of the steroids in the different zones. Whether such distribution of labour exists in
production of different steroids in the adrenocortical cells of non-mammalian vertebrates is unknown.
a) Biogenesis of the Corticosteroids. Adrenocortical hormones are formed principally as the result of a series of hydroxylations to the steroid nucleus of cholesterol.
It is considered possible that some steroid hormones are formed without the mediation of cholesterol, but the details of this are unknown. The adrenal cortex, using
21
Acetic Acid
H
0
H-C-C-?
- -
H 'OH
Pregnelolone
20. 22 - desmolase
Mevalonic -
Squalene - -
Acid
22 - hydrox ylase
20a 22~ Dihydroxy , ~~---'----Cholesterol
7
Cholesterol
1 20« - hydroxylase
20a - Cholesterol
I
I
I
I
? :
I
t
3 p-hydroxysteroid
dehydrogenase
isomerase
?
--.,
I
I
I
I
I
I
I
I
I
I
t
f
IOestrogens I
CH 3
I
CO
,m IProgesterone I
17a-hYdr~ O~\
~
21 hydroxylase
"
17a -Hydroxyprogesterone
21- hydroxylase 1
II-Deoxycorticosterone
17 a-Hydoxy/
-11 Deoxycorticosterone
r::
11p.hydrOXYlaS!CH OH
C
1
H 20H
0 C
1
H 20H
II 2
18 hydroxylase
II CO
- - - - - -
CO
CO
+
H C
I corticosterOidDsD' HO
--OH
& 0
__1_8h_
Y..:.dro_X-,y=-ste_ro_i_d_-.
aso o -
"
dehydrogen ase
_
o h
0
h
0
h
IAndrogens'
Cortisol
Corticosterone
Aldosterone
~ - hydroxylase
1a - Hydoxycorticosterone
Fig. 2.8 Some of the steps in the biogenesis of corticosteroids and their relationship to the
formation of other steroid hormones.
73