Hirsutism pathophysiology: Difference between revisions
Jump to navigation
Jump to search
Aditya Ganti (talk | contribs) |
Aditya Ganti (talk | contribs) |
||
| Line 23: | Line 23: | ||
*Androgens induce vellus follicles in sex-specific areas to develop into terminal hairs, which are larger and more heavily pigmented. | *Androgens induce vellus follicles in sex-specific areas to develop into terminal hairs, which are larger and more heavily pigmented. | ||
*Hirsutism is caused by increased androgen production and/or an increased sensitivity of the hair follicles to androgens. | *Hirsutism is caused by increased androgen production and/or an increased sensitivity of the hair follicles to androgens. | ||
* | *Hyperandrogenism, resulting from any factors, prolongs the anagen (growth) phase of androgen-sensitive hairs, resulting in their conversion from fine, light, vellus hairs to coarse, dark, terminal hairs. | ||
*The response of hair follicle to androgens and other factors such as local 5 alpha-reductase activity determines the level of conversion of hair from the vellus type to terminal hair.<ref name="pmid10950157">{{cite journal |vauthors=Deplewski D, Rosenfield RL |title=Role of hormones in pilosebaceous unit development |journal=Endocr. Rev. |volume=21 |issue=4 |pages=363–92 |year=2000 |pmid=10950157 |doi=10.1210/edrv.21.4.0404 |url=}}</ref> | *The response of hair follicle to androgens and other factors such as local 5 alpha-reductase activity determines the level of conversion of hair from the vellus type to terminal hair.<ref name="pmid10950157">{{cite journal |vauthors=Deplewski D, Rosenfield RL |title=Role of hormones in pilosebaceous unit development |journal=Endocr. Rev. |volume=21 |issue=4 |pages=363–92 |year=2000 |pmid=10950157 |doi=10.1210/edrv.21.4.0404 |url=}}</ref> | ||
[[image:hairf.png|thumb|center|200px| Hair Follicle<ref name="urlCategory:Hair follicle - Wikimedia Commons">{{cite web |url=https://commons.wikimedia.org/wiki/Category:Hair_follicle#/media/File:Blausen_0437_HairFollicleAnatomy.png |title=Category:Hair follicle - Wikimedia Commons |format= |work= |accessdate=}}</ref> <br> Courtesy to WikiMedia]] | [[image:hairf.png|thumb|center|200px| Hair Follicle<ref name="urlCategory:Hair follicle - Wikimedia Commons">{{cite web |url=https://commons.wikimedia.org/wiki/Category:Hair_follicle#/media/File:Blausen_0437_HairFollicleAnatomy.png |title=Category:Hair follicle - Wikimedia Commons |format= |work= |accessdate=}}</ref> <br> Courtesy to WikiMedia]] | ||
*Growth recommences with the formation of new hair shaft by the reactivation of the [[dermal papillae]], thereby replacing the old hair. | *Growth recommences with the formation of new hair shaft by the reactivation of the [[dermal papillae]], thereby replacing the old hair. | ||
*The hair growth cycle takes months to years to be completed, causing a delay in hair growth response to changes from effects of [[androgens]]. | *The hair growth cycle takes months to years to be completed, causing a delay in hair growth response to changes from effects of [[androgens]]. | ||
Revision as of 18:32, 12 October 2017
|
Hirsutism Microchapters |
|
Diagnosis |
|---|
|
Treatment |
|
Medical Therapy |
|
Case Studies |
|
Hirsutism pathophysiology On the Web |
|
Risk calculators and risk factors for Hirsutism pathophysiology |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: ; Ogheneochuko Ajari, MB.BS, MS [2] Rasam Hajiannasab M.D.[3]
Overview
The growth of sexual hair is dependent on the presence of androgens. Androgens induce vellus follicles in sex-specific areas to develop into terminal hairs, which are larger and more heavily pigmented. [1][2][3][4]
Pathophysiology
Types of Hair
- There are approximately 5 million hair follicles at birth in humans with about 80,000 to 150,000 of them on the scalp.
- The quality of hair is determined by hormones and other intrinsic characteristics of the hair follicle.
- There are various types of hair which include;
- Lanugo hair: The soft hair which covers the fetal skin and it disappears within the first three months after the fetus delivery.
- Vellus hair: This is fine, soft hair that is not pigmented. It covers most of the body before the pubertal period.
- Terminal hair: This is long, coarse and pigmented. Pubertal androgens for example dihydrotestosterone (DHT) convert vellus hair to terminal hair.
Phases of Hair Growth Cycle
- There are 3 phases of hair growth cycle.
- The hair growth phase (termed Anagen phase). This phase varies, depending on the body area affected. It is approximately 4 months for facial hair.
- The involutional phase (Catagen phase). This phase is approximately 2-3 weeks.
- The resting phase (Telogen phase). The hair shaft separates from the dermal papillae at the base of the follicle, which terminates growth.
Pathogenesis
- The growth of sexual hair is dependent on the presence of androgens.
- Androgens induce vellus follicles in sex-specific areas to develop into terminal hairs, which are larger and more heavily pigmented.
- Hirsutism is caused by increased androgen production and/or an increased sensitivity of the hair follicles to androgens.
- Hyperandrogenism, resulting from any factors, prolongs the anagen (growth) phase of androgen-sensitive hairs, resulting in their conversion from fine, light, vellus hairs to coarse, dark, terminal hairs.
- The response of hair follicle to androgens and other factors such as local 5 alpha-reductase activity determines the level of conversion of hair from the vellus type to terminal hair.[1]
Courtesy to WikiMedia
- Growth recommences with the formation of new hair shaft by the reactivation of the dermal papillae, thereby replacing the old hair.
- The hair growth cycle takes months to years to be completed, causing a delay in hair growth response to changes from effects of androgens.
- DHT is a hormone that acts on the hair follicle to produce terminal hair
- Differences in the activity of DHT explains why women with the same plasma level testosterone, have different degrees of hirsutism.
- It is speculated that insulin, at high enough concentration, stimulates the ovarian theca cells to produce androgens.
- There may also be an effect of high levels of insulin to activate the insulin-like growth factor-I (IGF-1) receptor in those same cells resulting in increased androgen production.
References
- ↑ 1.0 1.1 Deplewski D, Rosenfield RL (2000). "Role of hormones in pilosebaceous unit development". Endocr. Rev. 21 (4): 363–92. doi:10.1210/edrv.21.4.0404. PMID 10950157.
- ↑ Messenger AG (1993). "The control of hair growth: an overview". J. Invest. Dermatol. 101 (1 Suppl): 4S–9S. PMID 8326154.
- ↑ Hatch R, Rosenfield RL, Kim MH, Tredway D (1981). "Hirsutism: implications, etiology, and management". Am. J. Obstet. Gynecol. 140 (7): 815–30. PMID 7258262.
- ↑ Labrie F (1991). "Intracrinology". Mol. Cell. Endocrinol. 78 (3): C113–8. PMID 1838082.
- ↑ "Category:Hair follicle - Wikimedia Commons".
