Estriol, Urine Creatinine Ratio Unit Converter

Estriol (E3) is the weakest of the three main estrogens in the body, alongside estradiol (E2) and estrone (E1). It is a short-acting estrogen that binds less strongly to estrogen receptors than its more potent counterparts.

This marker measures estriol in a urine sample, divided by urinary creatinine concentration to correct for urine dilution. The ratio approximates what a full 24-hour urine collection would show from a single convenient spot sample.

In non-pregnant individuals, estriol is produced in small quantities as a byproduct of estradiol and estrone metabolism in the liver. During pregnancy, levels rise dramatically because the placenta produces estriol in large amounts. As a urinary metabolite, estriol reflects activity through the 16-alpha-hydroxy estrogen metabolism pathway.

In non-pregnant individuals, estriol is produced mainly in the liver through 16-alpha-hydroxylation of estradiol and estrone by the enzyme CYP3A4. During pregnancy, the placenta produces estriol in large quantities using precursors from the fetal adrenal glands and liver.