Andrology lecture 8 endocrinology of male

ENDOCRINOLOGY OF MALE
DOMESTCIC ANIMALS
Prof. Dr. G.N Purohit
MVSC, PhD, MNVAS
Dean Post Graduate Studies and University Head Dept. Veterinary
(Gynecology & Obstetrics)
College of veterinary & Animal Science, RAJUVAS
Bikaner, Raj., India.
Email: gnpobs@gmail.com
Dr. GN Purohit - Confidential - Content & Video Not Permitted for Commercial Purposes

About Me : Professor G N Purohit, MVSc, Ph.D, MNVAS
Head, Department of Veterinary
Gynecology and Obstetrics, Veterinary
College, Bikaner, Rajasthan, India

Todays Topic –Endocrinology of male reproduction
■ <Topic 1>Fetal development of testes and
associated structures.
■ <Topic 2>Endocrine regulation of testes function.
■ <Topic 3>Hormonal regulation of Spermatogenesis.
■ <Topic 4>Testosterone biosynthesis and function.

Primordial germ cells
Migrate
GONADS
Fetal development of Male Genitals
Differentiate into spermatogonia
Primitive
testes

Development of
medullary cords
occurs earlier in
males than in
females.

Sertoli cell Fetal Testes Leydig cell
Testosterone Insulin like factor 3
Wolffian duct Urogenital
swellings
Gubernaculum
Anti Mullerian
Hormone
Degeneration
of mullerian
ducts
Epididymis
Vas deferens
Seminal vesicles
Scrotum &
Penis
Testicular
descent
Urogenital
sinus
Prostrate
Bulbourethral
glands

At birth, the bull penis is short
and slender and lacks a
sigmoid flexure, and its apex is
fused to the inner lining of the
prepuce.
With puberty the penile and preputial
tissues separate, the penis elongates, and
a sigmoid flexure develops.
Testosterone
at puberty
Tissue separation proceeds irregularly
and in many bulls is completed only
after the onset of erectile activity.
Penile development in bulls

Endocrine
regulation of testes
function in adult
males

In adult bulls LH secretion occurs in
pulses (~30 min of secretion). LH
pulses in a bull, seem to occur
randomly 3 to 8 times a day.
Increased synthesis and
secretion of testosterone occur
within 30 min of LH pulses.
Pulsaltile discharge of FSH is much
less evident due to slower
clearance.
LH and FSH secretion is controlled
by testosterone:estradiol ratio and
inhibin secreted by Sertoli cells

Endocrine regulation of male animals

Prostaglandin F2
alpha increases
prolactin and LH
secretion in the
bull.

FSH acts on the seminiferous tubules of the testes and
is responsible for spermatogenesis i.e., from the initial
division of the spermatogonia through the formation of
secondary spermatocytes. Thereafter, testosterone is
responsible for sperm cell development.
LH stimulates the growth and development of interstitial
cells or Leydig cells in between the seminiferous tubules
of the testes and the secretion of the testosterone and
androgens from these cells.

FSH
Receptors
Sertoli Cells
Androgen
Binding Protein
LH
Leydig Cells
Testosterone (T)
5 alpha reductase
Aromatase
Dihydrotestosterone
Estrogen
Epididymis
T

High levels of testosterone, estrogen or
progesterone maintained by continuous
injections, feeding or steroid
producing tumors of the testes and adrenal
gland causes atrophy of the seminiferous
epithelium and interstitial cells. This process
can be reversed by withdrawal of the
exogenous source of steroids resulting
in testicular rebound phenomenon.

High levels of estrogens found in stallion
urine are mainly due to estrogen
produced by interstitial cells and or Sertoli
cells of the testes.
Sertoli cell tumor of canine testes is common
and they produce high levels of estrogens which
cause feminization and testicular atrophy in
males.
The inhibin secreted into the blood stream has a
negative feedback effect on FSH but not on LH
secretion.

ABP
• Androgen binding protein (ABP)
• ABP is produced by sertoli cells under the influence
of FSH and forms a complex with androgen.
• It is carried along with spermatozoa into
the epididymis.
Epididymis
•The epithelial cells of
the epididymis require high levels of
androgen for normal function- epididymal
transport, sperm maturation and storage.

TESTOSTERONE
Testosterone is a steroid hormone soluble in oil and alcohol but not in water.
Functions of Testosterone
Sexual differentiation of external male genitalia and descent of
the testes into scrotum
Keratinization of the preputial epithelium, separation of
glans penis from prepuce, growth of the penis and prepuce at puberty.
Growth and maintenance of accessory sex glands.
Sexual desire or libido, ability for normal erection and ejaculation.
Secondary sexual characteristics like hair or horn growth, male attitudes,
voice, increased bone thickness, increased muscle tissue with different
distribution of fat from female.
Maintenance of secretory and absorptive activities and structure of efferent
ducts, epididymis and ductus deferens including ampulla.
Spermiogenesis – development and maturation of spermatids and
spermatozoa.

Acetate
→
Cholesterol
→
Pregnenal
one →
Progesterone
→
Androst
enedio
ne →
Testos
terone
.
BIOSYNTHESIS OF TESTOSTERONE

Testosterone is the major
androgen produced by bull, dog
and human testes.
Androstenedione is the major
androgen from the
stallion’s testes.
Testosterone secreted from the
Leydig cells is carried in the
blood stream by an α –
globulin designated as steroid
binding globulin.
99% of the
circulatory testosterone is in bound
form and 1% free testosterone from
circulation enters the target cell.
In bull, testosterone is
sixteen times more potent
than androstenedione.

Re-cap – What we learned
■ The fetal testes develop early and the testosterone produced helps in development of ducts
scrotum and penis
■ The testicular development in male animals occurs in 3 periods infantile, pre-pubertal and pubertal
periods.
■ The testicular function in male animals is controlled by gonadotropins FSH and LH.
■ The FSH acts on Sertoli cells which helps in spermatogenesis up to secondary spermatocytes.
Thereafter testosterone helps in sperm development.
■ The LH hormone secreted in pulses acts on Leydig cells and helps in secretion of testosterone.
■ The testosterone diffuses into Sertoli cells and is converted to dihydrotestosterone and estradiol.
■ The testosterone: estradiol ratio and the inhibin secreted by Sertoli cells regulates the secretion of
FSH and LH.
■ Testosterone maintains the sex libido and also responsible for development of secondary sexual
characters.
■ Testosterone is the major androgen in bull, dog and humans whereas in stallions the major
androgen is androstenedione.

Contact me
Prof. Dr. G.N Purohit
MVSC, PhD, MNVAS
Head Dept. Veterinary (Gynecology & Obstetrics)
College of veterinary & Animal Science, Bikaner, Raj.India.
Email:gnpobs@gmail.com
Linked in : linkedin.com/in/dr-govind-narayan-purohit-13a04a17
YouTube Channel link : https://www.youtube.com/user
/gnpobs61/videos

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Andrology lecture 8 endocrinology of male

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