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Lab Test: Follicle Stimulating Hormone, FSH Level

    Lab Test
    • Follicle stimulating hormone (FSH)
    Description
    • Measurement of follicle stimulating hormone (FSH) level in serum for the evaluation and management of endocrine disorders and in determination of menopause.
    Reference Range
    • Female, menstruating:
      • Follicular phase:  3-20 milli-International Units/mL (3-20 international Units/L)
      • Ovulatory phase:  9-26 milli-International Units/mL (9-26 International Units/L)
      • Luteal phase:  1-12 milli-International Units/mL (1-12 International Units/L)
    • Postmenopausal:  18-153 milli-International Units/mL (18-153 International Units/L)
    • Male:  1-12 milli-International Units/mL (1-12 International Units/L)
    • Female 2-11 months:  0.10-11.3 milli-International Units/mL (0.19-11.3 International Units/L)
    • Male 2-11 months:  0.19-11.3 milli-International Units/mL (0.19-11.3 International Units/L)
    • Female 1-10 years:  0.68-6.7 milli-International Units/mL (0.68-6.7 International Units/L)
    • Male 1-10 years:  0.3-4.6 milli-International Units/mL (0.3-4.6 International Units/L)
    • Puberty, Tanner stages (TS):
      • TS 1-2 Male:  0.3-4.6 milli-International Units/mL (0.3-4.6 International Units/L)
      • TS 3-4 Male:  1.24-15.4 milli-International Units/mL (1.24-15.4 International Units/L)
      • TS 5 Male:  1.53-6.8 milli-International Units/mL (1.53-6.8 International Units/L)
    Indications & Uses
    • Primary or secondary amenorrhea - Low FSH levels indicate hypogonadotropic hypogonadism or hypothalamic dysfunction.  In these disorders, gonadotropin-releasing hormone secretion is very low, which results in low levels of FSH, luteinizing hormone, and estradiol. 
      • A FSH level in the castrate range (>30 International Units/L) in combination with a low estradiol level (< 60 pmol/L) is diagnostic of ovarian failure or, rarely, resistant ovary syndrome.
      • About 30% of women with secondary amenorrhea have normal levels of gonadotropins.
    • Suspected hypogonadism
      • Men:
        • Increased levels of serum FSH and luteinizing hormone (LH) suggest primary testicular failure.
        • The diagnosis of hypogonadism is first suggested by a decrease in sperm count or testosterone, and is confirmed by elevated gonadotropin levels. 
        • After puberty onset, men with Klinefelter syndrome have uniformly elevated FSH and LH levels, regardless of the serum testosterone level.  Before puberty onset, the FSH, LH, and testosterone levels are normal. 
        • An isolated increase in FSH levels with normal LH and testosterone levels suggests failure of the testicular germ cell compartment. 
      • Women:
        • If obtained during the early follicular phase, FSH levels greater than 10 International Units/L indicate reduced ovarian reserve, and levels greater than 40 International Units/L indicate ovarian failure.
    • Decreased pituitary follicle stimulating hormone -
      • Men:
        • Patients with low or normal FSH and LH levels and low testosterone levels, are categorized as having hypogonadotropic hypogonadism.  Men with a selective decrease of LH and FSH without any apparent cause, and with normal function of the other pituitary hormones, are categorized as having isolate gonadotropin deficiency or idiopathic hypogonadotropic hypogonadism. 
        • In Kallman syndrome (classic hypogonadotropic hypogonadism) FSH, testosterone and LH levels will be low.
      • Women:
        • In the early follicular phase, FSH levels less than 5 International Units/L suggest hypothalamic or pituitary dysfunction.
        • FSH, LH, and estradiol levels in women with hypogonadotropic hypogonadism will be low, regardless of the cause. 
        • Men with azoospermia and normal FSH, LH and testosterone levels may have an obstructive lesion requiring further evaluation. 
    • Suspected menopause - the cutoff value of 40 International Units/L is not independently useful for clinical determination of postmenopausal women.  In women aged 45 to 55 years without a uterus or hot flashes, FSH levels >30 International Units/L suggest menopause. 
    • Suspected premature ovarian failure - characterized by elevated FSH levels before the age of 40, and is the result of premature depletion of the oocyte-follicle complex. 
    • To predict ongoing pregnancy rates for assisted reproductive procedures - cutoff values used to test ovarian reserve, range from 10 to 25 milli-International Units/mL; variations are due to laboratory factors, such as laboratory technique and, reference standards.
      • A high basal FSH level identifies women who are very unlikely to have an ongoing pregnancy after in vitro fertilization.
    Clinical Application

    FSH is a glycoprotein produced in the anterior pituitary gland in response to stimulation by gonadotropin-releasing hormone (GNRH), previously called luteinizing-releasing hormone.  GNRH is stimulated when circulating levels of estrogen (in females) or testosterone (in males) are low.  Through a feedback mechanism, GNRH is stimulated by the hypothalamus, which in turn stimulates the production and release of FSH.   FSH, along with LH, then acts on the ovary or testes.  In females, FSH stimulates the development of follicles in the ovary.  In the male, FSH stimulates Sertoli cell development.  In the end, estrogen or testosterone is produced, which in turn inhibits FSH.  FSH is necessary for maturation of the ovaries and testes and necessary for sperm production. 

    Because FSH levels vary throughout the day and during different phases of the menstrual cycle, clinical assessment may require pooled or multiple serial blood specimens.  However, a single specimen is often sufficient in persons with high gonadotropin levels (e.g., anarchism or postmenopausal women). 

    Increased levels may indicate:

    Gonadal failure (e.g., physiologic menopause, ovarian dysgenesis [Turner syndrome], testicular dysgenesis [Klinefelter syndrome], castration, anorchia, hypogonadism, polycystic ovaries, complete testicular feminization syndrome), precocious puberty, pituitary adenona, or alcoholism. 

    Decreased levels may indicate:

    Pituitary failure, hypothalamic failure, stress anorexia nervosa, malnutrition, hemochromatosis, anorexia nervosa, pregnancy, severe illness, hyperprolactinemia, or sickle cell disease.

    Drug-Lab Interactions
    • Recent use of radioisotopes may affect results if the testing method is performed by radioimmunoassay.
    • Drugs that may increase FSH levels include:  anticonvulsants, cimetidine, clomiphene, digitalis, levodopa, naloxone, and spironolactone.
    Test Tube Needed
    • Red top tube
    Procedure
    • Collect 7 mL of venous blood. 
    • Indicate the date of the last menstrual period on the laboratory slip.  Note if the woman is postmenopausal. 
    • Apply pressure or a pressure dressing to the venipuncture site and assess the site for bleeding.
    Storage and Handling
    • Store refrigerated or frozen.  Stable for 8 days at room temperature and for 14 days at 4°C
    What To Tell Patient Before & After
    • Explain the procedure to the patient.
    • Tell the patient that no food or fluid restrictions are needed.
    References
    • LaGow B et al., eds. PDR Lab Advisor. A Comprehensive Point-of-Care Guide for Over 600 Lab Tests.  First ed. Montvale, NJ: Thomson PDR; 2007.
    • Pagana K, Pagana TJ eds. Mosby's Manual of Diagnostic and Laboratory Tests. 5th Ed.  St. Louis, Missouri. 2014.

MESH Terms & Keywords

  • Follicle, Stimulating, Hormone, FSH Level