loss, abnormally fast heart rate, warm and moist skin. With hyperthyroidism, TSH levels are usually low (under 0.4 µIU/mL).
Prolactin and male infertility
Prolactin is a hormone made by the pituitary gland, which has multiple functions throughout the body (in women, it stimulates lactation). The normal prolactin level is generally considered to be 25 mcg/L or less. Of note, the recommendation for men with an elevated prolactin is to first get the blood test repeated, especially if the levels are borderline.
Mildly elevated prolactin levels (under 25-30 mcg/L) are not thought to cause infertility in men and should not be treated. However, significantly elevated levels of prolactin (30 mcg/L or more) can inhibit the release of FSH and LH from the pituitary gland, which can in turn decrease testosterone levels and cause problems with sperm production and quality. Symptoms can include ED, decreased libido, weight loss, and gynecomastia.
If prolactin levels are elevated, experts generally suggest MRI imaging of the pituitary gland with gadolinium to determine if a tumor may be present. Mildly elevated levels can be associated with benign microadenomas of the pituitary. Larger macroadenomas (>10mm) are also typically benign- they are often asymptomatic but can sometimes present with symptoms such as headaches, visual field changes, cranial nerve defects, and hypopituitarism. Although most tumors are benign and respond well to medical therapy, all men with pituitary tumors should have neurosurgical consultation.
Elevated prolactin levels are relatively uncommon in the male infertility population (0.35%) but this is a 35 fold increase in incidence over the general population (0.01%). [Ambulkar SS JUrol 2021]
Luteinizing Hormone (LH) and male infertility
LH is the hormonal signal from the brain that tells the testicles to make testosterone. LH testing is generally only needed when there is a question about how well the pituitary is functioning overall. Normal LH levels are in the range of 1.0–8.0 IU/L, but there’s a high degree of fluctuation in these tests, with results varying as much as 50 percent from test to test. Repeat testing may be indicated for unexpected results that do not seem to match the clinical picture.
If LH levels are low (under 1.0 IU/L), this usually is a result of either suppression of pituitary gland function or pituitary insufficiency. Suppression of pituitary gland function is most commonly the result of using androgenic substances such as testosterone injections, anabolic steroids, or prohormones, but rare causes can include androgen-secreting tumors or overactivity of the adrenal gland (such as congenital adrenal hyperplasia). Pituitary insufficiency can be the result of congenital problems, systemic illness, or past surgery, radiation, or trauma to the pituitary gland. Low LH levels combined with normal or high total testosterone levels is generally consistent with the use of androgenic substances, while low LH and low total testosterone levels are more likely consistent with pituitary insufficiency.
If the LH levels are normal (1.0–8.0 IU/L) but the total testosterone levels are low, this may mean the pituitary gland is not responding normally to the decreased testosterone levels.
Normally, elevated LH levels (over 8.0 IU/L) are the brain’s typical response if it senses that less testosterone than normal is being produced by the testicles. I interpret elevated LH levels based on total testosterone levels:
1) High LH (over 8.0 IU/L) and low total testosterone (under 300 ng/dL): normal response of the pituitary gland to decreased testosterone production. In this situation (low T) either the increased LH stimulation is not adequate to drive the testicles to produce normal levels of T, or the Leydig cells within the testicles are not functionally able to produce enough T despite adequate LH stimulation.
2) High LH (over 8.0 IU/L) and borderline or normal total testosterone (300–600 ng/dL): likely a normal physiologic response in which a testicle that was making less testosterone in the past is now responding to the increased stimulation of the extra LH in the bloodstream.
3) High LH (over 8.0 IU/L) and high total testosterone (over 600 ng/dL): may represent androgen insensitivity syndrome, in which the cells of the body do not respond properly to testosterone, and therefore the brain continues to make extra LH despite high levels of testosterone already being present in the bloodstream.
Note: As with FSH, certain medications (such as clomiphene citrate, tamoxifen, anastrazole) artificially elevate LH levels through their mechanism of action- therefore it is always good to get a baseline LH (along with testosterone, estradiol, and FSH) before starting these medications.
Inhibin B and male infertility
Inhibin B, a hormone produced within the testicles, is involved in the feedback regulation of spermatogenesis by the brain. When sperm production is good, inhibin levels are higher, which causes the brain to maintain normal levels of FSH secretion. However, when sperm production by the testicles decreases, inhibin levels fall, which stimulates the brain to secrete more FSH in an attempt to drive the testicles to make more sperm.
Normal ranges of inhibin levels have not yet been completely defined. One study found that men with normal sperm production (and average FSH of 3.8) had an inhibin B range of 173-238. In comparison, men with azoospermia due to Sertoli Cell Only (average FSH 25.9) had an inhibin B range of 18-27. [Grunewald S. 2013]. In my experience in men with azoospermia due to a blockage, inhibin B levels of ³100 pg/mL are usually consistent with the presence of decent sperm production.
Since inhibin levels are a more direct reflection of sperm production than the FSH levels that it helps to control, some researchers hope that someday it may be more clinically useful than FSH. However, at this point in time inhibin has not been studied nearly as extensively as FSH, the test is more expensive, and the test also has some of the same diagnostic limitations as the FSH test (such as falsely normal values in some azoospermic men with maturation arrest).
However, there is one situation in which I have found inhibin B levels to be very helpful. In men who have some type of blockage (such as a prior vasectomy) but who are also on an exogenous androgen (such as testosterone injections or anabolic steroids), there is often a question of how long they need to be off the androgens before their sperm production recovers to the point where they can have treatments such as a vasectomy reversal or sperm extraction. Since medications used to treat lower testosterone levels in men (such as clomiphene, tamoxifen, and anastrazole) can artificially elevate FSH levels, this makes monitoring FSH levels as a marker of the return of sperm production inaccurate. However, inhibin B levels do not seem to be impacted by medications such as clomiphene, tamoxifen and anastrazole, and therefore these levels can be monitored over time to help determine when sperm production has recovered. When inhibin levels reach at least 100 pg/mL, then it is good evidence that sperm production has rebounded to the point where vasectomy reversal or a sperm extraction procedure can be performed.