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Intro to endo
Terms in this set (40)
Definition of Endocrine
Substances secreted from one organ in one part of the body and have an action on a distant organ, affecting another issue. Ex: TSH from hypophysis acts on the thyroid.
Action on cells in the immediate vicinity of secretion. Ex: somatostatin from delta cells on insulin and glucagon secretion from bet and alpha cells on pancreas.
Action on the same cell. Ex: oncogene products in cancer cells and regular cells.
Substance secreted from an organ into ducts which have actions externally. Ex: pancreatic secretion into GI tract.
Peptide hormone examples
Insulin, TSH, FSH (follicular stimulating hormone)
Lipids in the endocrine system
Steroid hormones and sex hormones derived from cholesterol.
Amino acid analogues in endocrine
Catecholamines and thydoid hormones derived from tyrosine.
What are the functions of the endocrine system componenets?
Sensing, production/storage, secretion.
Sensing in the endocrine system
Needs to know what is in the vicinity and the status of homeostasis to know when to secrete hormones.
Types of production and storage of hormone
Immediate secretion or production and storage. Ex: insulin is stored, steroids are not.
Types of endocrine secretion
Basal (mostly), pulsitile (ACTH, GH, FSH, LH), Non-pulsitile (Circadian), Hormone/pro-hormone.
Circadian hormone secretion
Controlled by internal clock in the hypothalamus and input from internal and extrenal stimuli with the CNS. Ex: ACTH/Cortisol. Secreted most in the morning. Cushing disease: increase in cortisol secretion but also inappropriate times of release during the day (lower when supposed to be high).
Pulsatile hormone secretion
Lutinizing hormone (LH), FSH, and growth hormone (GH). Frequency and amplitude both important. Most important to body is the pulstile nature otherwise no activity. Random tests of hormone don't mean much, need to know rhythms. External stimulus example: exercise and sleep is important for GH. Also GnRH and LH.
GnRH and LH
Control menstruation, sexual activity, testosterone release. Secreted from hypthalamus and affects pituitary gland. GnRH is used to suppress menstruation/ovulation. If no pulsing in GnRH, no pulsing in LH.
Processing of Endocrine System
Transport, metabolism to active form, specific uptake into cells, specific action via specific hormonal receptors, metabolism.
Transport in endocrine system
Proteins to distant area: solubility and buffer action.
Metabolism to active form
Ex: T4 received by tissues and metabolized in peripheral tissues to become T3. Ex2: Testosterone active in most tissues but in some (scrotum) converted to DHT (supertestosterone) for regions that need more testosterone effect.
Specific uptake into cells
Port of entry is specific to the hormone. Can be an active process or by diffusion. Specific action via hormonal receptors.
Regulatory feedback loops of the hypothalamic-pituitary-target organ axis
Neurons stimulate or inhibit pituitary gland to stimulate the target organ (ex: thyroid) by tropic hormones (ex: TSH). Hypothalamus sends releasing factors (GnRH) to stimulate or inhibiting factors to pituitary to stimulate tropic hormones to activate target organ. Target organ then feedsback to pituitary gladn, hypothalamus, and/or neurons.
Purpose of feedback mechanisms
Present in all systems that regulate hormones to maintain homeostasis.
Metabolism of endocrine system
End of process
Prolactin mode of hormone secretion
Daily fluctuation in response to external stimuli. Secreted in reponse to suckling-->expressing milk. Also examination and sex increase prolactin. Important for men and women arousal (but this function not related to suckling).
Types of endocrine regulation
External stimuli (to basal release or circadian rhythm), releasing hormones, feedback inhibition/stimulation.
Function of receptors
Specific binding of hormone. Binding leads to physiologic response. Down regulation (number of receptors variable. Ex: T3-->downregulation of T3 receptors (body controlling amount and effect). Upregulation by same mechanism (same hormone system), control by other hormones (ex: T4 upregulated adrenergic receptors, increased tissue response for catecholamines).
Free hormone to saturate 50% of receptors (Kd). -1/m.
High affinity for specific hormones, low affinity for other molecules.
Definiciency states, hormone excess, Production of abnormal hormones/hormone-like substances, hormone resistance states, diseases affecting multiple endocrine systems (autoimmune polyglandular syndrome, multiple endocrine neoplasia)
Deficiency states of a hormone
1. Why gland stops producing hormone, 2. why organ stops responding (resistance syndromes)
1. gland diseased, 2. annormal hormones with increased function, 3. deficiency in gland (infection/inflammation)
Production of abnormal hormones/hormone-like substances
Something different being produced or other diseases. Ex: oat cell carcinoma in lung produces increased ACTH.
Example of hormone resistance states
Children coming in with high GH and short stature had GH defect: Loron dwarfism (receptor defect)
Autoimmune polyglandular syndrome
Autoimmune endocrine disorders, basic defect causes different hits in multiple targets. Ex: diabetes and parathyroid problems, probably a third problem.
Multiple endocrine neoplasia
Multiple diseases caused by surrounding genetic defects.
Deficiency endocrine disorders
Deficiency state caused by: abnormal gland (primary disorder), abnormal stimulus to gland (secondary and tertiary disorder), abnormal transporters (resistance), abnormal receptors (resistance syndrome), inhibition of function.
Excess hormone disorders
Caused by: overproduction of original gland, overproduction at ectopic site, overproduction in peripheral tissues from circulating precursors, or iatrogenic.
Example of overproduction of original gland
Hyperthyroidism, Cushing, etc.
Overproduction at ectopic site
ACTH secretion from oat cell carcinoma.
Overproduction in peripheral tissues from circulating precursors
Excess estrogen production in cirrhotic liver
Iatrogenic excess disorders example
Epidemic of "hamburger thyroid toxicosis" from slaughterhouse using strap muscle without separating thyroids-->beef with TH. Ex2: gel with testosterone spreads to others by touch if don't wash hands.
Assessment of endocrine status
Most important: evaluate patient by history and physical. Things have to make sense. Then do tests. Measure hormone levels 9serumm vs urine), measure biologic response.
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