Testosterone is one of the major hormones that induces male secondary sexual characteristics such as deepening voice and growth of body hair. Typically, boys don't start making detectable amounts of testosterone until puberty. For this reason, before age 10, testosterone levels range from barely detectable to only 20 ng per dL of blood, which is only about 10 percent of the levels that are detectable after puberty.
Proper sexual development of boys into men requires the production and activity of testosterone. As described by the KidsHealth.org article on testosterone, this hormone is made in testes of men, and is responsible for inducing many of the changes that are typically associated with puberty. Testosterone production begins once the boy's brain begins to release two hormones from the pituitary gland that subsequently stimulate the testes.
Immediately after birth, an infant boy may have slightly elevated levels of testosterone, according to the Mayo Clinic description of testosterone levels in boys. In as few as six months, however, this level will drop to a range of undetectable to 20 ng per dL of blood. Total testosterone remains at this low level until a boy reaches puberty around ages 10 to 13. At this point, testosterone levels can rise to high levels near 1,000 ng per dL.
High Testosterone Levels
When adolescent boys display seemingly inappropriately fast development of sexual characteristics, a physician may order a testosterone test. According to Lab Tests Online, reasons for this test revealing high testosterone levels can vary. Some common causes are tumors or congenital adrenal hyperplasia. Each of these causes of increased rate of sexual development can be serious and typically require medical attention.
Low Testosterone Levels
Alternatively, boys who do not seem to be developing secondary sexual characteristics late into their teenage years may require a testosterone test to determine whether lack of testosterone production is the cause. According to the Merck article on delayed puberty, small courses of testosterone may actually stimulate development if low levels are at the root of the problem. While there are many causes of delayed puberty, often treatment of the underlying cause, coupled with hormone replacement, may be beneficial.
All boys develop at different rates, and therefore it is often difficult to determine exactly when a testosterone test is abnormal. Puberty onset can vary by a number of years, according to the KidsHealth.org article, and therefore testosterone may not be detectable for long periods of time. If you feel that your child is not developing at a proper rate, it is important to discuss with his physician possible causes and strategies for determining whether intervention is necessary.