LH: the hormone behind testicular testosterone
Luteinizing hormone (LH) is released by the pituitary gland and stimulates the Leydig cells of the testicles to produce testosterone. On its own the number says little; paired with a testosterone level it tells your doctor where a hormone problem originates. LH is a blood test ordered by a urologist or primary-care doctor, usually in the same draw as FSH and testosterone.
What your number means
| Low | under 1.7 mIU/mL | The pituitary is not driving the testicles. With low testosterone this is secondary hypogonadism: a pituitary or hypothalamic cause, or, very often, suppression from testosterone therapy or anabolic steroids. |
|---|---|---|
| Normal | 1.7–8.6 mIU/mL | The signal from the brain is adequate. If testosterone is also normal, the axis is working. A normal LH with low testosterone is a grey zone that a specialist interprets with repeat testing. |
| High | above 8.6 mIU/mL | The pituitary is compensating for testicles that are not responding. With low testosterone this is primary hypogonadism, and sperm production is often affected as well. |
What it measures
LH is produced in the pituitary in response to pulses of GnRH from the hypothalamus. It binds to Leydig cells, which sit between the seminiferous tubules of the testicle, and drives them to make testosterone. The testosterone produced this way reaches concentrations inside the testicle far higher than in the blood.
Like FSH, LH is under negative feedback: testosterone and estradiol tell the hypothalamus and pituitary to reduce LH output. Low testosterone should therefore push LH up. When it does not, the problem is upstream of the testicles.
LH is measured on a morning blood sample. Because it is released in pulses every one to two hours, single values can fluctuate, and mildly abnormal results are repeated before acting on them.
Why it matters for sperm production
Sperm production depends on very high local testosterone inside the testicle, and that testosterone is made under LH stimulation. Without adequate LH, intratesticular testosterone falls, and sperm development stalls at an early stage even if the blood testosterone looks acceptable.
LH also explains one of the most common fertility mistakes. Testosterone taken from outside, whether as TRT or steroids, raises blood testosterone but suppresses LH. The Leydig cells stop producing testosterone locally, intratesticular levels collapse, and sperm production shuts down. A man can feel fine, with normal blood testosterone, and have no sperm.
The LH–testosterone pattern separates the two big categories of low testosterone. High LH with low testosterone means the testicles cannot keep up, and the semen analysis is often abnormal too. Low or inappropriately normal LH with low testosterone means the pituitary is not sending the signal, and both the hormone level and sperm production are often recoverable.
What raises or lowers it
LH rises when the testicles underperform: Klinefelter syndrome, testicular injury or surgery, chemotherapy or radiation, mumps orchitis, undescended testicles, and ageing. Aromatase inhibitors and clomiphene raise LH deliberately by blocking estrogen feedback at the pituitary.
LH falls with exogenous testosterone and anabolic steroids, with high prolactin, with pituitary tumours or damage, with opioid use, with severe illness, sleep deprivation, or heavy training combined with low calorie intake, and in congenital conditions such as Kallmann syndrome. Obesity lowers LH modestly through increased estradiol feedback.
Acute stress, a poor night's sleep, and the time of day all shift LH within its normal range. That is why a morning draw is standard and why one borderline value is rarely acted on.
What your doctor may do about it
When LH is low or normal alongside low testosterone, a urologist or reproductive endocrinologist may check prolactin, review medications and supplement use, and sometimes order pituitary imaging. If the cause is testosterone or steroid use, the first step is stopping under medical guidance. Medications such as clomiphene or hCG may be used to restore the signal to the testicles while preserving sperm production; TRT is avoided in men trying to conceive because it does the opposite.
When LH is high with low testosterone, the testicles themselves are the limitation. A specialist may test for chromosomal causes, examine testicular size, and assess sperm production directly. Testosterone replacement can relieve symptoms but will suppress whatever sperm production remains, so timing it around family plans, and banking sperm first, are part of the conversation.
LH is not treated in isolation. It is one line in a hormone panel that a doctor reads as a pattern with FSH, testosterone, estradiol, and prolactin.
When to retest
A borderline or unexpected LH should be repeated on a different morning, together with total testosterone, before any decisions are made. Two consistent readings carry far more weight than one.
After stopping testosterone or steroids, LH usually begins to recover within weeks, and doctors typically recheck the panel and a semen analysis every 3 months until sperm return. On clomiphene or hCG, a specialist will monitor LH and testosterone on their own schedule.
If your semen analysis is normal and you have no symptoms of low testosterone, LH testing is rarely needed. A semen analysis through Hera is the usual starting point; hormones are added when the results or symptoms call for them.
Common questions
What does high LH mean in a man?
High LH means the pituitary is working harder to stimulate testicles that are not responding well. When testosterone is low at the same time, this is primary hypogonadism, which often comes with reduced sperm production. When testosterone is normal, a mildly high LH may simply reflect testicles that need more drive to keep up, and is interpreted alongside FSH and the semen analysis.
What does low LH mean in a man?
Low LH means the signal from the brain is reduced. In men being evaluated for fertility, the most common cause is testosterone replacement or anabolic steroid use, which switches LH off. Other causes include high prolactin, pituitary problems, and opioid use. Low LH is usually the more treatable pattern, because the testicles are often healthy and simply waiting for a signal.
Can LH be normal and testosterone still low?
Yes, and it is a common finding. A normal LH in the face of low testosterone is "inappropriately normal": if the testicles were healthy and the pituitary was responding correctly, LH should be high. This pattern usually points to a mild upstream problem, such as obesity, sleep apnea, or medication effects, and is confirmed with repeat morning testing.
Does LH affect sperm count directly?
Indirectly but critically. LH does not act on sperm cells; it acts on Leydig cells to make testosterone, and that local testosterone is essential for sperm development. If LH is suppressed, intratesticular testosterone falls and sperm production drops, which is exactly why TRT and steroids cause low or zero sperm counts even when blood testosterone is normal.