FSH Levels

Definition - What does FSH Levels mean?

FSH (follicle-stimulating hormone) levels in women are measured on day 3 of the menstrual cycle to evaluate menstrual irregularities, fertility problems, and determine a woman's potential to conceive before a cycle of in vitro fertilization (IVF). In women, normal FSH levels vary with the phase of the menstrual cycle as well as with the age. FSH levels also differ in males from that of females. The normal FSH levels in an adult female who has not yet reached menopause range from 4.7 to 19.5 mIU/ml, depending on where a woman is in her monthly cycle. FSH levels can be measured from a sample of urine or blood collected on day 3 of her menstrual cycle.

FertilitySmarts explains FSH Levels

In females, FSH works in a feedback loop with estrogen. FSH stimulates follicle development within the ovaries and causes these follicles to produce estrogen and release a mature egg during the first half of the menstrual cycle. However, when estrogen levels fall and the egg supply diminishes, more FSH is released from the pituitary gland to help increase the estrogen production. This means that any condition that lowers estrogen levels will raise the FSH levels and vice versa.

Factors that raise the levels of FSH include:

  • Aging: As a woman approaches her late 30s or early 40s, the estrogen levels fall, the quality and quantity of her eggs tend to drops and so does her reproductive potential
  • Menopause, including premature menopause: The FSH levels rise with the onset of menopause due to the shortage of estrogen. The levels then remain consistently elevated to 30 mIU/mL or even higher
  • Premature ovarian failure
  • Pituitary gland tumor
  • Primary ovarian failure secondary to genetic disorders: Low estrogen activity raises FSH

Low FSH levels can be observed with the following

  • Pituitary gland surgery
  • Exposure of the pituitary gland to radiation therapy
  • High prolactin levels: Prolactin is also released from the pituitary but tends to block the production of gonadotropins, including FSH and LH
  • Hypothyroidism: Low thyroid hormone levels trigger the release of another hormone called thyrotropin releasing hormone, which has a stimulating effect on the thyroid as well as the prolactin

Who are the candidates for FSH fertility testing? Elevated FSH levels might indicate a compromised ability of a woman to produce eggs and get pregnant with IVF. Thus, the levels can be used to assess the ovarian reserve (pool of eggs) and predict IVF outcome in a woman who wishes to undergo IVF. This testing is usually done in women who are older than 35 years but have failed to conceive despite continuous attempts for 6 months or in women at higher risk of having a diminished ovarian reserve.

FSH levels are highest during the early phase of the menstrual cycle. Therefore, fertility centers usually measure day 3 (of the menstrual cycle) FSH levels as a component of fertility workup. When FSH levels are high, it does not always indicate that conception is impossible; instead, it may just be challenging but still achievable. This is particularly true in younger women. However, consistently high levels or very high levels might indicate poor IVF outcome, and some fertility centers do not offer IVF to these women.

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