Explore the intricate world of sex hormones with our comprehensive online guide! From the fundamental principles of hormone synthesis to the dynamic processes of the menstrual cycle and spermatogenesis, this resource offers a deep dive into the fascinating realm of reproductive biology. Discover ho...
Sex Hormones
Sex hormones are produced by the gonads, under control of pituitary gonadotropins (FSH and LH),
and by the adrenal cortex (zona reticularis), that is their main source before puberty (for female still plays
a role for secondary sexual characteristics, but still a minor role).
GnRH, LH and FSH have circadian fluctuations, 4 peaks/day on a generally low baseline.
Sex hormones are steroid hormones that contain
the cyclopentane-perhydrophenanthrene
(three 6-carbon and one 5-carbon rings) steroid
group, which is present also in cholesterol.
This steroid group is made of 17 carbons; cholesterol
has 27 carbons (8 in a lateral chain on the
pentagon + 2).
6 carbons of the lateral chain are cleaved by
desmolase (CYP11A1) producing
pregnenolone and other 21-C molecules
(pregnane derivatives), among which
progesterone is a female sex hormone, while
corticosterone and cortisol are glucocorticoids.
Cleavage of the remaining 2 carbons of the lateral
chain leaves 19-C compounds, with two carbons still
attached to the hexagonal rings, which are
androstane derivatives, among which androgens.
The cleavage of the carbon attached to the first ring
(by the aromatase enzyme) makes the latter aromatic
and produces estrone and estradiol, the main
estrogens and other estrane derivatives. (18C)
Apart from the limited basal amount of sex
hormones produced by the adrenal cortex:
• Progesterone is mainly produced by the
corpus luteus in the ovary during the
second half of the menstrual cycle.
• Androgens (testosterone) are mostly
produced by the gonads, in particular by
theca cells (that surround the follicle) in the
ovaries and by Leydig cells in the testis.
• Estrogens are produced by granulosa
cells during the maturation of the follicle, using the testosterone produced by theca cells, which
is not therefore distributed to a significant extent to other tissues.
29 Body At Work II
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