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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.

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  • 1. Hormones That Alter Default Sexual Condition <ul><li>Testosterone </li></ul><ul><li>Dihydrotestosterone </li></ul><ul><li>Estrogens </li></ul>
  • 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 <ul><li>High in the bed nucleus of the stria terminalis > medial preoptic/anterior hypothalamus > amygdala </li></ul><ul><li>Intermediate in the medial basal hypothalamus (infundibular nucleus, median eminence, ventromedial nucleus) > lateral preoptic/anterior hypothalamus </li></ul><ul><li>Low in the septum > lateral-dorsal-medial hypothalamus </li></ul><ul><li>Undetectable in cingulate and parietal cortex, hippocampus, and cerebellum </li></ul><ul><li>Similar results in rat </li></ul><ul><li>Control of aromatase enzyme synthesis is at transcription level (mRNA correlates with aromatase activity; in rat, quail, and now monkey) </li></ul><ul><li>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) </li></ul>
  • 7. Testosterone Causes Its Own Conversion to Estrogen <ul><li>T & DHT induce aromatase activity in brain </li></ul><ul><ul><li>T regulates brain aromatase activity in rat & quail </li></ul></ul><ul><ul><li>Both T and DHT treatments increased aromatase mRNA in the preoptic area and MBH of the male rat </li></ul></ul><ul><li>Estrogen then mediates hormonal effects in certain hypothalamic areas </li></ul><ul><li>Testosterone would need to bind with its receptor and cause transcription of aromatase mRNA </li></ul><ul><li>In contrast, estrogen treatment induces aromatase activity in the preoptic area without affecting mRNA level </li></ul>
  • 8. Aromatase Enzyme <ul><li>Converts androstenedione and testosterone to estrone (E1) and estradiol (E2), respectively </li></ul><ul><li>Encoded by CYP19 gene </li></ul><ul><ul><li>Expressed at high level; aromatase catalyzes both conversions producing estrone & estradiol </li></ul></ul><ul><ul><ul><li>Placenta </li></ul></ul></ul><ul><ul><ul><li>granulosa cells of ovarian follicles (expression depends on cyclical gonadotropin stimulation) </li></ul></ul></ul><ul><ul><li>Expressed at low level; aromatase c onverts androstenedione to estrone in “peripheral tissues” </li></ul></ul><ul><ul><ul><li>Subcutaneous fat </li></ul></ul></ul><ul><ul><ul><li>Liver </li></ul></ul></ul><ul><ul><ul><li>Muscle </li></ul></ul></ul><ul><ul><ul><li>Brain </li></ul></ul></ul><ul><ul><ul><li>Breast </li></ul></ul></ul><ul><li>Premenopausal women: estrogen production primarily from the ovaries </li></ul><ul><li>Postmenopausal women: estrogen production primarily from peripheral tissues </li></ul>
  • 9. Aromatization in Hypothalamus May Permanently Alter the Brain <ul><li>Aromatization in hypothalamus may be responsible for imprinting the brain and inhibiting development of cyclicity in rats </li></ul><ul><li>Neonatal androgen secretion therefore serves to masculinize the male rodent with subsequent development of male behavioral and neuroendocrinological patterns </li></ul><ul><ul><li>Aromatization of testosterone is greater in hypothalamus than cortex </li></ul></ul><ul><ul><li>Hypothalamus of males have higher conversion than females while testicular feminized mice resemble females (Shows testosterone is needed for aromatase activity) </li></ul></ul><ul><li>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) </li></ul>

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