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234 Cards in this Set
- Front
- Back
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where is the thyroid gland located?
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just below the cricoid cartilage, two lg lobes lie on either side of the trachea
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what are the two lg thryoid lobes of the trachea connected by?
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an isthmus
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what is normal wt of thyroid gland?
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15-20grams
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T or F compared to most other body tissues the thryoid gland is relatively overlyperfused
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True-it has high rate of blood flow
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what kind of innervation does thryoid gland have?
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sympathetic and parasympathetic innervation
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what nerves lie close to the thryoid gland?
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-RLN
-external(motor) branch of superior laryngeal nerve |
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Does thryoid gland have somatic innervation?
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No
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what is potential consequency of thyroid surgery?
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injury to RLN and SLN
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what are the functional units of the thyroid?
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the follicles
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what does interior of follicles contain?
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a glycoprotein colloid called thyroglobulin
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where are thryoid horomones stored?
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stored w/in the thyroglobulin molecules
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each follice is surrounded by what?
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an extensive capillary network
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the two horomones produced by thyroid gland are derivatives of what?
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the AA tyrosine and both contain iodine
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what are the two horomones produced by thyroid gland?
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-Thyroxine (T4)
-Triiodothyronine (T3) |
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what horomone makes up 90% of thyroid horomones secreted by thyroid gland?
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Thyroxine (T4)
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what horomone contains 3 iodine atoms?
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Triiodothyronine (T3)
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what horomone is more potent T3 or T4?
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T3 is about four times more potent than T4
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circulating T4 is converted to what?
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T3 in target tissues
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what tissues are influenced by thyroid horomones?
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nearly all tissues
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when is thyroid horomone absolutely required?
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at critical times of development of nervous systems-fetus and first year after birth
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normally iodide is conc. about ____fold?
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30 fold
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when thyroid is maximally stimulated the iodide conc w/in follicle may reach how many times that of plasma?
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250
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iodide uptake can be blocked by certain anions like what?
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-thiocyanate
-perchlorate |
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thyroglobulin is what kind of protein and is synthesized where?
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-polypeptide
-synthesized in rough ER |
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each thyroglobulin molecules contain how many tyrosine residues and have MW of what?
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-140 tyrosine residues
-MW= 335,000 |
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thyroglobuline is packaged in vesicles in where?
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golgi apparatus
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where is thyroglobulin released into what and secreted into the follicle interior by what?
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cytoplasm
exocytosis |
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iodide is catalyzed by what enzyme?
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peroxidase
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perioxidase does what?
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oxidizes iodide ions to atomic iodine
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what is organification?
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process where binding of atomic iodine to tyrosine residues in thryoglobulin
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tyrosine residues are iodinated to either what?
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MIT (one iodide added)
DIT (two iodide added) |
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MIT + DIT=?
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T3
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DIT + DIT=?
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T4
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typically enough thyroid horomone is stored to meet requirements for how long?
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2-3 months
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is thyroglobulin secreted into the circulation?
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No
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what transports stored thyroglobulin into the follicular cell?
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Pinocytosis
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what fuse w/ the pinocytic vesicles?
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lysosomes
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what digests the thyroglobulin molecules and release T4 and T3?
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Proteases
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secretion of thyroid horomones is stimulated by what?
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TSH (thyrotropin)
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where is TSH released from?
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anterior pituitary
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thyroid horomones are water soluable or lipid soluble?
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lipid soluble
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what are the proteins dedicated to carrying T4 and T3?
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-Thyroxine-binding globulin (80%)
-Thryoxine-binding prealbumin (15%) -serum albumin (5%) |
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what is T1/2 of T4?
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about one week
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what is T1/2 of T3?
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about one day
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thyroid horomones cause what of many genes?
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transcription
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T3 binds to nuclear receptors and stimulates what synthesis (transcription)?
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mRNA synthesis
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what (translation) follows in the ribosomes?
