TESTOSTERONE

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Testosterone

1. Testosterone Dr. Nabeel Beeran MBBS, MD Department of Physiology 09/08/2019 1

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 2

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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 4

5. Testosterone Source: DHT> Testosterone> Androsterone> DHEA Normal plasma concentration: Males: 300-1000ng/dL Females: 30-70ng/dL 5

6. Physiological actions of testosterone: Foetal life: Effect on genital and Psychological differentiation Effect on descent on testis: 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. In adults: Hair growth Psyche Bone Spermatogenesis Hematopoiesis Regulation of gonadotropin secretion 7

8. Regulation of testicular functions Regulation of spermatogenesis 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 8

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: Stimulatory control Role of hypothalamus Role of anterior pituitary Role of LH 2. Feedback inhibitory control 9

10. Applied Aspects Cryptorchidism Extirpation (Castration) Hypogonadism in males Hypergonadism in males 10

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. 11

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. 12

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. 13

14. Summary 14

15. References Guyton and Hall Textbook of Medical Physiology , GK Pal Comprehensive textbook of Medical Physiology. Volume 1 Textbook of Medical Physiology (2 nd edition)- Indu Khurana 15

16. Thank you 16