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Synthesis and Metabolism of Androgen in Male Reproductive
Organ
Prepared by:
V.Madhukar
Contents:
• Introduction
• Functions of Androgen
• Synthesis
• Metabolism
• Biochemical Functions
• Abnormalities related to testosterone
Androgen(steroid hormone)
• Androgen (from andro Greek prefix meaning masculine), also called androgenic hormone or testoid
• Androgens were first discovered in 1936. Androgens are also the original anabolic steroids and the precursor of all estrogens
• The primary and most well-known androgen is testosterone
Development
Maintenance
Male Sexual Characteristics
Introduction :
Functions of Androgen:
• Development of the male
i. Testes formation
ii. Early regulation
• Spermatogenesis
• Inhibition of fat deposition
• Muscle mass (Androgens promote the enlargement of skeletal muscle cells)
• Brain (Circulating levels of androgens can influence human behavior because some neurons are sensitive to steroid hormones)
Synthesis:The male sex hormones or androgens are produced by
Leydig cells of testes in response to LH and
To a minor extent by adrenal glands in both the sexes.
Ovaries also produce a small amount of androgens
Precursor: Cholesterol
It is first converted to pregnenolone by cytochrome p450 side chain cleavage enzyme which then forms androstenedione by two pathways:
1. Through progesterone (Progesterone (or ∆4) pathway)
2. Through 17-hydroxypregnenolone.(Dehydroepiandrosterone or ∆5 pathway)
Testosterone Synthesis in Leydig Cells
Metabolism:
SHBG: Sex Hormone Binding Globulin
DHT: Dihydrotestosterone
PSA: Prostate Specific Antigen
AR: Androgen Receptor
HSP: Heat Shock Protein
Group I hormone• Both testosterone and dihydrotestosterone
bind to a single class of receptors on the target tissues
• The affinity of DHT for the receptor is much higher compared to testosterone
• Receptor sites for androgens are found in muscle, brain, and other target tissues
Biochemical functions:Protein retention ( Anabolic action)
Effect on protein metabolism:
Androgens promote
RNA synthesis( transcription)
Protein synthesis( translation).
Rapid growth of musculo-skeletal system associated with puberty.
Effect on carbohydrate and fat metabolism-
Glycolysis,
Production of D-fructose from D-glucose by seminal vesicles.
fatty acid synthesis and
citric acid cycle.
Effects on mineral metabolism-
Androgens promote
Mineral deposition and bone growth
Kidney reabsorption of Na+, Cl- and water.
12
Abnormalities associated with male sex hormones:
Hypo-gonadism is a disorder characterized by a defect in testosterone synthesis. It may be of two types:
1. Primary hypogonadism is caused by a failure of testes to produce testosterone
2. Secondary hypogonadism is due to an impairment in the release of gonadotropins
References:
• Endocrinology & Metabolism, 4th Edition, Felig, Philip; Frohman, Lawrence A.
• Developmental Biology, Tenth Edition, Scott F. Gilbert