Endocrinological Aspects of Pregnancy: Hormones, Functions, and Synthesis

 
Lecture – 03
Applied endocrinology of
pregnancy
 
Endocrinological structures during pregnancy
 
Carpus
 luteum
Placenta
 
Both structures act as temporary endocrine
organ.
P
erform 
steroidogenic activity
Steroidogenic activity of placenta is observed in
majority of mammals 
except DOG
 
2
 
Hormones of pregnancy
 
Mare
 and 
Ewe
 derives their progesterone
from 
placenta at later half of pregnancy
known as 
luteo-placental shift
 
Serum progesterone level 
remains
constant 
throughout pregnancy in cow
and ewe but in Sow, its 
high level is
observed during early stage of pregnancy
 
 
 
1.   Progesterone
Principal hormone for pregnancy
maintenance
During initial stage of pregnancy, functional
CL releases progesterone
CL persist throughout pregnancy in all species
except in mare
Cow, Doe and Sow – primary source of
progesterone is CL
 
 
3
 
R
ole of progesterone during pregnancy
 
It controls various essential functions during gestation period
 
Endometrial differentiation
Myometrial quiescence
Closure of the cervix
 Local immunotolerance in the pregnant uterus
 
4
 
2. Placental estrogens
 
Estradiol-17β is the most relevant form of estrogen found in dam blood
In 
sheep
 and 
cattle
 
Estrone
 and 
sulphonated form of estrogen 
remains high during
gestation period
Ruminanats and camelids, the maternal estrogen rises at uniform rate
Sudden peak of estrogen during mid gestation is physiological in Equines
Species specific placental estrogens in equines is termed as 
equilin and equilenin
 
5
 
Placental synthesis of estrogens
 
Bovine placenta synthesizes estrogen from cholesterol (precursor)
Equine placentae can not synthesize estrogen like bovine,  due to its dependency
on fetal gonads for  C
19
 precursor
Steroidogenesis associated with pregnancy in horse is a dependent process
involving placenta and fetus which led to the terminology -  
feto-placental unit
 
6
 
 Ruminants including the role of placental
estrogens
 
Preparation of the birth canal for
      parturition
 Myometrial excitability at advance stage
 Mammary gland development during late
      gestation
 
Functions of placental estrogens
 
Maternal estrogen levels start to increase
significantly between days 120-150
.
 
I
n ruminants 
sulphonated estrogen 
level
remains higher throughout pregnancy
exept immediate pre or intrapartal period
 
7
 
Androgens
 
C
19
 steroids
Androstenedione
 Dehydroepiandrosterone
(DHEA)
 Sulfonated DHEA (DHEAS)
 
C
19
 steroids act 
as
precursors for the
synthesis of bioactive
androgens
 
C
19
 steroids serves as
p
recursor for placental
estrogen synthesis in
equines
 
8
 
In rodents and ruminants these substances
named as
Placental lactogen (PL)
PRL-like proteins (PLPs)
 PRL-related proteins (PRPs)
Proliferin (PLF).
 
Pregnancy-associated prolactin and growth
hormones
 
Functions
In ruminants associated with
Development of uterus and mammary
gland
Transport of nutrients from the dam to
the fetal compartment
 
9
 
Relaxin/insulin-like family peptides
 
Commonly denoted by – RLNs
 
Source of RLNs
Placenta – Horse, cat, dog, rabbit and camel
 Carpus luteum – Pig and rodents
.
 
10
 
Function of RLNs are different in various
species
Decidualization
 Immunomodulation
 Quiescence of the myometrium
Maternal circulatory adaptations of
pregnancy
Stimulation of angiogenesis
 
RLNs functions
 
 uterine and vaginal growth
Development of the mammary gland
and/or nipples
During prepartal period
 Relaxation of the pubic ligament
 Preparation of the vaginal canal for
      parturition.
 
11
 
Endocrinology of pregnancy in mare
 
A different species to deal with
 
13
 
M
a
i
n
t
e
n
a
n
c
e
 
o
f
 
p
r
o
g
e
s
t
e
r
o
n
e
c
o
n
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e
n
t
r
a
t
i
o
n
 
d
u
r
i
n
g
 
p
r
e
g
n
a
n
c
y
 
Early stage of pregnancy, Primary corpus luteum
secrets progesterone followed by secondary carpora
lutea
 
Post day 150 matured placenta takes up secretion of
progesterone sufficient for physiological need of
pregnancy, phenomena is termed as 
luteo-placental
shift
 
Courtesy -  Kritika’s drawing
 
E
s
t
r
o
g
e
n
 
d
u
r
i
n
g
 
p
r
e
g
n
a
n
c
y
Plasma estrogen concentration remains low
during first trimester, gradually increases to peak
between 9
th
 to 11
th
 month, thereafter declines
near foaling
 
Endocrinology of pregnancy in mare
 
14
 
15
 
Thanks!
 
Any 
questions?
You can find me at:
alok9alright@gmail.com
 
D
r
 
A
l
o
k
 
K
u
m
a
r
A
s
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i
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P
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o
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c
u
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j
r
.
 
