Follicle-stimulating hormone

Source: Wikipedia, the free encyclopedia.
Chr. 6 q14-q21
Search for
StructuresSwiss-model
DomainsInterPro
Chr. 11 p13
Search for
StructuresSwiss-model
DomainsInterPro

Follicle-stimulating hormone (FSH) is a

anterior pituitary gland[2] and regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and luteinizing hormone (LH) work together in the reproductive system.[3]

Structure

FSH is a 35.5 kDa

N-acetylglucosamine, galactose, and sialic acid
.

Genes

In humans, the gene for the

activin.[citation needed
]

Activity and functions

FSH regulates the development, growth, pubertal maturation and reproductive processes of the human body.[8]

Control of FSH release from the pituitary gland is unknown. Low frequency gonadotropin-releasing hormone (GnRH) pulses increase FSH mRNA levels in the rat,[9] but is not directly correlated with an increase in circulating FSH.[10] GnRH has been shown to play an important role in the secretion of FSH, with hypothalamic-pituitary disconnection leading to a cessation of FSH. GnRH administration leads to a return of FSH secretion. FSH is subject to oestrogen feed-back from the gonads via the hypothalamic pituitary gonadal axis.

Reference ranges for the blood content of follicle-stimulating hormone levels during the menstrual cycle.[11]
- The ranges denoted By biological stage may be used in closely monitored menstrual cycles in regard to other markers of its biological progression, with the time scale being compressed or stretched to how much faster or slower, respectively, the cycle progresses compared to an average cycle.
- The ranges denoted Inter-cycle variability are more appropriate to use in non-monitored cycles with only the beginning of menstruation known, but where the woman accurately knows her average cycle lengths and time of ovulation, and that they are somewhat averagely regular, with the time scale being compressed or stretched to how much a woman's average cycle length is shorter or longer, respectively, than the average of the population.
- The ranges denoted Inter-woman variability are more appropriate to use when the average cycle lengths and time of ovulation are unknown, but only the beginning of menstruation is given.

Effects in females

FSH stimulates the growth and recruitment of immature

Inhibin B to lower FSH serum levels.[citation needed
]

In addition, there is evidence that gonadotropin surge-attenuating factor produced by small follicles during the first half of the follicle phase also exerts a negative feedback on pulsatile luteinizing hormone (LH) secretion amplitude, thus allowing a more favorable environment for follicle growth and preventing premature luteinization.[12]

As a woman nears perimenopause, the number of small antral follicles recruited in each cycle diminishes and consequently insufficient Inhibin B is produced to fully lower FSH and the serum level of FSH begins to rise. Eventually, the FSH level becomes so high that

downregulation of FSH receptors occurs and by postmenopause any remaining small secondary follicles no longer have FSH nor LH receptors.[13]

When the follicle matures and reaches 8–10 mm in diameter it starts to secrete significant amounts of

GnRH pulses occur and an LH
surge results.

The increase in serum

GnRH production in the hypothalamus.[14]

The decrease in serum FSH level causes the smaller follicles in the current cohort to undergo atresia as they lack sufficient sensitivity to FSH to survive. Occasionally two follicles reach the 10 mm stage at the same time by chance and as both are equally sensitive to FSH both survive and grow in the low FSH environment and thus two ovulations can occur in one cycle possibly leading to non-identical (

dizygotic) twins.[citation needed
]

Effects in males

FSH stimulates primary

spermatocytes to undergo the first division of meiosis
, to form secondary spermatocytes.

FSH enhances the production of

basolateral membranes,[15] and is critical for the initiation of spermatogenesis
.

Measurement

Follicle-stimulating hormone is typically measured in the early follicular phase of the menstrual cycle, typically day three to five, counted from last menstruation. At this time, the levels of estradiol (E2) and progesterone are at the lowest point of the menstrual cycle. FSH levels in this time is often called basal FSH levels, to distinguish from the increased levels when approaching ovulation.[16]

FSH is measured in

international units (IU). For Human Urinary FSH, one IU is defined as the amount of FSH that has an activity corresponding to 0.11388 mg of pure Human Urinary FSH.[17] For recombinant FSH, one IU corresponds to approximately 0.065 to 0.075 µg of a "fill-by-mass" product.[18]
The mean values for women before ovulation are around (3.8-8.8) IU/L. After ovulation these levels drop to between (1.8-5.1) IU/L. At the mid of the menstrual cycle it reaches its highest value, between (4.5-22.5) IU/L. During menopause, the values goes up even more, between (16.74-113.59) IU/L. For men, the mean values are around (16.74-113.59) IU/L.

