What is physiology?
• A. Study of function in living matter
• B. Specific characteristics and mechanisms of the human body that make it a living being
• C. “The human being is actually an automaton.”
• D. All of the above.
Learning Objectives
• Explain normal feedback mechanisms for normal endocrine function
• Describe abnormal pathophysiologic states
• Define treatment approaches for such states
Ground Rules
• Case-based, common examples
• Feel to ask questions anytime
• Take a few breaks for Q and A
• Call or e-mail [[email protected]] with confused thoughts, concepts, etc.
Major Areas
• Thyroid gland
• Adrenal gland function, steroid Rx
• Diabetes: glucose monitoring, insulin Rx
• Calcium homeostasis, vitamin D
• Pheochromocytoma
• Diabetes insipidus
Design Exercise
• New heat source for your house in the basement
• Need monitor system 3 floors above
• Thermostats not invented yet!
• Task= design system to regulate temperature in your house
Purpose of Endocrine System
• Principally concerned with control of different metabolic functions of the body [e.g., transport of substances through cell membranes]
• Hormonal effects can occur in seconds while others require days or weeks
What is a hormone?
• A chemical substance secreted into body fluids by one cell or group of cells
• Exerts a physiological control effect on other cells in the body
• General vs. local hormones
• General hormones may effect all cells [e.g. GH] or some effect specific tissues
Major Hormones
• Anterior pituitary– Growth hormone– Adrenocorticotropin [ACTH]– Thyroid-stimulating hormone [TSH]– Follicle-stimulating hormone [FSH]– Luteinizing hormone [LH]– Prolactin [PRL]
More Hormones
• Posterior pituitary: antidiuretic hormone [ADH]
• Adrenal– Aldosterone– Glucocorticoids [cortisol]– Testosterone, estrogen– catecholamines
Even More Hormones!
• Thyroid hormones: thyroxine [T4], triiodothyronine [T3]
• Pancreatic: insulin, glucagon
• Parathyroid: parathyroid hormone [PTH]
Chemistry of Hormones
• Two types– Proteins or derivatives of proteins or amino
acids [e.g., anterior pituitary, thyroid]– Steroid hormones [e.g., adrenal cortex, gonads]
• Circulate in minute quantities [e.g., one-millionth of a milligram]
• Bioassay vs. radioimmunoassay
What describes hormones effecting other local cells?
• A. Paracrine
• B. Endocrine
• C. Autocrine
• D. None of the above.
Bioassay
• Animal cell tissue system
• Plasma or some extract added to see effect
• E.g., testosterone
Mechanisms of Action
• Activation of cyclic AMP system of cells• Need hormone receptor [key and lock]• Cyclic AMP forms as an intracellular
hormonal mediator [aka as “second messenger”]
• ACTH, TSH, FSH, LH, ADH, PTH, glucagon
• Effects can be instantaneous
2nd mechanism of action
• Activation of genes in target cells, causing formation of intracellular proteins
• Steroid hormone enters cytoplasm and binds to receptor proteins
• Enters nucleus to activate genes to form messenger RNA
• m-RNA promotes new proteins to be made• Delayed effect of mins [aldosterone] to days
Transport of Hormones
• Biologic effect due to free hormones• Binding globulins – “the buses”
– Thyroid Binding Globulin [TBG]– Sex-hormone Binding Globulin [SHBG]– Cortisol Binding Globulin [CBG]– Produced in liver
• What is assay measuring? “Total” [I.e., bound] vs. “Free”
Sandwich-type assays refer to:
• A. Dialysis method
• B. Ham and cheese
• C. Two antibodies
• D. Live cellular responses
Control of Hormonal System
• Tendency of each gland is to oversecrete
• Need method to prevent oversecretion
• Need method to stimulate production if undersecreting
• KEY is Negative Feedback
• Some exceptions [e.g., prolactotrophs and dopaminergic inhibitory fibers]
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