Endocrinology
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chemical substance that is produced and secreted into the blood by an organ or tissue and that has a specific effect on a target tissue located away from the site of its origin.
Hormone*
Prostaglandins?
-influences neighboring cells -autocrine and paracrine function -very short half-life
Exocrine or endocrine gland? Secretory products are released on to “external surfaces” * e.g. Sweat, Salivary gland
Exocrine gland
Exocrine or endocrine gland? -Secretory products into the “blood stream” -transport them to specific target tissues
Endocrine gland -Upon reaching the specific target * Secretary product alters the function of target cell
❖ Characteristics of endocrine hormones and their effects: Effects are not on and off but graded…
up or down
❖ Characteristics of endocrine hormones and their effects: Secretion is not constant but usually occurs in _______.
pulses -Provocative tests are required (stimulates max release)
❖ Characteristics of endocrine hormones and their effects: Effects of the hormones continue after…
the hormone is gone
❖ Characteristics of endocrine hormones and their effects: Hormones don’t act alone. What are some examples?
blood glucose; insulin and glucagon
❖ Characteristics of endocrine hormones and their effects: Some hormones do similar things at….
different rates Glucagon & cortisol: increases [glucose]blood, glucagon: rapid & temporary v. cortisol: slow & sustained
❖ Characteristics of endocrine hormones and their effects: Some hormones accomplish similar results with different…
tissue specificities -Epi & glucagon on glycogenolysis. Epi: muscle v. Glucagon: best on liver
❖ Characteristics of endocrine hormones and their effects: Sometimes the tissue determines the _________ of the response.
quality ex: EPI- glycogenolysis in muscle( increases glucose) & lipolysis in adipose (increases FA)
❖ Characteristics of endocrine hormones and their effects: Hormone don’t always fit the ________ definition.
classical ex: e.g. ACTH (mostly released in the adrenal glands but also in the brain)
What are the physiologic functions of hormones?
-Maintenance of internal milieu -Production -Growth and Development -Energy Metabolism
How many amino acids are peptides? Proteins?
peptides = <100 proteins = >100
Where does ADH come from?
hypothalamus
Hormone type: -Water soluble and do not require transport proteins -short half-life -synthesized from amino acids
➢Protein /Peptide Hormones e.g. insulin, glucagon
Hormone type: Synthesized from cholesterol * Lipid soluble and require transport proteins – Only free-form is biologically-active * Long half life
Steroid hormones e.g. testosterone, aldosterone
Hormone type: derived from tyrosine
Amino acid-based hormones e.g. Thyroxine, epinephrine (catecholamine)
_____________ stimulates transcription of sodium/potassium ATPase
aldosterone
What causes hormones to have different mechanisms of action?
due to structural and solubility differences.
-large & H2O soluble ➡ tend to remain in the circulation ✴These hormones bind to EXTRACELLULAR RECEPTORS activating a protein cascade ➢ Involves membrane receptor activation & a secondary messenger
Protein-based hormones
Cross membranes –> bind DIRECTLY to their intracellular targets. ✴ Hormone-Receptor complex DIRECTLY activates TRANSCRIPTION.
Steroid hormones: lipophilic
❖ Hormone secretion occurs in _______ or ________ rather than in a continuous, constant manner
bursts, pulses
Only a small portion of the hormone is removed by the target tissue; most are cleared by
the liver or kidneys