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Steroid Hormone Pathway

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Steroid Hormone Pathway, Sex Hormone Synthesis, Cortisol Synthesis, Aldosterone Synthesis

  • See Also
  1. Adrenal Gland Physiology
  2. Serum Cortisol
  • Physiology
  • General
  1. Images
    1. AdrenalFunction.png
  2. Cholesterol is precursor for 5 steroid Hormone classes
    1. Progestagens (e.g. Progesterone)
    2. Glucocorticoids (e.g. Cortisol)
    3. Mineralcorticoids (e.g. Aldosterone)
    4. Androgens (e.g. Testosterone)
    5. Estrogens
  3. Synthesis sites
    1. Adrenal Cortex: Glucocorticoids, Mineralcorticoids
    2. Women
      1. Corpus luteum: Progestagens
      2. Ovary: Estrogens
    3. Men
      1. Testis: Testosterone
  • Physiology
  • Step 1 (Steroid Synthesis - Cholesterol to Precursors)
  1. Cholesterol converted to Pregnenolone
    1. Stimulated by ACTH release from anterior pituitary
    2. Key enzyme: Desmolase (Cholesterol side chain cleavage enzyme)
    3. Inhibitors: Aminoglutethimide (Aromatase Inhibitor), Mitotane, Ketoconazole
  2. Pregnenolone converted to Progesterone
    1. Pregnenolone is precursor of all steroids
    2. Key enzyme: 3-B-Hydroxysteroid Dehydrogenase
    3. Inhibitors: Mitotane
  3. Progesterone converted to 17-a-hydroxyprogesterone
    1. Key enzyme: 17-Hydroxylase
    2. Inhibitors: Abiraterone acetate (Zytiga), Etomidate, Ketoconazole
    3. 17-a-hydroxyprogesterone is precursor
      1. Cortisol Synthesis (Go to step 2)
      2. Aldosterone Synthesis (Go to Step 4)
  4. 17-a-hydroxyprogesterone converted to Androstenedione
    1. Key enzyme: 3-B-Hydroxysteroid Dehydrogenase
    2. Androstenedione is sex Hormone precursor (see Step 3)
      1. Estrone
      2. Testosterone
      3. Estradiol
  • Physiology
  • Step 2 (Cortisol Synthesis from 17-a-hydroxyprogesterone)
  1. 17-a-hydroxyprogesterone converted to 11-Deoxycortisol
    1. Key enzyme: 21-Hydroxylase
    2. Most common enzyme deficiency in steroid synthesis
      1. Congenital Adrenal Hyperplasia (with Virilization)
  2. 11-Deoxycortisol converted to Cortisol
    1. Key enzyme: 11B-Hydroxylase
    2. Inhibitors: Etomidate, Ketoconazole, Metyrapone, Mitotane
    3. Enzyme deficiency related condition
      1. Congenital Adrenal Hyperplasia (with Virilization)
  1. DHEA to Testosterone or Estradiol
    1. Enzyme: 17B-Hydroxysteroid Dehydrogenase
  2. Testosterone to Dihydrotestosterone (DHT)
    1. Enzyme: 5a Reductase
    2. Inhibitors: 5a-Reductase Inhibitor (e.g. Finasteride)
  3. Estrogens from Androstenedione
    1. Androstenedione converted to Estrone or
    2. Androstenedione converted to Testosterone
      1. Testosterone converted to Estradiol
  1. Progesterone converted to 11-Deoxycorticosterone
    1. Key enzyme: 21-Hydroxylase
  2. 11-Deoxycorticosterone converted to Cortisosterone
    1. Key enzyme: 11-Hydroxylase
  3. Corticosterone converted to Aldosterone
    1. Key enzyme: Aldosterone synthase
    2. Inhibitors: Metyrapone, Mitotane
  4. Aldosterone
    1. See Sodium and Water Homeostasis
  • Pathophysiology
  1. Aldosterone
    1. Hyperaldosteronism
  2. Cortisol
    1. Addison's Disease (Adrenal Insufficiency)
    2. Cushings Disease
  3. Androgens
    1. Congenital Adrenal Hyperplasia
      1. 21-Hydroxylase deficiency is most common
  4. Epinephrine and Norepinephrine (Adrenal Medulla)
    1. Pheochromocytoma