At a Glance
Why Get Tested?
In children, to evaluate early or delayed sexual maturation (puberty)
When to Get Tested?
For women, when you are having difficulty getting pregnant or are having irregular or absence of menstrual periods
For men, when your partner cannot get pregnant, or you have a low sperm count, low muscle mass or decreased sex drive
When a health practitioner suspects that a child has delayed or earlier than expected sexual maturation
Test Preparation Needed?
None, but the timing of a woman's sample will be correlated with her menstrual cycle.
The Test Sample
What is being tested?
Follicle-stimulating hormone (FSH) is a hormone associated with reproduction and the development of eggs in women and sperm in men. This test measures FSH in the blood or urine.
FSH is made by the pituitary gland, a grape-sized organ located at the base of the brain. Control of FSH production is a complex system involving the hypothalamus in the brain, the pituitary gland, and the hormones produced by the ovaries or testicles. The hypothalamus releases gonadotropin-releasing hormone (GnRH), which stimulates the pituitary to release FSH and luteinizing hormone (LH), a closely related hormone also involved in reproduction.
- 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, with each phase lasting about 14 days. During this 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. Near the end of the follicular phase, there is a surge of FSH and luteinizing hormone. Release of the egg from the ovary (ovulation) occurs shortly after this surge of hormones. The hormone inhibin as well as estradiol and progesterone help control the amount of FSH released by the pituitary gland. FSH also facilitates the ability of the ovary to respond to LH.
As a woman ages and menopause approaches, ovarian function wanes and eventually ceases. As this occurs, FSH and LH levels rise.
- In men, FSH stimulates the testicles to produce mature sperm and also promotes the production of androgen binding proteins. FSH levels are relatively constant in men 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.
Disorders affecting the hypothalamus, pituitary, and/or the ovaries or testicles can cause the production of too much or too little FSH, resulting in a variety of conditions such as infertility, abnormal menstrual cycles, or early (precocious) or delayed sexual maturation (puberty).
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 throughout 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 needed, but a woman's sample should be collected at specific times during her menstrual cycle.
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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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