FSH

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Also known as: Follicle-stimulating Hormone
Formal name: Follicle-stimulating Hormone, serum

At a Glance

Why Get Tested?

To evaluate your pituitary function, especially as it relates to fertility issues, gonadal failure, maturation concerns, or pituitary tumors

When to Get Tested?

When you are having difficulty getting pregnant or are having irregular menstrual periods; when your doctor thinks that you have symptoms of pituitary or hypothalamic disorders or symptoms of ovarian or testicular disease; or when a doctor suspects that a child has delayed or earlier than expected sexual maturation

Sample Required?

A blood sample drawn from a vein in your arm; sometimes a random urine sample or 24-hour urine collection may be taken

Test Preparation Needed?

None

The Test Sample

What is being tested?

Follicle-stimulating hormone (FSH) is made by the pituitary gland in the brain. Control of FSH production is a complex system involving hormones produced by the gonads (ovaries or testes), the pituitary, and the hypothalamus.

In women, FSH stimulates the growth and maturation of eggs (follicles) in the ovaries during the follicular phase of the menstrual cycle. The menstrual cycle is divided into the follicular and the luteal phases, characterized by a mid-cycle surge of FSH and luteinizing hormone (LH). Ovulation occurs shortly after this mid-cycle surge of hormones. During the follicular phase, FSH initiates the production of estradiol by the follicle, and the two hormones work together in the further development of the egg follicle. During the luteal phase, FSH stimulates the production of progesterone. Both estradiol and progesterone help the pituitary control the amount of FSH produced. FSH also facilitates the ability of the ovary to respond to LH. At the time of menopause, the ovaries stop functioning and FSH levels rise. 

In men, FSH stimulates the testes to produce mature sperm and also promotes the production of androgen binding proteins. FSH levels are relatively constant in males after puberty.

In infants and children, FSH levels rise shortly after birth and then fall to very low levels by 6 months in boys and 1-2 years in girls. Concentrations begin to rise again before the beginning of puberty and the development of secondary sexual characteristics.

How is the sample collected for testing?

A blood sample is drawn by needle from a vein in the arm. Sometimes, a random urine sample is collected but, due to the cyclic secretion of FSH, a 24-hour collection of urine may be requested. By measuring FSH levels produced over a 24-hour period, the variation in FSH levels seen through out the day can be minimized.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is required, but a woman's sample should be collected at specific times during her menstrual cycle.

The Test

Common Questions

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

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Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 412-416.

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Jabbour, S. (Updated 2009 June 15). Follicle-Stimulating Hormone Abnormalities. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/118810-overview through http://emedicine.medscape.com. Accessed February 2010.

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MayoClinic.com: Menopause. Available online at http://www.mayoclinic.com/health/menopause/DS00119 through http://www.mayoclinic.com. Accessed February 2010.

National Institute on Aging: Menopause. Available online at http://www.nia.nih.gov/HealthInformation/Publications/menopause.htm through http://www.nia.nih.gov. Accessed February 2010.

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Sources Used in Previous Reviews

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Blondell RD, Foster MB, Kamlesh CD. Disorders of Puberty. American Family Physician, July 1999 (online publication). Available online at http://www.aafp.org/afp/990700ap/209.html through http://www.aafp.org.

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Laurence M. Demers, PhD. Distinguished Professor of Pathology and Medicine, The Pennsylvania State University College of Medicine, The M. S. Hershey Medical Center, Hershey, PA.

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