Luteinizing Hormone (LH)

Function

Luteinizing Hormone (LH) is a gonadotropin produced by the anterior pituitary gland. In females, a sharp rise in LH (the 'LH surge') triggers ovulation and the development of the corpus luteum. In males, LH stimulates the Leydig cells in the testes to produce testosterone. It is a key regulator of the hypothalamic-pituitary-gonadal axis.

Why it is Ordered

LH testing is fundamental in investigating infertility in both men and women. In women, it is used to track ovulation, evaluate menstrual irregularities, and diagnose menopause or Polycystic Ovary Syndrome (PCOS). In men, it helps determine if low testosterone is due to a primary testicular failure or a secondary pituitary/hypothalamic issue. It is also used in pediatrics to evaluate precocious or delayed puberty.

Associated Conditions

• PCOS: Often characterized by an elevated LH to FSH ratio.
• Primary Ovarian Failure/Menopause: LH levels rise significantly as the body attempts to stimulate non-responsive ovaries.
• Hypogonadotropic Hypogonadism: Low LH levels resulting in low sex hormone production due to pituitary or hypothalamic failure.
• Pituitary Adenomas: Tumors can either over-secrete LH or suppress its production.