Endocrine Principles

Endocrine Principles

1. 3 types of hormones

   • Amines; tyrosine-derived
     • Catecholamines (water-soluble)
     • Thyroid Hormones T3/4 (hydrophobic)
   • Peptides (basically all other hormones)
     • Hypothalamic hormones (except dopAMINE)
     • Pituitary hormones
     • GIT hormones
   • Steroids (cholestrol derivative)
     • Sex Hormones (androgens)
     • Adrenal Cortex Hormones; Aldosterone + Cortisol + androgens
     • Renal 1,25-Dihydroxycholecalciferol

2. 3 stimuli for hormone secretion

   • Tropic Hormones
     • Hormones that stimulate hormone secretion. Eg: hypothalamic or pituitary hormones.
   • Plasma levels of minerals, glucose, hormones.
     • Since most hormones regulate the levels of salt, sugar, and functional hormones in the body, thus their levels are homeostasically intertwined with (and regulated by) them.
   • Neurotransmitters
     • Involvement of the CNS indicates that hormone secretion is also regulated by thoughts, emotions, or autonomic signals etc.

3. Clearance

   • Rate of removal of hormone from the blood; metabolic clearance rate = Rate of disappearance from blood / Plasma concentration of hormone
   • 3 types
     • Renal Excretion
     • Hepatic modification or excretion into bile
     • Interstitial/Intercellular metabolism

4. Permisiveness

   • Some hormones cause up-regulation of receptors and intracellular signaling proteins for another hormone, creating a greater than normal sensitivity to that other hormone's stimulatory function.
   • Ex: Thyroid hormones up-regulate B-Adrenergic receptors for catcholamines, enhancing their effects in the body.