The importance of luteinizing hormone (LH)

What is luteinizing hormone?
Luteinizing hormone (LH) is a crucial hormone in both males and females. In females, it regulates the function of the ovaries, while in males, LH regulates the function of the testes (1).

Why is luteinizing hormone so important in females?
In the first half of each menstrual cycle, LH stimulates the ovarian follicles of the ovary to produce estradiol. At mid-cycle (around day 14), there is a sharp increase in LH levels (known as the “LH surge”), which causes ovulation–the rupture of the ovarian follicle and release of an egg from the ovary. LH then stimulates the corpus luteum (formed from the ruptured ovarian follicle) to produce progesterone. Progesterone is needed to support a pregnancy if fertilization of the egg has occurred (1).

Why is luteinizing hormone so important in males?
LH is essential for testosterone production by the stimulation of the Leydig cells in the testes. This testosterone is needed for sperm production, as well as other effects all around the body, including increased muscle mass, growth of facial and body hair, and generation of a deeper voice (1).

What issues are related to elevated luteinizing hormone levels?
Both too much or too little LH can affect fertility. High levels of LH are associated with polycystic ovary syndrome (PCOS) in women, which is estimated to affect 6–12% of U.S. women of reproductive age (2). PCOS is characterized by an imbalance in LH and follicle-stimulating hormone (FSH) levels, which leads to higher-than-normal levels of testosterone causing irregular periods and ovulation issues (1). Elevated LH levels have also been linked to an increased risk of miscarriage (3).

High LH levels can also be caused by decreased sex steroid production (estrogen from the ovaries), which can occur in premature ovarian failure, where the ovaries stop working earlier than the normal menopause age of 40–58 years (1).

There are also genetic conditions that cause high LH levels, including Klinefelter’s syndrome in males and Turner syndrome in females. Generally, people affected by these conditions are infertile (1).

What issues are related to low luteinizing hormone levels?
Healthy LH levels are required for normal testicular and ovarian function, so if there is not enough LH, infertility can occur.

Kallmann’s syndrome is an example of a male condition associated with low LH levels. This occurs due to lower levels of gonadotrophin-releasing hormone and therefore reduced stimulation of the pituitary gland to synthesize and release LH (1).

Low LH levels in females can result in irregular periods and an absence of ovulation, therefore meaning that egg fertilization is impossible (1). Various conditions can contribute to low LH levels, including eating disorders, hyperprolactinemia, and hypopituitarism (4).

How can I check my LH levels?
We offer a Luteinizing Hormone test to measure your LH levels from a small blood sample self-collected from a finger prick. LH is also included in several of our larger Women’s Health panels: Women’s Fertility Panel, Women’s Hormone Panel, Women’s Health Hormone Panel, and Women’s Perimenopause Panel.

Please note that due to fluctuating LH levels in women of reproductive age, the blood sample should be collected on the third day of your menstrual cycle for optimal results.

1. Luteinising hormone. You and your hormones, an education resource from the Society for Endocrinology. Reviewed Feb 2018.
2. PCOS (Polycystic Ovary Syndrome). CDC. Reviewed March 2020.
3. Homburg R, et al. (1988). Influence of serum luteinising hormone concentrations on ovulation, conception, and early pregnancy loss in polycystic ovary syndrome. BMJ. 297 (6655), 1024-1026.
Ross GT. (1985). Disorders of the ovary and female reproductive tract. In: Wilson JD, Foster DW, editors. Williams Textbook of Endocrinology, 7th ed. Philadelphia: WB Saunders Co. 206-258.