Endocrinology Book

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Steroid Hormone Pathway

Aka: Steroid Hormone Pathway, Sex Hormone Synthesis, Cortisol Synthesis, Aldosterone Synthesis
  1. 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
  2. Step 1: Steroid Synthesis - Cholesterol to Precursors
    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
  3. 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
  4. Step 3: Sex Hormones from Androstenedione
    1. Androstenedione converted to Estrone or
    2. Androstenedione converted to Testosterone
      1. Testosterone converted to Estradiol
  5. Step 4: Aldosterone from Progesterone
    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

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