Gonadotrophin-releasing hormone (GnRH)

On this page

What is GnRH?
Where is GnRH produced?
Function of GnRH
How GnRH is regulated
Causes of high GnRH
Causes of low GnRH
Testing GnRH
GnRH in traditional Chinese medicine
Acupuncture and GnRH
Chinese herbal medicine and GnRH
Diet and lifestyle
Related pages

1. What is GnRH?

Gonadotrophin-releasing hormone (GnRH) is a peptide hormone produced by specialised neurones in the hypothalamus, a small but powerful region at the base of the brain. GnRH sits at the very top of the reproductive endocrine cascade — without it, the pituitary gland cannot release follicle stimulating hormone (FSH) or luteinising hormone (LH), and without those two hormones the ovaries cannot grow follicles, ovulate, or produce oestrogens and progesterone. In men, GnRH is similarly required for sperm production and testosterone synthesis.

GnRH is released in pulses rather than as a continuous stream. The frequency and amplitude of these pulses change throughout the menstrual cycle and are tightly regulated by feedback signals from oestrogens, progesterone, leptin and a range of other hormones. This pulsatile pattern is essential — if GnRH is given continuously rather than in pulses, the pituitary gland actually shuts down LH and FSH production. This is the principle behind GnRH-agonist drugs used in IVF protocols.

Reference ranges vary from country to country and between laboratories. GnRH itself is not routinely measured in clinical practice because of its short half-life and pulsatile release; instead, fertility specialists measure FSH, LH and oestradiol to infer how the GnRH–pituitary axis is functioning. Always interpret hormone results alongside the reference range provided by the laboratory that ran your test.

2. Where is GnRH produced?

GnRH is produced by approximately 1,000–3,000 specialised neurones in the hypothalamus. These neurones project to the median eminence, where GnRH is secreted into the hypophyseal portal blood system — a small network of blood vessels that connects the hypothalamus directly to the anterior pituitary gland. This direct vascular connection allows GnRH to reach the pituitary in much higher concentrations than would be possible through the general circulation.

Because GnRH is secreted into this small portal system, almost none reaches the peripheral bloodstream — which is why measuring GnRH directly in venous blood is not clinically useful. Instead, the function of GnRH is assessed indirectly through its downstream effects on FSH and LH.

3. Function of GnRH

GnRH binds to GnRH receptors on cells of the anterior pituitary gland and stimulates them to produce and release FSH and LH. The pulse frequency of GnRH determines which of these two pituitary hormones is preferentially released:

Slow GnRH pulses (every 90–120 minutes) favour FSH release — appropriate for the early follicular phase when follicles need to grow.
Fast GnRH pulses (every 60 minutes or less) favour LH release — appropriate for triggering ovulation at mid-cycle.

This pulsatile control is one of the most elegant feedback systems in human physiology, and disturbances to it underlie many cases of unexplained infertility, hypothalamic amenorrhoea, anovulation and PCOS.

4. How GnRH is regulated

GnRH release is influenced by a wide range of hormonal and metabolic signals:

Oestrogens (oestradiol) — moderate levels of oestradiol normally suppress GnRH (negative feedback), but the high levels of oestradiol produced by a mature dominant follicle switch the system to positive feedback, triggering the LH surge and ovulation.
Progesterone — suppresses GnRH pulse frequency during the luteal phase and during pregnancy, preventing further follicle development.
Leptin — released from adipose (fat) tissue, leptin signals to the hypothalamus that the body has sufficient energy reserves to support reproduction. Low leptin (from low body fat, dieting or excessive exercise) suppresses GnRH and is one of the main causes of hypothalamic amenorrhoea.
Stress hormones (cortisol and CRH) — chronic stress suppresses GnRH and can stop ovulation entirely.
Kisspeptin — a key activator of GnRH neurones and a major mediator of how oestrogens, leptin and stress feedback onto the GnRH system.

