Exam

Steroid Hormone Pathway

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

  • Physiology
  1. 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
  2. Synthesis sites
    1. Adrenal cortex: Glucocorticoids, Mineralcorticoids
    2. Women
      1. Corpus luteum: Progestagens
      2. Ovary: Estrogens
    3. Men
      1. Testis: Testosterone
  3. Conditions related to enzyme deficiencies
    1. Congenital Adrenal Hyperplasia
      1. 21-Hydroxylase deficiency is most common
  1. Cholesterol converted to Pregnenolone
    1. Stimulated by ACTH release from anterior pituitary
    2. Key enzyme: Desmolase
  2. Pregnenolone converted to Progesterone
    1. Pregnenolone is precursor of all steroids
    2. Key enzyme: 3-B-Hydroxysteroid Dehydrogenase
  3. Progesterone converted to 17-a-hydroxyprogesterone
    1. Key enzyme: 17-Hydroxylase
    2. 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
  • 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: 11-Hydroxylase
    2. Enzyme deficiency related condition
      1. Congenital Adrenal Hyperplasia (with Virilization)
  3. Cortisol
  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