What does LH do?
LH, luteinizing hormone, is the messenger that tells your testes to make testosterone. The pituitary gland at the base of the brain releases it, on instructions from the hypothalamus above. MedlinePlus describes LH as the hormone that causes the testicles to make testosterone, which in turn supports sperm production.
The system runs on feedback. When testosterone is low, a healthy pituitary releases more LH; when testosterone is high, LH falls. That loop is what makes LH useful, because it shows whether the problem behind low testosterone sits in the testes or higher up.
What is the normal LH range for adult men?
The MedlinePlus encyclopedia lists a normal LH of 1.8 to 8.6 IU/L for men over 18. Your lab may print a slightly different range depending on its method, so compare your result with the range on your report.
A number inside that range is not automatically reassuring. An LH of 4 IU/L is normal next to a testosterone of 550 ng/dL, but it is too low next to a testosterone of 200 ng/dL, because a healthy pituitary should be pushing harder.
Why must LH be read with same-morning testosterone?
Because an LH value has no meaning on its own. It shows whether the pituitary is responding appropriately to the testosterone level at that moment. The Endocrine Society guideline classifies low testosterone by pairing it with LH and FSH: primary hypogonadism comes with raised gonadotropins, while secondary hypogonadism comes with low or “inappropriately normal” ones. You can only call LH inappropriately normal if you know the testosterone from the same draw.
Timing matters for a second reason. LH is released in pulses, and a study of repeated hormone measurements in men found that short-term variability was greater for pulsatile hormones such as LH. A testosterone from Monday and an LH from Thursday may describe two different moments. Drawn together in the early morning, they describe one.
| Testosterone, same morning | LH | What it suggests |
|---|---|---|
| Low | High | Primary: the testes are not responding to the signal |
| Low | Low or normal | Secondary: the signal from the pituitary or hypothalamus is weak |
| Normal | High | The testes may be working harder to keep testosterone normal |
| Normal or high, on TRT | Very low | Expected suppression from treatment |
The AUA guideline asks for LH in men with low testosterone and notes that the literature does not define a single LH level below which further testing is needed, which is another reason LH is always read in context.
What raises or lowers LH?
High LH in men usually points to the testes. MedlinePlus lists testicular injury, mumps, testes that did not develop normally, germ cell tumors and chromosomal conditions such as Klinefelter syndrome among the causes. Our page on primary hypogonadism covers this group.
Low LH points higher up. Causes include pituitary or hypothalamic disease, high prolactin, obesity, long-term opioid use, and current or past use of testosterone or anabolic steroids. Our page on low testosterone with low LH walks through that workup, including the prolactin test.
What happens to LH on TRT and after stopping?
On testosterone therapy, a very low LH is expected: the pituitary senses plenty of testosterone and goes quiet. That is the same reason TRT lowers sperm production. When you stop, LH climbing back into range is one of the first signs your own system is restarting, as our page on blood work after coming off TRT explains. On HCG, LH is not a useful marker, because HCG itself does the job LH would do.
How to prepare for an LH test
- Book an early-morning draw, together with total testosterone and an FSH test.
- Come fasting, since testosterone is drawn from the same sample.
- Ask your clinician about stopping biotin for at least 72 hours, because the Endocrine Society notes it can interfere with LH and FSH assays.
- Tell your provider about any testosterone, steroids, HCG, fertility medicines or opioids you use, and do not stop a medicine unless told to.
How Ultimate Male uses LH
LH is not one of the four markers in the TRT pre-screening panel, which covers total testosterone, estradiol, PSA and a complete blood count. Your provider adds LH and FSH when testosterone comes back low or borderline, so the cause can be read from the same morning draw, and before any decision about HCG.
The result shapes the plan. A testicular cause, a pituitary cause and a reversible one such as weight or medicines each lead somewhere different, and only some lead to testosterone therapy. If you already have an LH result from elsewhere, bring it with the testosterone from the same draw, and ask on the free 10-minute call whether anything needs repeating.
