FOLLICLE STIMULATING HORMONE (FSH)
Follicle-stimulating hormone (FSH) is a hormone found in humans and other animals. It is synthesized and secreted by gonadotrophs of the anterior pituitary gland. FSH regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and Luteinizing hormone (LH) act synergistically in reproduction.
Structure:-FSH is a glycoprotein. Each monomeric unit is a protein molecule with a sugar attached to it; two of these make the full, functional protein. Its molecular weight is about 30,000kd.
Structure:-FSH is a glycoprotein. Each monomeric unit is a protein molecule with a sugar attached to it; two of these make the full, functional protein. Its molecular weight is about 30,000kd.
FUNCTIONS:-
1.In Males -
In males, FSH induces Sertoli cells to secrete inhibin and stimulates the formation of sertoli-sertoli tight junctions (zonula occludens).
FSH stimulates primary spermatocytes to undergo the first division of meiosis, to form secondary spermatocytes.
FSH enhances the production of androgen-binding protein by the Sertoli cells of the testes by binding to FSH receptors on their basolateral membranes, and is critical for the initiation of spermatogenesis
2.In Females-
In females, FSH initiates follicular growth, specifically affecting granulosa cells. With the concomitant rise in inhibin B, FSH levels then decline in the late follicular phase. This seems to be critical in selecting only the most advanced follicle to proceed to ovulation. At the end of the luteal phase, there is a slight rise in FSH that seems to be of importance to start the next ovulatory cycle.
REGULATION:-
Normal Results-
Normal FSH levels will differ depending on a person's age and gender.
* mIU/ml = milli international units per milliliter
DISEASE SATES-
1.LOW LEVEL-
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. Conditions with very low FSH secretions are:
2.HIGH 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 Follicle-Stimulating Hormone indicate that the normal restricting feedback from the gonad is absent, leading to an unrestricted pituitary FSH production.
If high FSH levels occur during the reproductive years, it is abnormal. Conditions with high FSH levels include:
1.In Males -
In males, FSH induces Sertoli cells to secrete inhibin and stimulates the formation of sertoli-sertoli tight junctions (zonula occludens).
FSH stimulates primary spermatocytes to undergo the first division of meiosis, to form secondary spermatocytes.
FSH enhances the production of androgen-binding protein by the Sertoli cells of the testes by binding to FSH receptors on their basolateral membranes, and is critical for the initiation of spermatogenesis
2.In Females-
In females, FSH initiates follicular growth, specifically affecting granulosa cells. With the concomitant rise in inhibin B, FSH levels then decline in the late follicular phase. This seems to be critical in selecting only the most advanced follicle to proceed to ovulation. At the end of the luteal phase, there is a slight rise in FSH that seems to be of importance to start the next ovulatory cycle.
REGULATION:-
- Uses cAMP secondary messenger system.
- FSH is under the control of the GnRH of the hypothalamus. GnRH is a decapeptide which has pulsatile secretion.
- It is also regulated by the feedback effect of estrogen and progesterone(females) and testosterone in males.
- Inhibin secreted by corpus leuteum in females and sertoli cells in males inhibits secretion. [B1] & [B2]
Normal Results-
Normal FSH levels will differ depending on a person's age and gender.
- Male
- Before puberty: 0 - 5.0 mIU/ml*
- During puberty: 0.3 - 10.0 mIU/ml
- Adult: 1.5 - 12.4 mIU/ml
- Female:
- Before puberty: 0 - 4.0 mIU/ml
- During puberty: 0.3 - 10.0 mIU/ml
- Women who are menstruating: 4.7 - 21.5 mIU/ml
- Postmenopausal: 25.8 - 134.8 mIU/ml
* mIU/ml = milli international units per milliliter
DISEASE SATES-
1.LOW LEVEL-
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. Conditions with very low FSH secretions are:
- Polycystic Ovarian Syndrome
- Polycystic Ovarian Syndrome + Obesity + Hirsutism + Infertility
- Kallmann syndrome
- Hypothalamic suppression
- Hypopituitarism
- Hyperprolactinemia
- Gonadotropin deficiency
2.HIGH 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 Follicle-Stimulating Hormone indicate that the normal restricting feedback from the gonad is absent, leading to an unrestricted pituitary FSH production.
If high FSH levels occur during the reproductive years, it is abnormal. Conditions with high FSH levels include:
- Premature menopause also known as Premature Ovarian Failure
- Poor ovarian reserve also known as Premature Ovarian Aging
- Gonadal dysgenesis, Turner syndrome
- Castration
- Swyer syndrome
- Certain forms of CAH [16]