USMLE Step 2 CK Lecture Notes 2019: Obstetrics/Gynecology (Kaplan Test Prep)

ESTROGEN

Estrogens are steroid hormones that occur in 3 forms. Each form has unique
significance during a woman’s life.

Table I-1-1. Estrogens  Throughout  a   Woman’s Life

Estradiol Nonpregnant   reproductive    years Follicle

Granulosa

Estriol Pregnancy Placenta

from    fetal   adrenal DHEAS

Estrone After   menopause Adipose

from    adrenal steroids

Estradiol   is  the predominant moiety  during  the nonpregnant reproductive

years.  It  is  converted   from    androgens   (produced   from    cholesterol in  the

follicular  theca   cells), which   diffuse into    the follicular  granulosa   cells

containing  the aromatase   enzyme  that    completes   the transformation  into

estradiol.

Estriol is  the main    estrogen    during  pregnancy.  Dehydroepiandrosterone-

sulfate (DHEAS) from    the fetal   adrenal gland   is  the precursor   for 90% of

estriol converted   by  sulfatase   enzyme  in  the placenta.

Estrone is  the main    form    during menopause.   Postmenopausally,   adrenal

androstenedione is  converted   in  peripheral  adipose tissue  to  estrone.