What is Follicle-Stimulating Hormone (FSH)?

Follicle stimulating hormone (FSH) is a pituitary hormone that regulates growth, sexual development and reproduction, including menstruation, follicular development and ovulation.

FSH is regulated, at least in part, by GnRH produced in the hypothalamus in response to multiple signals including circulating levels of sex hormones. FSH interacts with receptors on ovarian follicles and is the major survival factor for the maturing follicles. A surge in FSH levels occurs in the middle of the menstrual cycle leading to ovulation.

In women, FSH helps manage the menstrual cycle and stimulates the ovaries to produce eggs. The test is used to help diagnose or evaluate:

– Menopause
– Women who have polycystic ovary syndrome, ovarian cysts
– Abnormal vaginal or menstrual bleeding
– Problems becoming pregnant, or infertility

For men:

In men, FSH promotes spermatogenesis and androgen responsiveness in the testes. Thus, FSH is essential for sexual maturation and reproduction in both men and women.

The test is used to help diagnose or evaluate:

– Problems becoming pregnant, or infertility
– Men who do not have testicles or whose testicles are underdeveloped

Reference ranges:

Follicular Phase: 3.03 – 8.08 IU/L

Mid-Cycle Peak: 2.55 – 16.69 IU/L

Luteal Phase: 1.38 – 5.47 IU/L

Postmenopausal: 26.72 – 133.4 IU/L

Males: 0.95 – 11.95 IU/L

Higher levels:

High FSH levels in women may be present:

– During or after menopause, including premature menopause

– When receiving hormone therapy

– Due to certain types of tumor in the pituitary gland

– Due to Turner syndrome

High FSH levels in men may mean the testicles are not functioning correctly due to:

– Advancing age (male menopause)

– Damage to testicles caused by alcohol abuse, chemotherapy, or radiation

– Problems with genes, such as Klinefelter syndrome

– Treatment with hormones

– Certain tumors in the pituitary gland

Lower levels:

Low FSH levels in women may be present due to:

– Being very underweight or having had recent rapid weight loss

– Not producing eggs (not ovulating)

– Parts of the brain (the pituitary gland or hypothalamus) not producing normal amounts of some or all of its hormones

– Pregnancy

Low FSH levels in men may mean parts of the brain (the pituitary gland or hypothalamus) do not produce normal amounts of some or all of its hormones.