Intro to Endocrinology

Chemical substance that sends a message to another cell in the body

Endocrine: bloodstream Exocrine: GI tract Neurocrine: neurologically Paracrine: interstitial fluid

• Hypothalamus • Pituitary • Thyroid • Parathyroid • Adrenal gland • Pancreas • Ovaries • Testes

• Amine • Peptide • Protein • Glycoprotein • Steroid • Fatty acid

• Trp or Tyr are modified to create amine hormones • Epinephrine, triiodothyronine, thyroxine, serotonin • Very short half-lives

• Chain < 50 aa • Water soluble, don’t cross membranes easily • Must first bind to membrane-bound receptors • Vasopressin and oxytocin

• Chain > 50 aa • ACTH, calcitonin, insulin, glucagon, oxytocin

• Conjugated to carbs • FSH, LH, and TSH • Solubility and half-life similar to protein hormones

• Derived from lipid, usually cholesterol • Hydrophobic, must be transported in blood bound to carrier proteins • Can cross membranes due to lipids • Aldosterone, cortisol, estrogen, progesterone, testosterone, other androgens (DHEA)

• Derivatives of arachidonic acid • Eicosanoids, leukotrienes, prostaglandins, thromboxanes • Rapidly degraded, effective for only seconds

The sum of chemical processes that occur within a living organism to maintain life (catabolism + anabolism)

Creating substances

Breaking down substances

The speed of anabolism or catabolism determines the extent to which hormones are capable of binding to receptors and eliciting effects

• Speed of production or breakdown affects blood hormone levels • Amount of carrier protein affects protein-bound hormone levels • Disease states (e.g., cirrhosis) affect enzymatic hormone breakdown

• Increase testosterone degradation • Leads to cirrhosis, which can cause less albumin and other binding proteins

Many hormones are produced in the adrenal gland by a cascade of enzymatic reactions

Kidney and liver

Blood -> Liver tags certain hormones for destruction or creation of different substances (or kidney)

Inactivating metabolic pathways and excretion in urine or bile

Inactivated by intracellular deiodinases

Rapidly degraded within blood circulation

Rapidly inactivated by metabolism and typically active for a short time period (seconds)

A stimulus will feedback upstream and decrease production of itself (e.g., thyroid)