2. Steroid hormones
Synthesized in mammals by the ovary, testis, A.cortex corpus luteum
and placenta
The activity of sex hormones controlled by the adenohypophyseal
hormones.
Bcos of this, the sex hormones are, some times referred to as 20
sex
hormones of the adenohypophysis.
3 types are sex hormones are recognized.
1. the estrogens (female / ovarian / follicular hormones)
2. the androgens ( male / testicular hormones)
3. the gestogens ( corpus luteal hormones)
3. The sex hormones are concerned with sexual processes
and the development of 20
characteristics which
differentiate males from females
The adrenal cortical hormones perform a variety of
important functions related to cell metabolism.
Based on the no.of C atoms present in the molecule, the
steroid hormones may be named as C18,C19 or C21 steroids.
4. Structure:-
Mammalian ovary contains ovarian follicles and corpus
lutea.
Hormones produced mainly in the follicles are known as
estrogens.
Estrogens are derivatives of C18 hydro carbon, estrane.
The imp estrogens are
1. β-estradiol ( C18H24O2)
2. Estriol (C18H24O3)
3. Estrone (C18H22O2)
5. Estrone is the 1st
known member of the sex hormones.
Isolated from the urine of pregnants.
All these are characterized by the absence of a CH3 group at C10 and
by the aromatic ring A, making the OH group phenolic in character.
Β-estradiol is the most potent estrogens.
Estrone is less potent and estriol is least active.
Their relative potencies are 50:5:1.
Although ovary is the chief source of estrogens, they are in smaller
amts also produced by the testis& A.cortex.
6. Estrogen production is highest when a woman is young & slows down
with age.↑
Biosynthesis:-
In non-pregnant females, estrogen is mainly synthesized in the ovary.
The estrogen(as well as androgen) transported by binding to a
specific plasma protein called sex steroid binding protein.
The amt of SBT increases in pregnancy or estrogen therapy which
results in reduced androgenic action.
Testosterone, an androgen is the precursor of estrogens.
7. Most of the metabolic reactions of the estrogens take place in the
liver
Estradial - 17β 2-OH-estradiol-17β 2-
methoxyestradiol-17β 2-methoxyestrone
Estrone 16→ α
-hydroxyestrone
↓ ↓
2-OHestrone Estriol
Estriol is the principal estrogen found in the placenta and urine of
pregnants.
It is produced by hydroxylation of estrone at C16 and reduction of keto
group at C17
8. Acetate cholesterol pregnenolon
progesteron testosterone estrogen
Regulation of Secretion of Estrogen:-
The secretion of estrogen is regulated by
FSH released from anterior pituitary.
The release of FSH is caused by the
gonadotropic releasing hormone secreted
from hypothalamus.
9. Effects on uterus
Effects on fallopian tubes
Effects on vagina
Effect on the breast
Effects on 20
sexual characteristics
Effects on bones
Effects on protein & fat metabolism
Effects on electrolyte balance
