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An Introduction to FSH

MVSAT 2024

The central neuroendocrine regulator of the hypothalamic-pituitary-gonadal axis is gonadotropin-releasing hormone (GnRH). The two gonadotropic hormones that are secreted by the pituitary gland's gonadotropic cells and are induced by gonadotropin-releasing hormones are luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The hypothalamus produces GnRH, which is then sent to the pituitary gland through circulation.

What is FSH?

A hormone that is produced by the anterior lobe of the pituitary gland and that is responsible for stimulating the growth of ovum-containing follicles in the ovary as well as activating cells that are responsible for sperm formation.

Function of FSH

Human sexual development and functions are significantly influenced by FSH. Children often have low FSH levels, which rise once puberty begins. FSH levels increase during puberty, causing the testicles to secrete testosterone and the ovaries to secrete estrogen. The numerous consequences that puberty has on the body are caused by these first alterations.

  • The menstrual cycle causes changes in FSH levels. FSH is essential for promoting follicular growth so that ovulation can take place.

  • The time between the first day of menstruation and ovulation is known as the follicular phase of the menstrual cycle. Several follicles inside the ovaries are stimulated by FSH during this stage, which causes them to begin maturing. The first week of this period is when FSH levels are at their peak.

  • Until one follicle takes control, the other growing follicles compete for dominance. This follicle then starts to emit estradiol and inhibin, which stop the release of FSH. Ovulation results from the confluence of an LH peak and the maximum FSH concentration.

  • The remaining follicles that did not become dominant, deteriorate and perish as a result of the fall in FSH levels. During the luteal phase, FSH stays low, preventing the maturation of fresh follicles.

  • It is understandable why abnormal FSH levels are frequently linked to infertility because FSH is so important for follicle formation and ovulation. Changes in the menstrual cycle, poor male sex drive, and delayed or early puberty can all be attributed to FSH.

  • Additionally, FSH increases sperm production. Men's FSH levels often remain consistent, in contrast to women's, which vary depending on the phases of the menstrual cycle.

FSH Levels Chart

FSH normal range will differ, depending on a person's age and sex. The results of the FSH test normal range show the following values:


  • Before puberty: 0 to 5.0 mIU/mL (0 to 5.0 IU/L)

  • During puberty: 0.3 to 10.0 mIU/mL (0.3 to 10.0 IU/L)

  • Adult: 1.5 to 12.4 mIU/mL (1.5 to 12.4 IU/L)


  • Before puberty: 0 to 4.0 mIU/mL (0 to 4.0 IU/L)

  • During puberty: 0.3 to 10.0 mIU/mL (0.3 to 10.0 IU/L)

  • Women who are menstruating: 4.7 to 21.5 mIU/mL (4.5 to 21.5 IU/L)

  • After menopause: 25.8 to 134.8 mIU/mL (25.8 to 134.8 IU/L)

Low FSH Levels Symptoms

Throughout the menstrual cycle, FSH levels might change and often peak just before ovulation. However, some women may have persistently low FSH levels, which might cause the following symptoms:

  • A hot flash

  • No or irregular periods

  • Pubic hair loss

  • Inability to breastfeed due to lack of milk production

FSH Test

The follicle-stimulating hormone (FSH) level in your blood is measured by an FSH blood test. Your pituitary gland, a little gland situated beneath the brain, produces FSH. The growth and operation of the sexual organs are significantly influenced by FSH.

FSH LH Prolactin Test: This examination focuses on the hormones that impact a woman's fertility. When infertility occurs, it is also done to ascertain the hormonal factors. Once the range of the hormones is understood, the doctor will next recommend a course of treatment. The four major reproductive hormones—FSH (Follicle-stimulating hormone), LH (Luteinizing Hormone), Prolactin, and TSH (Thyroid-stimulating Hormone)—help a woman get pregnant and maintain general health. Conception requires the precise presence of each hormone at a specific time of the menstrual cycle, in a specific amount.

Certain female reproductive issues are treated with FSH injection (Urofollitropin). It offers the hormone (FSH) which is necessary for the ovaries to start producing eggs. For the growth and release of a mature egg, this medicine is typically combined with another hormone (hCG) (ovulation). Women whose ovaries are no longer producing eggs adequately are not advised to take this medicine (primary ovarian failure).


The article gives an insight into important topics like functions of FSH, variation of FSH levels in different genders, and FSH test. FSH levels fluctuate depending on gender and age. They also change depending on the stage of the woman's menstrual cycle that she is currently in. The FSH test may be used with additional assessments of a woman's ovarian reserve that consider her levels of luteinizing hormone, estradiol, and progesterone.

The ability of a woman to become pregnant as she ages is referred to as the "ovarian reserve." The chances of getting pregnant may be lower than anticipated for your age if one has a high FSH level. This does not imply that an individual will never be able to conceive, but they may experience greater difficulty and require infertility therapy.

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1. What is the mechanism of hormone action?

By attaching to specific proteins called hormone receptors found only in the target tissues, hormones affect the target tissues. Target cell hormone receptors that are attached to the cell membrane are referred to as membrane-bound receptors, whereas intracellular receptors, primarily nuclear receptors, are located inside the target cell (present in the nucleus). A hormone-receptor complex is created when a hormone binds to its receptor. Since each receptor exclusively recognises one hormone, receptors are particular. The development of the hormone-receptor complex causes specific biochemical alterations in the target tissue.

2. What are high FSH levels?

The body requires more FSH to promote the maturation of eggs and ovulation if FSH levels are unusually high. This could mean that the eggs in the ovaries are of subpar quality and quantity. This is a typical aspect of ageing and affects women more frequently after the age of 38. However, elevated FSH levels can occur in even young women. For instance, if a woman in her 20s has primary ovarian insufficiency, her FSH levels may be high (premature ovarian failure).

3. What is the difference between FSH and LH?

FSH causes the ripening of the egg inside a follicle in the female body. One of the two ovaries of a woman releases one egg each month. The follicle, a bag filled with fluid, houses these eggs. FSH or follicle-stimulating hormone helps in the maturing of the egg inside the follicle.

LH or luteinizing hormone comes into play once the egg is mature inside the follicle. A surge of LH hormones causes the release of this egg from inside the ovary. Once the egg is released, the rest of the follicle starts secreting progesterone and some estrogens. 

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