LH

LH (luteinising hormone) is a pituitary hormone that triggers ovulation and stimulates progesterone production in women, and testosterone production in the testes in men. Testing investigates irregular cycles and infertility, suspected polycystic ovary syndrome and low testosterone, almost always together with FSH.

Who the test is for

• women with irregular or absent periods;
• women and men undergoing infertility investigation (more in the article on causes of male infertility);
• women with suspected polycystic ovary syndrome (PCOS);
• women with suspected early menopause or premature ovarian insufficiency, alongside FSH;
• men with low testosterone, to determine whether the cause is in the testes or pituitary;
• children with early or delayed puberty and people with suspected pituitary dysfunction, as directed by a doctor.

What LH is and what it shows

LH is secreted by the anterior pituitary under hypothalamic control, in pulses, so its level changes during the day. In women it is low to moderate in the first half of the cycle and rises sharply at mid-cycle. This rise triggers ovulation, usually within 24 to 36 hours. After ovulation LH stimulates the corpus luteum to produce progesterone. In a cycle without ovulation, this rise is usually absent. In men LH stimulates cells in the testes to produce testosterone.

LH and FSH have different roles and do not replace each other, but are interpreted together. Both depend on feedback: when the ovaries or testes function less effectively, the pituitary secretes more LH and FSH, while both are low when the problem is in the pituitary or hypothalamus.

Save with a panel

Test LH is also included in these panels.

Postmenopause assessment panelFSH, oestradiol, LHPrice of individual tests: 54.00€49.00€Details ›Perimenopause assessment panelFSH, LH, oestradiol, progesterone, TSHPrice of individual tests: 82.00€74.00€Details ›Early menopause assessment panelFSH, LH, oestradiol, progesterone, prolactin, TSHPrice of individual tests: 100.00€90.00€Details ›

All panels including LH (15) ›

Preparation and sample

Blood is taken from a vein. Fasting is unnecessary for LH alone. Women with regular cycles usually give blood early in the cycle, between the 2. and 5. days, most often the 2. or 3. day (the first day of menstruation is day 1.), alongside FSH and oestradiol, or as instructed by a doctor. With absent periods and after menopause, blood can be taken on any day. Men give blood in the morning because LH is most often measured alongside testosterone, which is collected fasting between 7 and 10.

Hormonal contraception, hormone therapy and testosterone preparations change LH levels, so tell your doctor if you take them. If you take biotin (for example hair and nail supplements), mention this during collection.

LH and ovulation

Home urine ovulation tests detect the LH surge and help identify fertile days. A single blood collection can easily miss this short rise, so blood LH is not used to determine ovulation day. A doctor checks whether ovulation has occurred using progesterone in the second half of the cycle, around 7 days before the expected period (for a 28-day cycle, between the 21. and 23. days).

How to interpret the result

LH is expressed in IU/L. The reference range depends on sex, age, cycle phase and method and is printed on the report. A doctor interprets it alongside FSH, oestradiol or testosterone, the cycle pattern and symptoms.

• Raised LH alongside raised FSH in women occurs in menopause and premature ovarian insufficiency. In men, high LH with low testosterone suggests testicular damage. High LH at mid-cycle is expected.
• In polycystic ovary syndrome LH is often relatively raised compared with FSH. However, the LH/FSH ratio is not part of the diagnostic criteria: a normal ratio does not rule out PCOS, and diagnosis is based on cycles, signs of excess male hormones and ultrasound.
• Low LH may indicate reduced pituitary or hypothalamic function. It can be lowered by major weight loss, exhausting training, stress, raised prolactin, pregnancy, hormonal contraception and, in men, testosterone or anabolic steroid use.

Because secretion occurs in pulses, a single borderline result is insufficient for a conclusion, so a doctor repeats measurement if necessary.

How to arrange testing

You can have blood taken without an appointment or referral at one of our branches across Croatia (listed under Contact). Prices for all tests and panels are available in the service price list. In fertility investigation, LH is most often measured as part of the Fertility investigation panel, and when PCOS is suspected as part of the PCOS panel.

Frequently asked questions

On which cycle day is LH measured?

With a regular cycle, between the 2. and 5. days, most often the 2. or 3. day, together with FSH and oestradiol, or as directed by a doctor. If periods are absent, blood can be collected on any day and a doctor interprets the result alongside other hormones.

What does high LH mean?

High LH at mid-cycle is normal and signals impending ovulation. Outside that period, high LH with high FSH suggests reduced ovarian or testicular function, while with normal FSH it can accompany polycystic ovary syndrome. A doctor draws conclusions alongside other findings.

Is the LH to FSH ratio important for PCOS?

A raised LH/FSH ratio is often seen in PCOS but is not part of the diagnostic criteria. A doctor makes the diagnosis based on cycles, signs of excess male hormones, ultrasound and, in adult women, if needed, AMH.

Why is LH measured in men?

With low testosterone, LH indicates where the cause lies. High LH means the pituitary is stimulating the testes but they are not responding, while low or normal LH with low testosterone suggests a pituitary or hypothalamic disorder.