S
c
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V
e
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e
r
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a
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y
 
G
y
n
a
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c
o
l
o
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a
n
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O
b
s
t
e
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r
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s
B
i
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V
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C
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During pregnancy, endocrinological structures like the corpus luteum and placenta play vital roles in the production of hormones such as progesterone and estrogens. Progesterone maintains pregnancy by controlling essential functions like endometrial differentiation, myometrial quiescence, and local immunotolerance in the uterus. Placental estrogens, specifically estradiol-17, are important in various species, with unique synthesis processes observed, such as in bovines and equines. Understanding the roles and synthesis of these hormones is crucial for the successful progression of pregnancy.


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  1. Lecture 03 Applied endocrinology of pregnancy

  2. Endocrinological structures during pregnancy Carpus luteum Placenta Both structures act as temporary endocrine organ. Perform steroidogenic activity Steroidogenic activity of placenta is observed in majority of mammals except DOG 2

  3. Hormones of pregnancy 1. Progesterone Mare and Ewe derives their progesterone from placenta at later half of pregnancy Principal hormone for pregnancy known as luteo luteo- -placental shift placental shift maintenance During initial stage of pregnancy, functional CL releases progesterone Serum progesterone level remains constant throughout pregnancy in cow CL persist throughout pregnancy in all species and ewe but in Sow, its high level is except in mare observed during early stage of pregnancy Cow, Doe and Sow primary source of progesterone is CL 3

  4. Role of progesterone during pregnancy It controls various essential functions during gestation period Endometrial differentiation Myometrial quiescence Closure of the cervix Local immunotolerance in the pregnant uterus 4

  5. 2. Placental estrogens Estradiol-17 is the most relevant form of estrogen found in dam blood In sheep and cattle Estrone and sulphonated form of estrogen remains high during gestation period Ruminanats and camelids, the maternal estrogen rises at uniform rate Sudden peak of estrogen during mid gestation is physiological in Equines Species specific placental estrogens in equines is termed as equilin and equilenin 5

  6. Placental synthesis of estrogens Bovine placenta synthesizes estrogen from cholesterol (precursor) Equine placentae can not synthesize estrogen like bovine, due to its dependency on fetal gonads for C19precursor Steroidogenesis associated with pregnancy in horse is a dependent process involving placenta and fetus which led to the terminology - feto-placental unit 6

  7. Functions of placental estrogens Ruminants including the role of placental estrogens Preparation of the birth canal for Maternal estrogen levels start to increase significantly between days 120-150. parturition Myometrial excitability at advance stage Mammary gland development during late In ruminants sulphonated estrogen level remains higher throughout pregnancy exept immediate pre or intrapartal period gestation 7

  8. Androgens C19steroids Androstenedione Dehydroepiandrosterone (DHEA) Sulfonated DHEA (DHEAS) C19 precursors synthesis androgens steroids act as for the of bioactive C19steroids serves as precursor for placental estrogen synthesis in equines 8

  9. Pregnancy-associated prolactin and growth hormones In rodents and ruminants these substances named as Placental lactogen (PL) PRL-like proteins (PLPs) PRL-related proteins (PRPs) Proliferin (PLF). Functions In ruminants associated with Development of uterus and mammary gland Transport of nutrients from the dam to the fetal compartment 9

  10. Relaxin/insulin-like family peptides Commonly denoted by RLNs Source of RLNs Placenta Horse, cat, dog, rabbit and camel Carpus luteum Pig and rodents . 10

  11. RLNs functions uterine and vaginal growth Development of the mammary gland and/or nipples Function of RLNs are different in various species Decidualization Immunomodulation Quiescence of the myometrium Maternal circulatory adaptations of pregnancy Stimulation of angiogenesis During prepartal period Relaxation of the pubic ligament Preparation of the vaginal canal for parturition. 11

  12. Endocrinology of pregnancy in mare A different species to deal with

  13. Maintenance of progesterone concentration during pregnancy Early stage of pregnancy, Primary corpus luteum secrets progesterone followed by secondary carpora lutea Post day 150 matured placenta takes up secretion of progesterone sufficient for physiological need of pregnancy, phenomena is termed as luteo-placental shift Estrogen during pregnancy Plasma estrogen concentration remains low during first trimester, gradually increases to peak between 9thto 11thmonth, thereafter declines near foaling 13 Courtesy - Kritika s drawing

  14. Endocrinology of pregnancy in mare Hormones source Days of pregnancy Primary corpus luteum 01 - 35 Secondary carpora lutea 36 - 150 Progesteroe Placenta 151 till foaling Equine chorionic Gonadotropin Endometrial cups 36 - 140 Estrogen Placenta 100 - 330 14

  15. Thanks! Any questions? You can find me at: alok9alright@gmail.com Dr Alok Kumar Assistant Professor cum jr. Scientist Veterinary Gynaecology and Obstetrics Bihar Veterinary College, BASU. Patna 15

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