https://nabeelbeeran.blogspot.com/ Testosterone

1. Testosterone
Dr. Nabeel Beeran MBBS, MD
Department of Physiology
09/08/2019
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2. Specific Learning Objectives
At the end of the class you should be able to:
• What is semen analysis and understand the
importance of semen analysis
• Explain the source, normal plasma concentration and
physiological actions of testosterone
• Describe the regulation of testicular functions
• Explain cryptorchidism and castration
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4. Semen Analysis
• Volume: 2- 5 ml
• Milky apperance
• Alkaline pH: 7.5
• Specific gravity: 1.028
• Composition:
- Spermatozoa
- Epididymal secretion
- Secretions of seminal vesicles: fructose, fibrinogen,
prostaglandins, flavins, vit C.
- Secretion of prostate gland: spermine, citric acid,
cholesterol, clotting enzymes, fibrinolysin, zinc, acid
phosphatase, Prostate specific antigen (PSA)
- Secretion of bulbourethral gland: mucoid consistency
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5. Testosterone
• Source:
• DHT> Testosterone> Androsterone> DHEA
• Normal plasma concentration:
• Males: 300-1000ng/dL
• Females: 30-70ng/dL
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6. Physiological actions of testosterone:
A) Foetal life:
• Effect on genital and Psychological differentiation
• Effect on descent on testis:
B) Puberty:
• Effect on external genitalia
• Effect on accessory sex organs
• Development of male secondary sexual characters.
• Spermatogenesis
• Psychological behaviour and Libido
• Anabolic and growth promoting effects
- Protein synthesis –muscle
- Bone growth
- Basal metabolic rate
- Water and electrolyte balance 6

7. C) In adults:
• Hair growth
• Psyche
• Bone
• Spermatogenesis
• Hematopoiesis
• Regulation of gonadotropin secretion
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8. Regulation of testicular functions
Regulation of spermatogenesis
1. Stimulatory control
• Role of hypothalamus
• Role of anterior pituitary
• Role of FSH & LH
• Role of growth hormone
• Role of testicular hormone
2. Feedback inhibitory control
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9. Control of testosterone secretion:
In fetus: During fetal life, HCG secreted by placenta
stimulates the development of Leydig cells in the
testes of fetus and causes testosterone secretion.
In adults:
1. Stimulatory control
• Role of hypothalamus
• Role of anterior pituitary
• Role of LH
2. Feedback inhibitory control
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10. Applied Aspects
1. Cryptorchidism
2. Extirpation (Castration)
3. Hypogonadism in males
4. Hypergonadism in males
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11. Cryptorchidism
• Refers to a condition in which the descent of
testes may fail to occur or may be
incomplete.
• Undescended testes may lie in the lumbar
region, in the iliac fossa, in the inguinal canal,
or in the upper part of scrotum.
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12. • Treatment : -Surgical correction.
-Administration of testosterone
or gonadotrophic hormone can cause the
testis to descend provided the inguinal canal is
large enough to allow passage of testis.
• Complication: Spermatogenesis often fails to
occur in cryptorchidism (due to high
temperature of the abdominal cavity)
resulting in sterility.
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13. Extirpation/ castration:
Effects of castration before puberty:
• Permanent sterility.
• Underdevelopment of external genitalia and
accessory sex organs.
• Underdevelopment of secondary sexual characters.
• Abnormal bone growth.
Effects of castration after puberty:
• Accessory sex organs – atrophy.
• Sexual desire and activity is slightly diminished.
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14. Summary
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15. References
• Guyton and Hall Textbook of Medical Physiology ,
• GK Pal Comprehensive textbook of Medical
Physiology. Volume 1
• Textbook of Medical Physiology (2nd edition)- Indu
Khurana
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16. Thank
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