The receptor/hormone complex * then binds with a specific receptor * stimulating the affected gene to transcribe mRNA.* The newly transcribed mRNA moves to ribosomes in the cytoplasm where it directs the translation (synthesis) of specific proteins. * Steroid hormones such as * Aldosterone, * Cortisol, * Testosterone, * Estrogen, * Progesterone and * Thyroxine are examples of direct gene activation hormones. *
MALE REPRODUCTIVE SYSTEM II
Dr. Nilesh Kate
DR NILESH N KATE
ESIC MEDICAL COLLEGE
Depends On Testosterone
Testicular Leydig Cells Secrete Testosterone
Sertoli Cells Secrets Inhibin, Oestrogen, And
Testes Descend And Pass Out Of Abdominal
Leydig cells -- interstitial connective tissue
between seminiferous tubules.
Numerous in Newborn and after puberty
Decreases after 40 and absent in old age i.e.
around 80 years of age.
Normal secretion 4-9 mg /day
Plasma testosterone 0.65 microgram %
TRANSPORT IN PLASMA
2 % in free form
98 % in bound to plasma proteins form
68 % --- albumin.
30% --- testosterone binding globulin i.e. sex
steroid binding globulin . (SSBG)
Steroid precursor for blood Oestrogen
■ Testosterone converted into
Dihydro testosterone by 5 ά reductase.
■ Has more than twice biological activity.
FORMATRION OF ANDROGEN
FUNCTIONS OF TESTOSTERONE
TESTOSTERONE: BEFORE BIRTH
Effect on sex differentation in fetus
Gonadal sex differentation
Y chromosomes – TDF
Effect on descent of testes
from abdomen to testis
TDF NO TDF
TESTOSTERONE NO TESTOMIS
Degenerates MULLERIAN (Parameso) uterus and tubes
epididymis, vas def.&
ejaculatory ducts form WOLFFIAN (Meso) degenerates
PUBERTY IN THE MALE
Usually 10-14 years old
Endocrine, physical, and behavioral growth.
Leydig cells “awake”
TESTOSTERONE: AT PUBERTY
■ EFFECTS ON EXTERNAL GENITALIA
TESTOSTERONE – Enlargement of penis
DHT – Scrotum size , pigmentation, Rugal folds
■ EFFECT ON ACCESSORY SEX ORGANS
TESTOSTERONE -- SEMINAL VESICLES
DHT -- PROSTATE SIZE AND SECREATIONS
■ MALE SECONDARY SEX CHARACTER
Body hair – male pattern, beard growth
Voice – Due To Larynx Enlargement, Low Pitch
Muscle mass and shoulder girdle
Changes in skin – thicker & darker.
EFFECT ON PSYCHE
Libido – initiate sexual drive
ANABOLIC AND GENERAL GROWTH
Nitrogen retention - misuse
Bone growth – Somatomedins C level
Basal metabolic rate
Water electrolyte balance
TESTOSTERONE: IN ADULTS
Hair Growth – Male baldness.
Psyche – behavioral attitude
Bone – prevent bone loss & osteoporosis.
Circulating and stored body fats :-
Gonadotrophins secretion Suppression of
Direct Gene Activation
MODE OF ACTION OF ANDROGENS
CONTROL OF LH AND FSH SECRETION
Testosterone inhibits LH
and GnRH production.
constant secretion of LH
Declines gradually in
men over 50 years of
to DHT, which inhibits
Inhibin inhibits FSH
producing estradiol in the
brain, is required for the
negative feedback effects.
Insert fig. 20.13
ENDOCRINE FUNCTION OF THE TESTES
■ Testosterone and its
responsible for initiation
and maintenance of body
changes in puberty.
■ Stimulate growth of
muscles, larynx, and bone
growth until sealing of the
Act in paracrine fashion,
Insert fig. 20.15
Hormonal Control of Spermatogenesis
Formation of primary spermatocytes and entry
into early prophase I, begin during embryonic
Spermatogenesis arrested until
Testosterone required for completion of meiosis
and spermatid maturation.
Secrete paracrine regulators:
Transforming growth factor.
FSH necessary in the later stages of spermatid
Sertoli and Leydig cells secrete small
amounts of estradiol.
Receptors found in Sertoli and Leydig cells and
May be responsible for:
Negative feedback in brain.
Sealing of epiphyseal plates.
Regulatory function in fertility.
Hopogonadism in males
Hopergonadism in males
(Gk. kryptos – hidden + orchis - testis)
■ In 97% of male newborns, testes are
present in the scrotum before birth.
■ In most of the remainder, descent will
be completed during the first 3 months
■ However, in less than 1% of infants,
one or both testes fail to descend.
The condition is called
Cryptorchidism and may be
caused by decreased androgen
The undescended testes fail to
produce mature spermatozoa
and the condition is associated
with a 3% to 5% incidence of
Removal of testes.
Before puberty --- ENUCHOIDISM
Underdevelopment of external
Underdevelopment of secondary
Abnormal bone growth.
Absent or deficient testicular hormone.
Due to –
congenital non functioning of testes.
Extirpation of testes.
Absent androgen receptors
■ Frohlich’s syndrome
Obesity along with Enuchoidism
Excessive secretion in tumors of
Precocious pseudo puberty
Rapid growth of muscles
Sex organs and secondary
sex characters at early age.
Also secretes Oestrogen so
Inability of sperm to fertilize ovum
-- Androgen dysfunction with normal sperm
-- Isolated dysfunction of sperm cell
-- Combined androgen and sperm cell
-- Failure of deposition of sperm in female
Permanent method for sterilization in males
cut and ligated