Testosterone is an androgen (male sex hormone) found in both men and women but in significantly larger quantities in men due to the testes. A small amount is made by our pituitary glands, and in women, by the ovaries. In pubescent boys, testosterone causes the voice to deepen, muscles to get bigger, sperm production to begin, and facial/ body hair to grow. Most of the testosterone in the blood is bound to a protein called sex hormone binding globulin. Testosterone that is not bound (“free” testosterone) may be checked if a man or a woman is having sexual problems, such as:

- Decreased sex drive

- Erectile dysfunction in men

- Infertility in men and women

- Delayed or accelerated puberty in boys

- Male features (deep voice, excessive hairiness) in women

In addition, certain conditions are known to affect free testosterone like hyperthyroidism and some types of kidney disease. 

Age-specific Reference Ranges (for men):

- 0-9 years < 1 pg/mL

- 10-11 years < 4 pg/mL

- 12-13 years < 68 pg/mL

- 14-15 years = 2-95 pg/mL

- 16-17 years = 26-119 pg/mL

- 18 years and older = 32-168 pg/mL

Tanner-stages spefific Reference Ranges (for men):

- Tanner stage I  < 3 pg/mL

- Tanner stage II < 15 pg/mL

- Tanner stage III < 68 pg/mL

- Tanner stage IV = 24-117 pg/mL

- Tanner stage V = 28-165 pg/mL

(To find out more about the different Tanner stages, please refer to: Tanner Stages)