LHIU/L
Signal from the pituitary to the gonads
Also known as: Luteinising Hormone, Luteinizing Hormone
Typical optimal range
1.7–8.6 IU/L
A typical reference range is around 1.7–8.6 IU/L, though the exact figures vary between laboratories and differ by sex and, in women, by cycle phase, so always interpret your result alongside your own lab's reference interval. These figures are indicative — the range printed on your own lab report is the definitive one for your results.
Interpretation of LH follows NHS laboratory guidance and relevant NICE guidelines, including NG88 for PCOS, with clinical context always central to how a result is used.
What is LH?
Luteinising hormone (LH) is a signalling hormone made by the pituitary gland, a small gland at the base of the brain. In women, LH surges just before ovulation and helps regulate the menstrual cycle; in men, it travels via the bloodstream to the testes, where it stimulates Leydig cells to produce testosterone. Measuring LH in a blood sample is useful because it helps clinicians work out whether a hormonal problem originates in the pituitary or hypothalamus (a 'central' issue) versus in the ovaries or testes themselves.
What a high LH means
A raised LH result is a prompt to investigate further rather than a diagnosis in itself — it often suggests that the pituitary is working hard to stimulate gonads that are not responding as expected.
- Primary hypogonadism (men). In men, high LH paired with low testosterone is a classic pattern of primary hypogonadism, where the testes are not producing adequate testosterone despite strong pituitary signalling. Causes include Klinefelter syndrome, orchitis, or testicular injury, and a GP will usually request a repeat test alongside FSH and testosterone to confirm the picture.
- Polycystic ovary syndrome (PCOS). In women, a raised LH relative to FSH is commonly seen in PCOS, one of the most frequent hormonal conditions managed in UK primary and secondary care. NICE guideline NG88 covers the diagnosis and management of PCOS, and LH is typically interpreted alongside FSH, testosterone, and an ultrasound rather than in isolation.
- Menopause and perimenopause. As ovarian function declines, FSH and LH both rise because the pituitary tries to compensate for falling oestrogen levels. Elevated LH in a woman in her late forties or fifties is therefore a common and expected finding that fits the perimenopausal transition.
In women, LH rises sharply at mid-cycle as part of the normal ovulatory surge, so the timing of the blood draw relative to the menstrual cycle matters considerably; a single elevated result around day 14 may simply reflect this surge rather than a pathological finding.
What a low LH means
A low LH level, particularly when accompanied by low sex hormones, points to a problem originating in the pituitary or hypothalamus — sometimes called secondary or hypogonadotrophic hypogonadism — rather than in the gonads themselves.
- Exogenous steroid use. Use of anabolic steroids, testosterone replacement not under medical supervision, or high-dose corticosteroids can suppress the hypothalamic-pituitary axis, causing LH (and FSH) to fall. This suppression can persist for some time after stopping and warrants honest discussion with a GP.
- Hypothalamic suppression from metabolic or physiological stress. Significant calorie restriction, very low body weight, excessive exercise, or chronic stress can disrupt the hypothalamic pulse generator that drives LH secretion — a pattern sometimes called functional hypothalamic hypogonadism. Equally, obesity and insulin resistance can blunt LH signalling, so the relationship runs in both directions.
Low LH on its own, without accompanying symptoms or low sex hormones, may not be clinically significant, but the full hormonal picture — including FSH, testosterone or oestradiol, and prolactin — is needed before drawing conclusions.
Should I be worried?
A single LH result outside the reference range is rarely cause for alarm on its own — hormone levels fluctuate, and context is everything. If your result is flagged, the most useful next step is a conversation with your GP, who will want to know about your symptoms (changes in libido, energy, menstrual regularity, or fertility concerns), the timing of the test, and any medications or supplements you are taking. They will almost certainly want to look at LH alongside FSH, testosterone or oestradiol, and possibly prolactin before forming any view, and may suggest a repeat test to confirm the result. Fertility concerns or significant symptoms are a reason to seek that conversation promptly, but an unexpected result on a routine screen can usually be discussed at a routine appointment.
What actually helps
While medication or specialist treatment may be needed if there is a genuine hormonal disorder, several evidence-backed lifestyle habits support healthy hypothalamic-pituitary-gonadal axis function.
- Maintain a healthy body weight. Both excess body fat and being significantly underweight can disrupt LH secretion. Adipose tissue produces hormones and inflammatory signals that interfere with the hypothalamic pulse generator, so gradual, sustainable weight management is one of the most impactful steps, particularly in PCOS and obesity-related hypogonadism.
- Prioritise consistent, quality sleep. LH is released in pulses that are tightly coupled to sleep architecture, particularly slow-wave sleep. Chronic sleep deprivation and shift work are associated with disrupted gonadotrophin rhythms, so aiming for seven to nine hours of regular sleep supports normal pituitary signalling.
- Reduce exposure to endocrine-disrupting chemicals. Certain plasticisers (phthalates, BPA), pesticide residues, and some personal-care product ingredients can interfere with hormonal signalling. Practical steps include choosing glass or stainless-steel food containers, washing fresh produce, and checking labels on cosmetics — though absolute avoidance is neither possible nor necessary.
- Manage blood glucose and insulin resistance. Insulin resistance is closely linked to LH dysregulation in conditions such as PCOS. A diet that moderates refined carbohydrate load and supports insulin sensitivity — alongside regular physical activity — can help restore more normal LH pulsatility.
There is good supporting evidence that certain dietary patterns and foods help maintain the metabolic and hormonal environment in which LH can function normally.
Oily fish (salmon, mackerel, sardines)
Rich in omega-3 fatty acids, which have anti-inflammatory effects and are associated with improved insulin sensitivity — both relevant to healthy gonadotrophin regulation.
Whole grains (oats, brown rice, wholegrain bread)
Provide a slower glucose release than refined carbohydrates, supporting insulin sensitivity and reducing the hyperinsulinaemia that can disrupt LH secretion in PCOS.
Vegetables and legumes
High fibre intake supports a healthy gut microbiome and helps moderate oestrogen reabsorption, contributing to balanced hormonal milieu alongside healthy LH levels.
Nuts and seeds (especially walnuts, flaxseed)
Contain healthy fats, phytosterols, and lignans that support hormonal balance; walnuts in particular have been associated with improved reproductive hormone profiles in some small studies.
Zinc-rich foods (lean meat, shellfish, pumpkin seeds)
Zinc is required for pituitary hormone synthesis and testicular function; inadequate intake is associated with reduced LH and testosterone, particularly in men.
Dairy or fortified alternatives (for vitamin D and calcium)
Vitamin D deficiency is common in the UK and has been linked to disrupted reproductive hormone levels; ensuring adequate intake through diet and, where needed, supplementation as per NHS guidance supports overall endocrine health.
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Sources & further reading
These are reputable UK health resources for further reading. This page is written to be consistent with their guidance but is not a substitute for them.
For information only — not medical advice, and not individually reviewed by a clinician. Reference ranges vary by lab and individual. Discuss any results with a qualified clinician before making changes.