The Hair Loss Encyclopedia
relative length of index to ring finger
The 2D:4D ratio, also known as the digit ratio, refers to the comparative length of the second digit (index finger) to the fourth digit (ring finger). This ratio is often used as a biomarker for prenatal hormone exposure, with a lower ratio (shorter index finger relative to the ring finger) typically indicating higher exposure to testosterone, and a higher ratio indicating higher exposure to estrogen. This measure has been linked to various biological and behavioral traits, including susceptibility to certain diseases and conditions.