L6 Flashcards
What are the 2 types of sex hormones
- Sex steroid hormones
2. Sex peptid hormones
What are the 4 sex steroids? List their common precursor, the family they belong in, where they are found, and what receptor they bind to
All sex steroids derived from master precursor CHOLESTEROL, which is then converted into PREGNENOLONE by CYP450 and then to each sex steroid
- Progesterone
- Belongs to progestin family
- Binds progesterone receptor
- Produced in ovary, placenta - Estradiol
- Belongs to estrogen family
- Binds to estrogen receptor
- Produced in ovary, placenta - Testosterone
- Belongs to androgen family
- Binds to androgen receptors
- Produced in testes - Dihydrotestosterone
- Belongs to androgen family
- Binds to androgen receptors
What are Steroidogenic cell types
steroidogenic cell types are cells that convert cholesterol into pregnenolone (first common step in production of steroid hormones)
Where are steroidogenic cells located?
Adrenal cortex, ovary, testes
Where does cholesterol come from in steroidogenic cells?
- Has some capacity for cholesterol synthesis
- Can obtain cholesterol from VLDL and LDL in bloodstream via LPL activity
Why are steroid hormones not regulated at the lvl of secretion?
Regulation occurs at the LVL of UPTAKE, MOBILIZATION and SYNTHESIS of CHOLESTEROL and at the level of STEROIDOGENIC ENZYME expression
Where do steroidogenic enzymes reside
Inner mta membrane and membrane of SER
Example of how numerous cell types are involved in final conversion to active steroid hormone
Testes secrete little estrogen, but muscle and adipose express enzymes that convert T to estradiol
The overall production of steroid hormone X is equal to
Sum of secretion of steroid hormone X and peripheral conversion from another type of steroid/precursor
How do steroids travel in the blood? Since its traveling in circulation, how will the hormone go to the correct cell
- Lipophylic/hydrophobic so need carrier protein like albumin or sex hormone binding globulin (SHBG)
- Only receptors that express the required receptor will respond to a given steroid hormone
What is peripheral conversion?
Converting one type of hormone to another, away from the site of production
Describe sex steroids
1) Hydrophobic/philicity
2) Storage
3) GI absorption
4) Excretion
1) Hydrophobic/philicity
- HydroPHOBIC/Lipophilic
- Readily diffuses across cell membrane
- Poorly soluble in blood
- Lipophilic binding proteins: albumin, SHBG
2) Storage
- Not stored, excreted once made
- Large secretory capacity
3) GI absorption
- Steroid hormones can be administered orally as they’re relatively easily absorbed e.g. hormone replacement therapy
4) Excretion
- Conjugate hormone with glucuronide or sulfate in the liver will cause inactivation and improves water solubility for excretion by kidney
Using a diagram, draw and describe the mechanism of action of sex steroids
- Lipophilic sex steroid hormone will diffuse across target cell’s membrane.
- Either bind to cytoplasmic receptor (then go to nucleus) or go the the nucleus and bind to nuclear receptor; both cases form hormone-receptor complex.
- Hormone-receptor complex will bind to hormone response element on DNA and alter gene expression through transcription, translation, and synthesis of new proteins.
Describe peptide sex hormones
1) Hydrophobic/philicity
2) Storage
3) Half life
1) Hydrophilic/soluble in plasma
- Examples are anterior pituitary TROPIC hormones
- may appear in urine in a biologically active form (e.g. FSH and LH)
2) Storage
- Stored in vesicles as PROHORMONES
- Released upon stimulus
- Large secretory capacity
3) Half life
- Short (vs. steroid hormones which are bound to carriers so longer half life)
Describe the posterior pituitary gland and the hormones it releases
- Called neurohypophysis cause extension of hypocampal neurons
- Releases 2 neurohormones: oxytocin and ADH
- Magnocellular are large neurons in hypothalamus that synthesize oxytocin and ADH and transport them down their axons to PP for release
