Principles of Endocrinology Flashcards
Define Hormone.
A hormone is a substance that is released into the blood in response to a specific stimulus, and acts at a distant target tissue, where it exerts its specific effects.
What are endocrine substances?
Substances released from a gland that act at a remote target tissue.
What are paracrine substances?
Substances released from a gland cell that act on cells in the same gland.
What are autocrine substances?
Substances released from a gland that act back on the same gland.
What are the 4 kinds of hormones?
Protein/Peptide, Steroids, Amine hormones, Eicosanoids.
What are peptide/protein hormones? What are they made from? Where do they have receptors? How do they circulate? Does it exhibit species variation? Example?
Protein hormones are synthesized from AA. They vary in size and exhibit species differences. They have extracellular receptors as they are not lipid soluble. Usually circulate not bound. e.g. Insulin.
What are steroid hormones? What are they made from? Where do they have receptors? How do they circulate? Does it exhibit species variation?
Steroid hormones are made from Cholesterol. They have intracellular receptors, and circulate usually bound to a protein. Usually do not exhibit species differences. Slow acting.
What are the 4 kinds of steroid hormones? Examples?
Corticosteroids (C21), Progesterone (C21), Testosterone (C19), Oestrogens (C18)
What are amine hormones? How can they be separated?
Amine hormones are hormones derived from Tyrosine or Tryptophan. Catecholamines and Thyroid hormones are made from Tyrosine. Indoleamines are made from Tryptophan.
What are Indoleamines hormones? What are they made from? Where do they have receptors? How do they circulate? Does it exhibit species variation? Example?
Indoleamines are made from Tryptophan. They are not lipid soluble, and so have extracellular receptors. No species variation. E.g. Serotonin, Melatonin.
What are Catecholamines hormones? What are they made from? Where do they have receptors? How do they circulate? Does it exhibit species variation? Example?
Catecholamines are made from Tyrosine. They are not lipid soluble, and so have extracellular receptors. They do not exhibit species variation. e.g. Adrenaline, Noradrenaline, Dopamine.
What are Thyroid hormones? What are they made from? Where do they have receptors? How do they circulate? Does it exhibit species variation? Example?
Thyroid hormones are made from Tyrosine. They have intracellular receptors, and usually circulate bound. No species variation. e.g. Triiodotyrosine (T3), Thyroxine (T4)
What are Eicosanoids hormones? What are they made from? Where do they have receptors? How do they circulate? Does it exhibit species variation? Example?
Eicosanoids are derived from Arachadonic acid in the plasma membrane. They act locally, as they have a short half life. Interact with plasma membrane receptors. No species variation. E.g. Prostaglandins, Leukotrienes.
What kind of receptors do prolactin and Growth hormone use? How do these work?
JAK-STAT. Receptor ligand complex recruits second receptor. Dimerised receptor activates JAK. JAK phosphorylates STAT.
How does the secretion of Protein and Steroid hormones differ?
Protein hormones are usually stored in vesicles. Steroid hormones are usually secreted as and when they are needed.