Assignment # 03 - Testosterone function

Testosterone can be found in both males and females.  Testosterone plays an important role during fetal development, puberty and throughout the adult life.  A lack of testosterone in either sex is referred to as “hypogonadism”.

Function & the effects of Hypogonadism

Development

During fetal development, testosterone masculines the brain (by changing into estrogen & crossing the Blood brain barrier) and develops male characteristics of the brain [Mainwarring, 1977].  Hypogonadism during this phase would result in mental retardation, underdeveloped male genitals, or development of female genitalia [Mayo clinic].

Puberty

During puberty testosterone is responsible for increasing muscle mass, adipose tissue, body hair, development of breast tissue (in women), and growth of male genitalia [Mayo clinic].

Hypogonadism can lead to delayed or absent puberty (delayed, underdeveloped or absence of the aforementioned effects of testosterone).

  

Adulthood

during adulthood testosterone is responsible for  Well-being, aggression, cognitive function, bone mineral density and sexual libido in men and women.

 

In women 

Testosterone is involved with greater well-being and with reduced anxiety/depression, puberty and is an important component of female sexuality [Davis, 2001].  In women, testosterone deficiency is characterized by fatigue, and decreases in: motivation, libido, well-being and available “free” Testosterone.  Orally administered estrogen (the pill) can decrease free testosterone by creating more SHBG to bind to the testosterone [Davis, 2001].Hypogonadism in women is less studied, but can be seen after a hysterectomy, injection of exogenous estrogen or during menopause [Davis, 2001].  Testosterone replacement therapy is under investigation for women (methyltestosterone can be prescribed in the United States) [Davis, 2001]. 

In men 

Testosterone is involved with fetal development, mood, aggression, cognitive function, bone mineral density and sexual libido [Howell, 2001].  Hypogonadism in men can result in erectile dysfunction, infertility, fatigue, development of breast tissue, decrease in body hair, bone mass, libido and muscle mass [mayo clinic].  Treatment includes androgen replacement (oral testosterone, intramuscular injections, subcutaneous implants and transdermal therapy) [Howell, 2001].

Hypogonadism

 

Decreased testosterone can cause: 

Lack of libido

Infertilty

Late/absent puberty

Lack of energy

Depression 

Mood swings

 

Treatment can include:

 Hormone replacement therapy

exercise

dietary changes

stress reduction

 

 

Types of Hypogonadism: 

Primary hypogonadism  = Congenital  testicular dysfunction

Develomental problems while still in the womb can cause problems with testosterone production in the testes.  Because the hypothalamus and pituitary are functioning properly, there will be elevated levels of LH & FSH, but still no testosterone production.

Can be due to:

FSH and LH receptor mutations

Cryptorchidism

Myotonic dystrophy

Klinefelter's syndrome: A male who has an extra X chromosome. The most common genotype is XXY.  There will be a problem with testosterone production by the testes.

 

Secondary hypogonadism =  Aquired  hypothalamic-pituitary dysfunction

The hypothalamus and pituitary are not functioning correctly.  Low levels of LH & FSH will cause no signal to the testes to produce the testosterone.  

Can be due to:

-aging (called "andropause" in men).

-pituitary tumours

-ingestion of drugs

-head trauma

 

References

Davis, S. (2001) Testosterone deficiency in women. The Journal of reproductive medicine. Vol 46. Pg 291-296

Howell, S (2001) Testosterone deficiency and replacement. Hormone research, vol 56, pg 86

  

Mainwaring, W.I.P (1977) The Mechanism of Action of Androgens.  Springer-Verlag New York Inc. pg.32-41

Websites

 

Mayo clinic (2010) Mayo Foundation for Medical Education and Research (MFMER). found at www.mayoclinic.com

(2006) Cecil Texbook of Medicine found at: http://enotes.tripod.com/hypogonadism.htm