Testosterone is produced in the testes and is responsible for male sexual development and function. It regulates spermatogenesis, muscle growth, bone growth, and other physiological processes. Levels are controlled by the hypothalamus and pituitary gland through LH secretion. Semen analysis evaluates semen volume, pH, viscosity, and the presence of secretions from testes, seminal vesicles, prostate, and bulbourethral glands. Cryptorchidism is the failure of one or both testes to descend into the scrotum, which can impair fertility if not surgically corrected. Castration before puberty prevents sexual maturation and function, while after puberty secondary sex characteristics remain but sexual desire and function

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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