Description
Testosterone, Total - is the most potent, naturally secreted androgen. In postpubertal males, testosterone is secreted primarily by the testes with only a small amount derived from peripheral conversion of androstenedione. In adult women, it has been estimated that over 50 percent of serum testosterone is derived from the peripheral conversion of androstenedione secreted by the adrenal gland and ovary. The remainder is from the direct secretion of testosterone from these glands. The majority of circulating testosterone is bound by sex hormone binding globulin (SHBG). A smaller portion is bound by albumin. Only 1-2 percent exists in the circulation as free or unbound testosterone.
More Information:
Testosterone is a steroid hormone. It is made by the testes in males. Its production is controlled by luteinizing hormone (LH), which is manufactured in the pituitary gland. In males, testosterone stimulates development of secondary sex characteristics. Testosterone is also produced by the adrenal glands in both males and females and by the ovaries in females. In women, testosterone is converted to estradiol, the main sex hormone in females.
Testosterone testing is used to diagnose various conditions, including :
• delayed or precocious puberty in boys
• decreased sex drive in men
• erectile dysfunction
• infertility in bohth men and women
• testicular tumors
• hirsutism and masculinization, also called virilization in women
Its concentration is measured by means of analysis of a blood sample drawn from the vein in the arm.
Purpose of the test
To meassure the testosterone levels in blood in order to help explain symptoms such difficulty getting an erection in men, inability of women to get pregnant, premature or delayed puberty in men, or the appearance of masculine physical features in female.
In boys, the test is ordered, often along with the FSH and LH tests, if puberty is delayed or slow in developing.
In men, the test can be ordered when infertility is suspected or if the patient has a decreased erectile dysfunction.
In women, testosterone testing may be done if a patient has irregular or no menstrual periods, is having difficulty getting pregnant, or appears to have masculine features, such as facial and body hair, male pattern baldness, and a low voice. Testosterone levels can rise because of tumors that develop in either the ovary or adrenal gland or because of other conditions, such as polycystic ovarian syndrome (PCOS).
Reference range values
ng/dL (SI: nmol/L = 0.0347 x ng/dL)
Male:
20Y-49Y 262-1593
>=50Y 181-758
Female:
Ovulating <20-80
Postmenopausal <20-62
Abnormal findings
In males, a low testosterone level can indicate :
- hypothalamic disease
- pituitary disease
- damage to the testes
Genetic diseases such as :
- Klinefelter's syndrom
- Kallman's syndrom
- Prader-Willi syndrom
- testicular failure and infertility
- acquired damage to the testes, such as alcoholism, physical injury, mumps
In males, a high testosterone level can indicate :
- testicular tumors
- adrenal tumors
- use of androgens
Increased testosterone in boys is usually the cause of early puberty.
In women, increased testosterone levels can indicate PCOS or an ovarian or adrenal gland tumor.