How to prepare for the ‘LH’ test: rules for taking it
Luteinizing hormone (LH) is the ‘commander’ of the sex glands: it triggers the synthesis of testosterone in the testes and ovulation in the ovaries. An LH test helps to understand where exactly a hormonal disorder arose — in the sex glands or in the pituitary. But the hormone is released in pulses, and its level depends on the cycle phase and on the intake of any sex hormones. The editorial team explains how to take this test correctly.
The role of LH and indications for the test
LH is synthesised by the gonadotropic cells of the anterior pituitary under the influence of gonadotropin-releasing hormone (GnRH) from the hypothalamus. In men, LH stimulates the Leydig cells to produce testosterone. In women, the mid-cycle LH peak triggers ovulation, and in the luteal phase the hormone supports the corpus luteum, which produces progesterone.
The system works on the principle of negative feedback: when there are many sex hormones, the hypothalamus and pituitary reduce the release of GnRH and LH; when there are few — they increase it. That is precisely why LH is a key indicator for distinguishing ‘primary’ from ‘secondary’ disorders.
In men, the test is ordered together with testosterone when hypogonadism is suspected, in infertility, gynecomastia, delayed puberty. The Endocrine Society guideline (Bhasin et al., 2018) recommends measuring LH and FSH in all men with confirmed low testosterone in order to determine the level of the lesion.
In women, LH is measured in cycle disorders, infertility, suspected polycystic ovary syndrome, as well as to determine the timing of ovulation. Home ovulation tests actually measure precisely the rise of LH in the urine.
Pulsatile secretion: why a single test can be misleading
GnRH is released by the hypothalamus not evenly but in pulses, and LH follows this rhythm. Classic works on GnRH physiology, summarised by Crowley and colleagues (1985), showed that in adult men pulses occur approximately every 1–2 hours, while in women the frequency and amplitude change depending on the cycle phase.
The practical significance of this fact: a single LH value is a ‘snapshot’ at a random moment of the pulsatile rhythm. If blood was taken at the peak, the result will be higher; if between pulses — lower. For most clinical tasks such accuracy is sufficient, but borderline values are worth rechecking.
In research and complex clinical situations, several samples are sometimes taken at 15–20-minute intervals and pooled or measured separately. In routine practice this is rarely needed, but it explains why a doctor may ask to repeat the test.
For the patient the main takeaway is simple: keep the draw conditions the same, and do not draw conclusions from a single ‘slightly elevated’ or ‘slightly reduced’ LH.
When to take it: for women and men
In women with a regular cycle, baseline LH is usually measured on day 2–5 of the cycle together with FSH and estradiol. In this period the ratio of gonadotropins is most informative for assessing ovarian function. To detect the ovulatory peak, LH is measured in the middle of the cycle — often in the urine using tests.
In men, LH is taken in the morning, together with morning testosterone, in order to interpret both indicators at one point. Although for LH itself the circadian rhythm is not as important as for testosterone, a joint draw is convenient and logical.
| Group | When to take it | Together with what |
|---|---|---|
| Women with a regular cycle | Day 2–5 of the cycle (baseline assessment) | FSH, estradiol, and if needed AMH, prolactin |
| Women, determining ovulation | Mid-cycle, daily (often a urine test) | Ultrasound monitoring |
| Women with amenorrhea or an irregular cycle | On any day, as prescribed by the doctor | FSH, estradiol, prolactin, TSH, hCG |
| Men | In the morning, fasting | Total testosterone, FSH, SHBG, prolactin |
- have it done in the morning, fasting, if the same draw includes testosterone;
- the day before — usual sleep, without intense training or alcohol;
- do not take it during an acute illness;
- indicate on the referral the day of the cycle and all hormonal drugs;
- report biotin intake.
Drugs and conditions that alter LH
Any exogenous sex hormones suppress LH through feedback. This applies to testosterone and other androgens, anabolic steroids, estrogens and progestins, including hormonal contraceptives. The review by Rahnema and colleagues (2014) describes that in men, after taking anabolic steroids, suppression of LH and FSH can persist for months.
GnRH analogues and antagonists, used in the treatment of prostate cancer, endometriosis and in reproductive medicine, also radically alter LH. Gonadotropins and hCG can interact with some test systems, so they must be reported.
Among conditions that lower LH are hyperprolactinemia, pronounced energy deficit and excessive training, severe chronic diseases, tumours of the hypothalamic-pituitary region. LH is raised by primary testicular or ovarian failure, menopause, Klinefelter syndrome, and in women often — polycystic ovary syndrome.
Biotin in high doses may affect gonadotropin immunoassays, about which the FDA has warned. If you take such supplements, ask the laboratory how long before the test you need to avoid them.
You should not discontinue prescribed hormone therapy on your own in order to ‘check your own hormones’. The decision on when and how to assess the body's own secretion is made by the doctor.
How LH is interpreted together with other hormones
A single LH without testosterone (in men) or without estradiol and the day of the cycle (in women) has almost no diagnostic value. The point of the test lies in the ratio of the indicators.
Low testosterone with high LH indicates a primary testicular lesion: the pituitary is ‘shouting’, but the gland does not respond. Low testosterone with low or ‘normal’ LH indicates secondary (central) hypogonadism — a problem in the hypothalamus or pituitary. This is exactly the approach used in the EMAS study (Wu et al., 2010) to classify hypogonadism in older men.
Low LH and low testosterone in a person who took androgens is a typical picture of axis suppression, rather than an independent pituitary disease, although the doctor must rule out other causes.
In women, an elevated LH/FSH ratio was once considered a sign of polycystic ovary syndrome, but modern diagnostic criteria do not rely on this indicator. Therefore the interpretation should be left to a gynecologist-endocrinologist.
Editorial conclusions
LH is a key indicator for understanding at what level a hormonal disorder has arisen. It is released in pulses, so a single result should be assessed with caution.
For women, baseline LH is taken on day 2–5 of the cycle; for men — in the morning together with testosterone. Be sure to inform the doctor about hormonal drugs, contraceptives, androgens and biotin.
Interpretation of LH is always complex and should take place together with a doctor.
We also advise reading our articles on preparing for the FSH, prolactin and total testosterone tests.
References
- Bhasin S, Brito JP, Cunningham GR, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744.
- Crowley WF Jr, Filicori M, Spratt DI, Santoro NF. The physiology of gonadotropin-releasing hormone (GnRH) secretion in men and women. Recent Prog Horm Res. 1985;41:473–531.
- Wu FC, Tajar A, Beynon JM, et al. Identification of late-onset hypogonadism in middle-aged and elderly men. N Engl J Med. 2010;363(2):123–135.
- Rahnema CD, Lipshultz LI, Crosnoe LE, et al. Anabolic steroid-induced hypogonadism: diagnosis and treatment. Fertil Steril. 2014;101(5):1271–1279.
- Strauss JF, Barbieri RL (eds). Yen & Jaffe's Reproductive Endocrinology. 8th ed. Elsevier; 2019.
- U.S. Food and Drug Administration. The FDA warns that biotin may interfere with lab tests: FDA safety communication. 2017.
Andriy Melnyk
A strength-sports coach and author of programs for beginner and intermediate levels. Writes about training planning.
