Estrone (E1)
What it measures, and what changes the number.
Estrone is a weaker estrogen than estradiol. Much of it is made outside the ovaries, particularly in fat tissue, by conversion of androstenedione, and it becomes the predominant estrogen after menopause. The test measures estrone in serum.
It is usually read alongside estradiol, since the two convert into each other, and with androstenedione, its main precursor. FSH, LH and SHBG are often included when the wider hormonal picture is being assessed.
Method has a large effect on the result. Mass spectrometry is generally preferred because some immunoassays cross-react with related compounds such as estrone sulfate, which circulates in much higher amounts. Results from different labs or methods may therefore differ. Labs may print it as Estrona.
Often read alongside: Estradiol (E2), Androstenedione, FSH, LH, SHBG