It is the main male sex hormone, belonging to the category of androgens. During puberty, testosterone stimulates the development of spermatozoa in the testes and primary and secondary male sexual characteristics, causing the growth of the genital organs, beard and pubic hair and the change of voice.
It is mainly produced in the Leydig cells of the testes, under the influence of the luteinizing hormone (LH) released by the anterior pituitary gland. In women, however, it is a product of the transformation of another hormone produced by the adrenals and ovaries.
What is it for
In humans, the drop in testosterone indicates an insufficiency of the gonads, which may be due to insufficiency of the pituitary gland or tumor of the hypothalamus (two endocrine glands), with lowering of the follicle-stimulating and luteinizing hormones, or to peripheral damage (orchitis, castration, etc.), with an increase in the other two hormones. In women, the dosage of testosterone (associated with that of other hormones) serves to establish the cause of hirsutism.
An increase in testosterone is present in idiopathic precocious puberty or caused by lesions of the central nervous system, in adrenal tumors or in congenital adrenal hyperplasia. The highest levels are found in the early hours of the morning. Decreased levels or at low normal limits are found in cirrhosis of the liver, during estrogen therapy, in marked obesity, in association with high levels of LH, in renal failure and in malnutrition.
How the exam takes place
The examination is carried out on a blood sample. All medications that can affect plasma testosterone levels (based on thyroid extracts, GH, testosterone, and estrogen) must be stopped 72 hours before the test. Fasting before sampling is not strictly necessary, although a lipemic serum may interfere with the results of the assay.
In humans before development normal values vary from 0.1 to 5 ng/ml of blood; in adult men they range from 3.5 to 7.5 ng / ml of blood; in the elderly with more than 60 years from 1 to 5 ng/ml. In women, normal values vary in the follicular phase from 0.25 to 0.35 ng / ml; in the preovulatory phase from 0.33 to 0.47 ng / ml; in the lutein phase esteroides comprar from 0.30 to 0.40 ng / ml; in menopause from 0.25 to 0.35 ng / ml.