Testosterone

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Também chamado: Total testosterone
Nome formal: Testosterone
Exames relacionados: Follicle stimulating hormone (FSH), Luteneizing hormone (LH), Sex hormone binding globulin (SHBG), Free and bioavailable testosterone (see FAQ section), Dihydrotestosterone (DHT), Estradiol (see Estrogen), Gonadotropin-releasing hormone, Dehydroepiandrosterone sulfate (DHEAS)

De relance

Por que fazer este exame?

To determine abnormal testosterone level in males and females; in males, an abnormal level may help to explain difficulty getting an erection (erectile dysfunction), inability of your partner to get pregnant (infertility), or premature or delayed puberty; in females, to explain the appearance of masculine physical features (virilization), inability to get pregnant, and as a marker for polycystic ovary syndrome (PCOS)

Quando fazer este exame?

If you are male and your doctor thinks that you may be infertile or if you are unable to get or maintain an erection; if you are a boy with either early or delayed sexual maturity; if you are a female but have male traits, such as a low voice or excessive body hair (hirsutism), or have amenorrhea, or are infertile

Amostra:

A blood sample drawn from a vein in your arm

A amostra

O que está sendo pesquisado?

Testosterone is a steroid hormone (androgen) produced by special endocrine tissue (the Leydig cells) in the male testes. Its production is stimulated and controlled by luteinizing hormone (LH), which is manufactured in the pituitary gland. Testosterone works within a negative feedback mechanism: as testosterone increases, LH decreases, whereas increased LH causes decreased testosterone. Testosterone levels are diurnal, peaking in the early morning hours (about 4:00 to 8:00 am), with the lowest levels in the evening (about 4:00 to 8:00 pm). Levels also increase after exercise, but decrease with age. About two-thirds of testosterone circulates in the blood bound to sex-hormone binding protein and slightly less than one-third bound to albumin. A small percent (about 1-4%) circulates as free testosterone.

In males, testosterone stimulates development of secondary sex characteristics, including enlargement of the penis, growth of body hair, muscle development, and a deepening voice. It is present in large amounts in males during puberty and in adult males to regulate the sex drive and maintain muscle mass. Testosterone is also produced by the adrenal glands in both males and females and, in small amounts, by the ovaries in females. In women, testosterone is converted to estradiol, the main sex hormone in females.

Como a amostra é obtida para o exame?

A blood sample is taken by needle from a vein in the arm.

NOTA: Se exames médicos em você ou em alguém importante para você o deixam ansioso ou constrangido, ou se você tem dificuldade de lidar com eles, leia um ou mais dos seguintes artigos: Lidando com dor, desconforto ou ansiedade durante o exame, Conselhos sobre exames de sangue, Conselhos para ajudar crianças durante exames médicos, and Conselhos para ajudar idosos durante exames médicos.

Outro artigo, Siga essa amostra, fornece uma visão da coleta e do processamento de uma amostra de sangue e de uma amostra de cultura da garganta.

É necessário algum preparo para garantir a qualidade da amostra?

No test preparation is needed.

O exame

Perguntas frequentes

Pergunte ao laboratório

* indica um campo necessário



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Fontes do artigo

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NOTA: Este artigo se baseia em pesquisas que incluíram as fontes citadas e a experiência coletiva de Lab Tests Online Conselho de Revisão Editorial. Este artigo é submetido a revisões periódicas do Conselho Editorial, e pode ser atualizado como resultado dessas revisões. Novas fontes citadas serão adicionadas à lista e distinguidas das fontes originais usadas.

Sources Used in Current Review

Pagana K, Pagana T. Mosby's Manual of Diagnostic and Laboratory Tests. 3rd Edition, St. Louis: Mosby Elsevier; 2006, Pp 481-484.

(January 2006) The Hormone Foundation. Low Testosterone and Men’s Health. PDF available for download at http://www.hormone.org/Resources/Reproduction/upload/bilingual_Testosterone.pdf through http://www.hormone.org. Accessed January 2009.

(January 2008) Eugster E, Palmert M, eds. The Hormone Foundation. Precocious Puberty. PDF available for download at http://www.hormone.org/Resources/Growth/upload/bilingual_precocious_puberty.pdf through http://www.hormone.org. Accessed January 2009.

Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER, Bruns DE, eds. St. Louis: Elsevier Saunders; 2006.

(March 18, 2008) Holt E. MedlinePlus Medical Encyclopedia. Testosterone. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003707.htm. Accessed January 2009.

(December 9, 2008) Mayo Clinic. Male hypogonadism. Available online at http://www.mayoclinic.com/health/male-hypogonadism/DS00300 through http://www.mayoclinic.com. Accessed January 2009.

Sources Used in Previous Reviews

Clinical Chemistry: Theory, Analysis, Correlation. 3rd Edition. Lawrence A. Kaplan and Amadeo J. Pesce, St. Louis, MO. Mosby, 1996.

Clinical Chemistry: Principles, Procedures, Correlations. Michael L. Bishop, Janet L. Duben-Engelkirk, Edward P. Fody. Lipincott Williams & Wilkins, 4th Edition.

The Gale Encyclopedia of Childhood and Adolescence: Testosterone. Available online at http://www.findarticles.com/p/articles/mi_g2602 through http://www.findarticles.com.

Laurence M. Demers, PhD. Distinguished Professor of Pathology and Medicine, The Pennsylvania State University College of Medicine, The M. S. Hershey Medical Center, Hershey, PA.