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Protein synthesis
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thyroid horomones allows what horomone to exert its effect on skeletal growth?
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growth horomone
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can thyroid horomone cross BBB?
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yes
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hyperthyroidism in adult can cause what?
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-increased excitability
-irritability -restlessness -insomnia -anxiety -psychosis |
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hypothyroidism can cause what?
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-listlessness
-slowness of speech -impaired memory -dulled mental capacity -somnolence -increased reflex time (slowing of reflexes) |
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TH may increase number of what receptors ?
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beta-adrenergic receptors
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excess TH can exaggerate what responses?
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sympathetic responses mediated via beta-adrenergic receptors
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what are used in tx of thyroid storms?
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beta-blockers
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what is very sensitive to TH?
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basal metabolic rate (BMR)
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TH stimulates rate of O2 consumption in all tissues except?
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-brain
-testes -spleen |
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hypothyroidism causes what?
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decrease tolerance to cold
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hyperthyroidism causes what?
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increased heat production, sweating
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calorigenic effect of TH may result from increased synthesis of cellular enzymes such as?
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Na+, K+-ATPase
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TH does what to carbohydrate metabolism?
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accelerated by TH
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TH does what to glycolysis?
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increase glycolysis in liver, muscle, and fat
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what is glycolysis?
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process by which glucose is broken down
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what does TH do to glycogenolysis and gluconeogenesis?
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increases
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what does TH do to glucose absorption?
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increase glucose absorption from GI tract
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TH does what to lipolysis and cellular oxidation?
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promotes lipolysis and cellular oxidation of fatty acids
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What does TH do to plasma cholesterol?
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decreases-increased hepatic uptake of LDL cholesterol and cholesterol excretion in teh bile
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How does TH affect protein metabolism?
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-stimulates protein synthesis
-excess TH can accelerate protein degradation and reduce body muscle mass |
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TH deficiency causes extracellular accumulation of what?
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proteoglycans and water
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what is an accumulation of proteoglycans and water known as?
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myxedema
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what does TH do to CO?
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increases CO d/t increase in HR
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what happens to skin blood flow and tissue blood flow w/ TH?
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-tissue blood flow increases secondary to TH mediated vasodiltion
-skin blood flow increases for heat elimination |
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all effects of TSH on the thyroid gland are mediated via what?
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cyclic AMP
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TSH secretion from pituitary thyrotropes is stimulated by what?
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hypothalamic thyrotropin-releasing horomone (TRH)
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TSH is inhibited by what?
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somatostatin
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an increase in TH leads to what w/ TSH?
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decrease TSH
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TH inhibits TRH secretion by what?
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the hypothalamus
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what are among the most prevalent of endocrine diseases?
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thyroid disorders
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what are causes of hyperthyroidism?
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-grave's disease
-toxic mutinodular goiter -thyroid (toxic) adenoma -TSH-secreting ant. pituitary tumors -thyroiditis -overdose of synthetic TH |
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grave's disease is an autoimmune disease that does what?
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-thyroid stimulating immunoglobulin (TSI) stimulates TSH receptors
-enlarged thyroid (goiter) and hyperplasia of follicle cells -elevated TH levels, but very low or absent TSH |
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what are symptoms of Grave's disease?
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-heat intolerance
-increased sweating -weight loss -insomnia -tachycardia -exophthalmos |
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emergency surgery should be proceeded by administration of what?
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-PTU- prophylthiouracil
-ipodate -corticosteroid -beta-blocker |
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what should you closely monitor intra-op?
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-CV function
-body temp |
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exopthalamus increases risk of what?
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coroneal abrasion-protect eyes
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what is a good induction agent for hyperthyroid issues?
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Thiopental-has some antithyroid activity
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what are some drugs that stimulate SNS and should be avoided on pts w/ thyroid issues?
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-ketamine
-pancuronium -ephedrine |
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thyrotoxicosis is assoc. w what?
