Testosterone

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Testosterone
2D structure for Testosterone
Chemical Name	17-hydroxy-10,13-dimethyl-1,2,6,7,8,9,11,12,14,15,16,17-dodecahydrocyclopenta[a]phenanthren-3-one
Chemical Formula	C₁₉H₂₈O₂
CAS Number	58-22-0
Chemical Information	HMDB00234
Biochemical Taxonomy	Steroids and Steroid Derivatives
Functional Taxonomy	Not Available
Nutritional Taxonomy	Not Available
Metabolic Pathways	Androgen and Estrogen Metabolism Bile Acid Biosynthesis C21-Steroid Hormone Metabolism Pentose and Glucuronate Interconversions Porphyrin and Chlorophyll Metabolism Starch and Sucrose Metabolism
Biofluid Location	Blood Cerebrospinal Fluid (CSF) Saliva Urine
Tissue Location	Gonads Hypothalamus Muscle Sperm Testis Brain
Normal Biofluid Concentrations	Blood: 0.000016 (0.000003-0.00003) uM Blood: 0.00043 (0.00017-0.0007) uM Cerebrospinal Fluid (CSF): 0.0007 (0.0005-0.0008) uM Cerebrospinal Fluid (CSF): 0.00101 (0.00002-0.002) uM Saliva: 0.000677 (0.000590-0.000764) uM Saliva: 0.00120 (0.00108-0.00133) uM Urine: 0.000121 +/- 0.00002149 umol/mmol creatinine Urine: 1.07 +/- 0.19 umol/mmol creatinine
Normal Tissue Concentrations	Not Available
Diseases / Conditions Related to Nutrition	Hypogonadism Male prepuberty Male workers occupationally exposed to cadmium
Other (Monogenic Disorders)	Not Available
Abnormal Biofluid Concentrations	Blood (Hypogonadism): 0.010 +/- 0.013 umol/L Blood (Male prepuberty): 0.0003 (0.00010-0.00050) uM Blood (Male workers occupationally exposed to cadmium): 9.31 (3.31-19.95) uM
Abnormal Tissue Concentrations	Not Available
Physiological Processes	Not Available

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Introduction

guidelines
testosterone is the most important androgen in potency and quantity. testosterone is synthesized and released by the Leydig cells that lie between the tubules and comprise less than 5% of the total testicular volume. testosterone diffuses into the seminiferous tubules where it is essential for maintaining spermatogenesis. Some binds to an androgen-binding protein (ABP) that is produced by the Sertoli cells and is homologous to the sex-hormone binding globulin that transports testosterone in the general circulation. The ABP carries testosterone in the testicular fluid where it maintains the activity of the accessory sex glands and may also help to retain testosterone within the tubule and bind excess free hormone. Some testosterone is converted to estradiol by Sertoli cell-derived aromatase enzyme. Leydig cell steroidogenesis is controlled primarily by luteinizing hormone with negative feedback of testosterone on the hypothalamic-pituitary axis. The requirement of spermatogenesis for high local concentrations of testosterone means that loss of androgen production is likely to be accompanied by loss of spermatogenesis. Indeed, if testicular androgen production is inhibited by the administration of exogenous androgens then spermatogenesis ceases. This is the basis of using exogenous testosterone as a male contraceptive. testosterone is converted to dihydrotestosterone by 5a-reductase type 2 (EC 1.3.1.22, SRD5A2), the androgen with the highest affinity for the androgen receptor. SRD5A2 deficiency illustrates the importance of dihydrotestosterone for external virilization, as individuals with this condition have normal male internal structures but their external genitalia are of female appearance. There is now clear evidence that the human fetal testis and also the fetal adrenal gland is capable of testosterone biosynthesis during the first trimester. Regardless of the source of androgen production, the target tissue responds by male sexual differentiation of the external genitalia by the end of the first trimester. It is clear that testicular damage may result in loss of testosterone production or the loss of spermatogenesis or both. Loss of androgen production results in hypogonadism, the symptoms of which reflect the functions of testosterone. Male hypogonadism is defined as failure of the testes to produce normal amounts of testosterone, combined with signs and symptoms of androgen deficiency. Systemic testosterone levels fall by about 1% each year in men. Therefore, with increasing longevity and the aging of the population, the number of older men with testosterone deficiency will increase substantially over the next several decades. Serum testosterone levels decrease progressively in aging men, but the rate and magnitude of decrease vary considerably. Approximately 1% of healthy young men have total serum testosterone levels below normal; in contrast, approximately 20% of healthy men over age 60 years have serum testosterone levels below normal. (PMID: 17904450, 17875487)