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.

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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