Testosterone%20production%20n%20function.pptx

1. Testosterone
Prepared by:
Dr. Hazrat Bilal Malakandi, PT
DPT (IPMR, KMU), MSPT (KMU),
CHPE (KMU), CHR (KMU), PhD (KMU)
Demonostrator/Physical Therapist
IPMR, Khyber Medical University, Peshawar

2. Objectives of lecture
• Nature & Site of secretion of testosterone
• Mechanism of Production of testosterone
• Conversion & degradation of testosterone
• Functions of testosterone
• Regulation of testosterone

3. • Nature
–Steroid
• Sites of secretion
–In fetus
• By genital ridges under influence of male
chromosome Y (7th Week)
• Later by fetal testis under influence of HCGTH
from placenta
–Leydig cells
• After birth

4. Mechanism of Production
In adults
–Nervous stimuli  stimulate
hypothalamus which secrete
Luteinizing-hormone-releasing hormone
(LHRH)  stimulate ant. pituitary gland
 secrete LH & FSH  stimulate
Leydig cells  secrete testosterone

5. Cont …
In fetus
• Human chorionic gonadotropin from
placenta  causes Leydig cell formation
in testis  testosterone secreted.

6. Conversion in target cells
• Testosterone in target cells is converted
into
– Dihydrotestosterone (more active form)
– 5-alpha-abdrostanediol
• Some actions of testosterone depend
upon this conversion, while others do not.

7. Degradation and Excretion
• Testosterone that is not up taken by the
target cells is degraded by liver into
– Androsterone
– Dehydroepiandrosterone
• Conjugated as
– Glucoronides or
– Sulphates
• Conjugated products of degraded
testosterone are secreted in bile or in urine.

8. Functions of testosterone
1. In fetus
–Causes development of penis, scrotum,
prostate, seminal vesicle and male
genital duct
–Suppresses formation of female genital
organs in male fetus
–Causes decent of testis through inguinal
canal into the scrotum during last two
months of gestation.

9. Cont ….
2. Secondary sexual characters
–Characters of body which make their
appearance under influence of sex
hormones at puberty are called
secondary sexual characters
In male they include
• Baldness: testosterone causes decrease
hair growth on top of head, producing
baldness.

10. Cont ….
Body hairs:
• Testosterone causes increase hair growth
–Over pubis
–Upward along linea alba
–On chest, face and back
Voice:
• testosterone causes hypertrophy of
laryngeal mucosa and enlargement of
larynx which causes typical male bass

11. Cont ….
3. on testis
• Increase spermatogenesis
4. On protein metabolism
• Increase protein synthesis
5. On muscles
• Increase muscle development due to inc.
protein synthesis
6. On bones
• Increase bone thickness due to
– Increase total quantity of bone matrix

12. Cont ….
7. On male pelvis
• Narrow pelvis outlet & lengthen it
• Causes it funnel shaped
• Increase the strength of pelvis for load
bearing
8. Other functions
• Increase RBC count
• Increase Na and water reabsorption in distal
tubules of kidney

13. Regulation of Testosterone
• Negative feedback inhibition
–Excess testosterone secreted by leydig
cells  negative feedback inhibition of
LHRH secretion by hypothalamus 
inhibits LH secretion by ant pituitary
gland  inhibit testosterone by Leydig
cells