Luteinizing Hormone (LH) is a vital hormone involved in the regulation of the reproductive system. It is secreted by the anterior pituitary gland and plays a key role in controlling sexual development and reproductive function in both males and females. In women, LH is responsible for triggering ovulation and supporting the menstrual cycle, while in men, it stimulates the production of testosterone.
What Does the Luteinizing Hormone (LH) Do?
Luteinizing Hormone (LH) plays a central role in regulating the function of the gonads—ovaries in females and testes in males. It is essential for fertility, hormone production, and proper sexual development. Its functions differ between the sexes but are equally important.
In Females
LH works in coordination with Follicle-Stimulating Hormone (FSH) and plays a crucial role in the menstrual cycle, ovulation, and hormone regulation.
1. Ovulation Trigger
- LH surge (a sudden rise in LH levels) occurs in the middle of the menstrual cycle.
- This surge triggers the release of a mature egg from the dominant ovarian follicle.
- It is the key hormonal event that causes ovulation, usually around day 14 in a 28-day cycle.
2. Corpus Luteum Formation
- After ovulation, LH helps the ruptured follicle transform into the corpus luteum.
- The corpus luteum secretes progesterone, which prepares the uterine lining (endometrium) for possible pregnancy.
3. Support of Early Pregnancy
- If fertilization occurs, LH indirectly supports early pregnancy by maintaining the corpus luteum until the placenta takes over progesterone production.
In Males
In males, LH is essential for testosterone production and overall sperm development.
1. Stimulates Leydig Cells
- LH acts on Leydig cells in the testes, which are responsible for producing testosterone.
2. Supports Spermatogenesis
- Testosterone produced under LH stimulation is critical for the maturation of sperm cells (spermatogenesis) within the seminiferous tubules.
3. Maintains Male Secondary Sexual Characteristics
- Through testosterone, LH indirectly supports:
- Facial and body hair growth
- Deepening of the voice
- Muscle mass development
- Libido and sexual function
Normal Levels of Luteinizing Hormone (LH)
Luteinizing Hormone (LH) levels vary depending on a person’s age, sex, and stage of reproductive life (e.g., menstrual cycle phase in women, puberty, menopause).
Females
| Phase | Normal LH Level (IU/L) |
|---|---|
| Follicular Phase | 1.9 – 12.5 |
| Ovulation (LH surge) | 8.7 – 76.3 |
| Luteal Phase | 0.5 – 16.9 |
| Postmenopausal | 15.9 – 54.0 |
- Follicular Phase: Early part of the menstrual cycle before ovulation.
- Ovulation: Sharp rise (LH surge) that triggers the release of an egg.
- Luteal Phase: After ovulation, when the corpus luteum forms.
- Postmenopause: LH increases due to lack of negative feedback from estrogen.
Males
| Adult Males | 1.5 – 9.3 IU/L |
- LH stimulates testosterone production by acting on Leydig cells.
Children (Pre-puberty)
| Both Sexes (Prepubertal)| < 0.1 – 6.0 IU/L |
- Levels begin to rise with the onset of puberty.