The reference range for FSH in adult males is 2 – 12 IU/L and for LH is 2 – 9 IU/L.
FSH is measured in milli-international units per milliliter (mIU/mL). Normal results of this test for men are: 1.4 to 15.4 mIU/mL.
Elevated LH and FSH levels suggest primary hypogonadism, whereas low or low-normal LH and FSH levels suggest secondary hypogonadism. Normal LH or FSH levels with low testosterone suggest primary defects in the hypothalamus and/or the pituitary (secondary hypogonadism).
LH levels are normally low during childhood. Normal result for men over 18 years of age is around 1.8 to 8.6 IU/L. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples.
At the beginning of the cycle, LH and FSH levels usually range between about 5-20 mlU/ml. Most women have about equal amounts of LH and FSH during the early part of their cycle. However, there is a LH surge in which the amount of LH increases to about 25-40 mlU/ml 24 hours before ovulation occurs.
Normally this ratio is about 1:1 – meaning the FSH and LH levels in the blood are similar. FSH and LH are often both in the range of about 4-8 in young fertile women. In women with polycystic ovaries the LH to FSH ratio is often higher – for example 2:1, or even 3:1.
If you are a man, low LH levels may mean you have a disorder of the pituitary gland or the hypothalamus, a part of the brain that controls the pituitary gland and other important body functions.
It is also known as hypogonadotrophic hypogonadism due to low levels of LH and FSH resulting in decreased testosterone production. Secondary hypogonadism often occurs as part of a wider syndrome of hypopituitarism. Examples of causes can include: pituitary tumours and their treatment.
If you are male, abnormally high LH levels along with low levels of testosterone may mean that your testicles aren't responding to LH's signal to make more testosterone. Low levels of LH may mean that your pituitary gland isn't making enough LH. That can lead to too little testosterone production.
If you are a man, high FSH levels may mean: Your testicles have been damaged due to chemotherapy, radiation, infection, or alcohol abuse. You have Klinefelter syndrome, a genetic disorder affects sexual development in males. It often causes infertility.
Elevation of LH with normal T is predicted by multiple factors, reverts frequently and is not associated with unequivocal evidence of androgen deficiency. High LH is a biomarker for deteriorating health in aged men who tend to develop primary hypogonadism.
Sperm produced by FSH
FSH has a very significant role for both women and men. FSH is responsible for testicular growth and the production and maturation of sperm cells. Similar to LH, a low FSH level means low libido or inability to conceive while a high FSH means damaged testicles.
Research also suggests that FSH levels less than 10 IU/mL demonstrate likely normal ovarian reserve, 10 to 20 IU/mL is intermediate, and an FSH greater than 20 IU/mL is a poor prognosis for spontaneous ovulation due to low ovarian reserve [3].
How do low LH and FSH affect male fertility? Both LH and FSH are vital to the proper production of sperm. Low levels of these hormones can be at least partly responsible for low sperm counts, which is the biggest cause of infertility in men. Normally, diagnosis would begin with a semen analysis.
In both sexes, LH contributes to the maturation of primordial germ cells. In men, LH causes the Leydig cells of the testes to produce testosterone. In women, LH triggers the creation of steroid hormones from the ovaries [1].
Male hypogonadism usually is treated with testosterone replacement to return testosterone levels to normal. Testosterone can help counter the signs and symptoms of male hypogonadism, such as decreased sexual desire, decreased energy, decreased facial and body hair, and loss of muscle mass and bone density.
However, erectile dysfunction and infertility may occur secondary to low LH levels caused by compression of the normal gonadotroph cells. In women presenting with low FSH levels or high FSH levels secondary to ovarian failure, manifestations include oligomenorrhea or amenorrhea.
Primary hypogonadism is associated with low levels of testosterone and high-normal to high levels of LH and FSH. Secondary hypogonadism is associated with low levels of testosterone and normal to low levels of LH and FSH.
If you have low levels of FSH resulting in a low sperm count or poor sperm quality, there is a good chance that fertility treatment can help. The treatments most frequently recommended are Intrauterine Insemination (IUI) or In Vitro Fertilisation (IVF).
LH and FSH are the main regulating hormones of the hypothalamic-pituitary-gonadal axis, and their deficiency can present as delayed puberty, reproductive abnormalities, and hypogonadism depending on whether the condition occurs before or after puberty.
Lower-than-normal FSH levels usually lead to incomplete development during puberty in children. They lead to poor ovarian or testicular function in adults, which can lead to infertility. This condition is called hypogonadotropic-hypogonadism, and it's usually caused by issues with your pituitary gland or hypothalamus.
A high or low LH level isn't simply good or bad. For instance, a surge in your LH can show that you're about to ovulate. You're most likely to become pregnant at this time. This information that LH provides about your fertility is helpful if you're trying to have a baby.