5. Causes of high GnRH

GnRH levels rise in the following situations:

Mid-cycle LH surge — a normal physiological event that triggers ovulation.
Menopause and premature ovarian failure — without ovarian feedback, GnRH and consequently FSH and LH rise to high levels.
Castration or oophorectomy — removal of the gonads removes the negative feedback on GnRH.
Some forms of PCOS — an increased GnRH pulse frequency leads to disproportionately high LH compared with FSH, contributing to the hormonal pattern of PCOS.

6. Causes of low GnRH

GnRH may be low or insufficient in:

Hypothalamic amenorrhoea — caused by stress, low body fat, excessive exercise or chronic dieting.
Hyperprolactinaemia — high prolactin suppresses GnRH and causes anovulation.
Kallmann syndrome — a rare congenital condition in which GnRH neurones fail to develop properly.
Pituitary or hypothalamic tumours — rare, but should be considered in unexplained low FSH/LH.

7. Testing GnRH

GnRH is not measured directly in routine clinical practice because of its very short half-life (around two to four minutes) and its release into the small hypophyseal portal blood vessels rather than the systemic circulation. Instead, the integrity of the GnRH system is assessed by measuring FSH, LH, oestradiol, prolactin and progesterone at appropriate points in the menstrual cycle. Specialist endocrinology centres can perform a GnRH stimulation test, in which synthetic GnRH is administered and the LH and FSH response is measured — this is occasionally used to investigate delayed puberty, suspected pituitary disease or some types of hypothalamic dysfunction.

Reference ranges vary from country to country and between laboratories. Always interpret your test results against the laboratory's own reference range and discuss them with your doctor.

8. GnRH in traditional Chinese medicine

In traditional Chinese medicine, the role of GnRH most closely corresponds to the Kidney's role in governing reproduction and to the Liver's role in regulating the smooth flow of Qi. The Kidney provides the foundational essence (Jing) that drives reproductive maturation and ovulation, while the Liver ensures the smooth release and timing of hormonal signals. When the Liver Qi stagnates — as it commonly does under chronic stress — the rhythm of the GnRH pulse is disturbed, and ovulation may be delayed or absent.

Hypothalamic amenorrhoea, where GnRH is suppressed by stress or low body weight, is most commonly seen in TCM as a combination of Kidney deficiency and Liver Qi stagnation, often with an underlying Spleen Qi and Blood deficiency from undereating or excessive exercise.

9. Acupuncture and GnRH

Research has confirmed that acupuncture is able to influence GnRH release from the hypothalamus, which in turn regulates the pituitary gland and the release of FSH and LH. By acting on the hypothalamic-pituitary-ovarian (HPO) axis, acupuncture helps to restore a healthy GnRH pulse, which is the basis of regular ovulation and a regular menstrual cycle.

I use acupuncture in my clinic to support women with irregular cycles, anovulation, hypothalamic amenorrhoea, and PCOS — all of which involve disturbed GnRH signalling. Treatment is typically weekly for at least three menstrual cycles to allow the cycle to normalise.

10. Chinese herbal medicine and GnRH

Chinese herbal formulae such as Bu Shen Tiao Chong Tang, Zuo Gui Wan and Yu Lin Zhu support the Kidney essence and can help to restore the pulsatile rhythm of GnRH. Where Liver Qi stagnation is the dominant pattern, formulae such as Xiao Yao San (Free and Easy Wanderer) are used to restore the smooth flow of Qi and re-establish regular ovulation.

11. Diet and lifestyle

GnRH is highly sensitive to body weight, body fat percentage, stress and sleep. To support a healthy GnRH rhythm:

Maintain a body fat percentage of at least 22% — below this, leptin levels fall and GnRH is suppressed.
Eat regular meals and avoid prolonged fasting or restrictive dieting.
Sleep before 10 p.m. and aim for seven to eight hours per night.
Avoid excessive endurance exercise — three sessions of moderate cardio per week is sufficient.
Reduce psychological stress through mindfulness, meditation, yoga or counselling.