Disease states

FSH levels are normally low during

childhood and, in females, high after menopause
.

High FSH levels

The most common reason for high serum FSH concentration is in a female who is undergoing or has recently undergone menopause. High levels of FSH indicate that the normal restricting feedback from the gonad is absent, leading to an unrestricted pituitary FSH production. FSH may contribute to postmenopausal osteoporosis and cardiovascular disease.[19]

If high FSH levels occur during the reproductive years, it is abnormal. Conditions with high FSH levels include:

  1. Premature menopause
    also known as premature ovarian failure
  2. Poor ovarian reserve also known as premature ovarian aging
  3. Gonadal dysgenesis, Turner syndrome, Klinefelter syndrome
  4. Castration
  5. Swyer syndrome
  6. Certain forms of congenital adrenal hyperplasia
  7. Testicular failure
  8. Lupus[20]

Most of these conditions are associated with subfertility or infertility. Therefore, high FSH levels are an indication of subfertility or infertility.

Low FSH levels

Diminished secretion of FSH can result in failure of gonadal function (hypogonadism). This condition is typically manifested in males as failure in production of normal numbers of sperm. In females, cessation of reproductive cycles is commonly observed.[citation needed] Conditions with very low FSH secretions are:

  1. Polycystic Ovarian Syndrome[21]
  2. Polycystic ovarian syndrome
    + obesity + hirsutism + infertility
  3. Kallmann syndrome
  4. Aromatase excess syndrome
  5. Hypothalamic suppression
  6. Hypopituitarism
  7. Hyperprolactinemia
  8. Gonadotropin deficiency
  9. Gonadal suppression therapy
    1. GnRH antagonist
    2. downregulation
      ).

Isolated FSH deficiency due to mutations in the gene for β-subunit of FSH is rare with 13 cases reported in the literature up to 2019.[22]

Use as therapy

Further information: Gonadotropin preparations, Controlled ovarian hyperstimulation, and Ovulation induction

FSH is used commonly in infertility therapy, mainly for

IVF. In some cases, it is used in ovulation induction for reversal of anovulation
as well.

FSH is available mixed with LH activity in various

Menopur
, as well as without LH activity as recombinant FSH (Gonapure, Gonal F, Follistim, Follitropin alpha).

Potential role in vascularization of solid tumors

Elevated FSH receptor levels have been detected in the endothelia of tumor vasculature in a very wide range of solid tumors. FSH binding is thought to upregulate neovascularization via at least two mechanisms – one in the

avastin for current anti-VEGF approaches).[23]

See also

  • EFSH, a follicle-stimulating hormone obtained from equine species

References

  1. PMID 25767463
    .
  2. ^ "Follicle-Stimulating Hormone". WebMD.
  3. ^ Bowen R. "Luteinizing and Follicle Stimulating Hormones". www.vivo.colostate.edu. Retrieved 2019-05-06.
  4. PMID 6267989
    .
  5. ^ "CGA glycoprotein hormones, alpha polypeptide [Homo sapiens (human)]". NCBI. Retrieved 2 January 2016.
  6. PMID 22802634
    .
  7. ^ Online Mendelian Inheritance in Man (OMIM): CHORIONIC GONADOTROPIN, ALPHA CHAIN; CGA - 118850
  8. PMID 29982321
    .
  9. PMID 9927322
    .
  10. PMID 22423050
    .
  11. ISSN 2002-4436
    .
  12. PMID 14748688
    .
  13. PMID 8865134
    .
  14. ISBN 978-0-07-147899-1
    .
  15. ISBN 978-1-4160-2328-9
    .
  16. ^ "FSH". labtestsonline.org. Retrieved 2019-05-06.
  17. ^ World Health Organization Technical Report Series N0. 565. WHO Expert Committee on Biological Standardization. Twenty-sixth Report. World Health Organization. Geneva. 1975
  18. PMID 19007609
    .
  19. S2CID 51602238
    .
  20. PMID 16320320
    .
  21. ^ "Polycystic ovary syndrome: MedlinePlus Medical Encyclopedia". medlineplus.gov. Retrieved 2019-05-06.
  22. ^ Misgar RA, Wani AI, Bankura B, Bashir MI, Roy A, Das M (2019) FSH β-subunit mutations in two sisters: the first report from the Indian sub-continent and review of previous cases. Gynecol Endocrinol 2:1-4
  23. PMID 20961245
    .

External links

Wikimedia Commons has media related to Follicle-stimulating hormone.
  • FSH - Lab Tests Online
Retrieved from "https://en.wikipedia.org/w/index.php?title=Follicle-stimulating_hormone&oldid=1216306486"