Luteinizing Hormone (LH)

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Luteinizing Hormone (LH) is secreted by the anterior pituitary gland and is essential for normal reproductive function in both sexes. In women, LH surge triggers ovulation and supports corpus luteum formation. In men, LH stimulates Leydig cells in the testes to produce testosterone.

Normal Reference Ranges

• Ages 1 day–<10 years: 0.20–1.40 mIU/mL

• Females (9–99 years)

  • Follicular phase: 2.20–12.60 mIU/mL

  • Mid-cycle peak: 14.00–95.60 mIU/mL

  • Luteal phase: 1.00–11.40 mIU/mL

• Males (9–99 years): 1.30–8.60 mIU/mL

Key Functions

• Women:

  • Triggers maturation and release of the ovarian egg (ovulation)

  • Supports corpus luteum to produce progesterone

• Men:

  • Stimulates testosterone synthesis by Leydig cells in the testes

  • Maintains sperm production

Conditions Indicated by Abnormal LH

• Elevated LH in Women:

  • Polycystic Ovary Syndrome (PCOS)

  • Premature ovarian failure or menopause

• Low LH in Women:

  • Hypothalamic or pituitary disorders

  • Functional hypothalamic amenorrhea

• Elevated LH in Men:

  • Primary testicular failure

• Low LH in Men:

  • Secondary hypogonadism (pituitary/hypothalamic dysfunction)

  • Infertility

Clinical Symptoms

• LH Deficiency:

  • Women: Irregular or absent periods, anovulation, infertility

  • Men: Low libido, erectile dysfunction, decreased muscle mass

• LH Excess:

  • Women: Signs of hyperandrogenism, ovarian hyperstimulation

  • Children: Precocious (early) puberty

Diagnosis

• Blood Test: Measure serum LH, typically alongside:

  • Follicle-Stimulating Hormone (FSH)

  • Estradiol (E₂) in women

  • Testosterone in men

• Timing in Women: Correlate draw with menstrual phase for accurate interpretation

Frequently Asked Questions

1. What role does LH play in fertility?
   LH surge is required for ovulation and luteal phase support in women; in men, LH ensures adequate testosterone for sperm production.

2. How do LH levels affect menstrual cycles?
   Low LH can prevent ovulation; a mid-cycle LH spike is necessary for egg release.

3. What causes abnormal LH levels?
   Pituitary or hypothalamic disorders, ovarian or testicular failure, PCOS, menopause, and certain tumors.

4. How is an LH test performed?
   A simple blood draw; timing in women should match the cycle phase of interest.

5. What treatments address abnormal LH levels?
   Depending on cause: hormone replacement, ovulation induction agents, pituitary/hypothalamic therapies, or addressing underlying endocrine disorders.

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