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3 Sex Hormones
3 Sex Hormones
3 Sex Hormones
3 Sex Hormones
3 Sex Hormones
3 Sex Hormones
3 Sex Hormones
3 Sex Hormones
3 Sex Hormones
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3 Sex Hormones

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Part 3 of "Science & Sexuality." Sex hormones, how they're made and how they work.

Part 3 of "Science & Sexuality." Sex hormones, how they're made and how they work.

Published in: Health & Medicine, Technology
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  • 1. Hormones That Alter Default Sexual Condition
    • Testosterone
    • Dihydrotestosterone
    • Estrogens
  • 2. 3 Pathways of Steroid Hormone Action Estrogen Brain organization Aromatase Adapted from Ganong, William F. REVIEW OF MEDICAL PHYSIOLOGY 22 nd ed. Lange Medical Books/McGraw-Hill (2005)
  • 3. Synthesis of Androgens & Estrogens Ganong, William F. REVIEW OF MEDICAL PHYSIOLOGY 22 nd ed. Lange Medical Books/McGraw-Hill (2005)
  • 4. 5  -Reductase Enzyme Converts Testosterone to Dihydrotestosterone Ganong, William F. REVIEW OF MEDICAL PHYSIOLOGY 22 nd ed. Lange Medical Books/McGraw-Hill (2005)
  • 5. Aromatase Enzyme Converts Androgens to Estrogens Ganong, William F. REVIEW OF MEDICAL PHYSIOLOGY 22 nd ed. Lange Medical Books/McGraw-Hill (2005)
  • 6. Aromatase mRNA in Adult Rhesus Monkey Brain
    • High in the bed nucleus of the stria terminalis > medial preoptic/anterior hypothalamus > amygdala
    • Intermediate in the medial basal hypothalamus (infundibular nucleus, median eminence, ventromedial nucleus) > lateral preoptic/anterior hypothalamus
    • Low in the septum > lateral-dorsal-medial hypothalamus
    • Undetectable in cingulate and parietal cortex, hippocampus, and cerebellum
    • Similar results in rat
    • Control of aromatase enzyme synthesis is at transcription level (mRNA correlates with aromatase activity; in rat, quail, and now monkey)
    • Abdelgadir, S.E., Roselli, C.E., Choate, J.V. and Resko, J.A. Distribution Of Aromatase Cytochrome P450 Messenger Ribonucleic Acid In Adult Rhesus Monkey Brains. BIOLOGY OF REPRODUCTION, 57: 772-777 (1997)
  • 7. Testosterone Causes Its Own Conversion to Estrogen
    • T & DHT induce aromatase activity in brain
      • T regulates brain aromatase activity in rat & quail
      • Both T and DHT treatments increased aromatase mRNA in the preoptic area and MBH of the male rat
    • Estrogen then mediates hormonal effects in certain hypothalamic areas
    • Testosterone would need to bind with its receptor and cause transcription of aromatase mRNA
    • In contrast, estrogen treatment induces aromatase activity in the preoptic area without affecting mRNA level
  • 8. Aromatase Enzyme
    • Converts androstenedione and testosterone to estrone (E1) and estradiol (E2), respectively
    • Encoded by CYP19 gene
      • Expressed at high level; aromatase catalyzes both conversions producing estrone & estradiol
        • Placenta
        • granulosa cells of ovarian follicles (expression depends on cyclical gonadotropin stimulation)
      • Expressed at low level; aromatase c onverts androstenedione to estrone in “peripheral tissues”
        • Subcutaneous fat
        • Liver
        • Muscle
        • Brain
        • Breast
    • Premenopausal women: estrogen production primarily from the ovaries
    • Postmenopausal women: estrogen production primarily from peripheral tissues
  • 9. Aromatization in Hypothalamus May Permanently Alter the Brain
    • Aromatization in hypothalamus may be responsible for imprinting the brain and inhibiting development of cyclicity in rats
    • Neonatal androgen secretion therefore serves to masculinize the male rodent with subsequent development of male behavioral and neuroendocrinological patterns
      • Aromatization of testosterone is greater in hypothalamus than cortex
      • Hypothalamus of males have higher conversion than females while testicular feminized mice resemble females (Shows testosterone is needed for aromatase activity)
    • Rosenfeld, J.M., Daley, J.D., Ohno, S., and YoungLai, E.V. Central Aromatization Of Testosterone In Testicular Feminized Mice. EXPERIENTIA, 33/10: 1392 (1977)

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