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increased incidence of myopathies and myasthenia gravis
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how is MAC affected by volatile agents?
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MAC is not affected by hyperthyroidism
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what is greatest post-op concern in pts w/ hyperthyroidism?
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thyroid storm
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what does treatment of thyroid storm include?
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-cooling
-hydration -propranolol -PTU -iodide -cortisol |
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what are other complications of cocern of thyroid surgery?
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-bilateral recurrent laryngeal nerve palsy-stridor; laryngeal obstruction
-hypocalcemic tetany secondary to inadvertent removal of the parathyroid glands |
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what are possible causes of hypothyroidism?
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-thyroid ablation by radioactive iodine or surgery
-autoimmune injury (Hashimoto's thyroiditis) -antithyroid drugs (used to tx hyeprthyroidism) -endemic goiter d/t iodine deficiency |
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what are s/s of hypothyroidism?
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-fatigue, sluggishness, somnolence, mental slowing, depression
-bradycardia and decreased CO -slowed reflexes -wt gain, cold intolerance -myxedema |
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what is rare form of coma from hypothyroidism?
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Myxedema coma
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what is s/s of myxedema coma?
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-hypoventilation
- hypothermia - hyponatremia (SIADH) -CHF -delerium |
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who are myxedema coma more common in?
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-elderly women w/ long standing hypothyroidism; mortality >50%
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how do you treat myxedema coma?
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-tx w/ IV thyroxine
-hydration -correction of electrolyte imbalance -temp regulation -stabilization of CV fxn |
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what is d/t thyroid deficiency in fetus or neonate?
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Cretinism
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what happens w/ cretinism?
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-skeletal growth is inhibited more so than soft tissue growth-causes disproportionate appearance (stocky, short indiv)
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what are some pre-op concerns w/ hypothyroidism?
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-avoid pre-op sedation-increased sensitivity to sedative and opioids
-render euthyroid first -pt may have enlarged tongue-could complicate endotracheal intubation |
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pts w/ hypothyroidism have what happen to hypoxic drive?
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-diminished or absent hypoxic ventilatory drive and are predisposed to drug-induced resp depression
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what happens to gastric emptying w/ pts w/ hypothyroidism?
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prolonged gastric emptying time; premedication w/ H-2 receptor blocker and metoclopramide are appropriate
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what is recommended for induction of pt w/ hypothyroidism?
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ketamine
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is MAC affected by volatile agents in pts w/ hypothyroidism?
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Not affected-but onset of action may be faster b/c decrease CO can enhance onset of action of volatile agents
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do you need to monitor neuromuscular blockade in pts w/ hypothyroidism?
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yes, pts have reduced muscle activity and slowed drug metabolism
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what agent should you use to treat hypotension in pts w/ hypothyroidism?
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ephedrine or epi
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what do thiomides do?
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block iodination (inhibit peroxidase enzyme) and coupling of iodinated tyrosines
-first line agent for treating hyperthyroidism |
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what agents competitivly inhibit iodide uptake?
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Thiocyanate, perchlorate
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what is impaired w/ Thiocyanate?
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thyroglobulin synthesis is not blocked, but iodination and formation of TH is impaired
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what is possible adverse effect of Perchlorate?
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aplastic anemia
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what drug may be used to prevent increased thyroid uptake of iodide and hyperthyroidism in pts w/ treated amiodarone?
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Perchlorate
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what agent is commonly administered to treat hyperthyroidism?
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iodide
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what do high blood concentrations of iodide do?
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-inhibit organification and TH release
-thyroid size and vascularity are also reduced |
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what does radioactive iodine do?
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acts to destroy thyroid tissue
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how do beta-adrenergic antagonists work in thyrotoxicosis?
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-block enhanced sympathtetic activity characterisitc of thyrotoxicosis
-inhibit peripheral conversion of T4 to T3 |
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adrenal glands are essential for what?
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life (homeostasis)
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what are essential for maintenance of ECF volume?
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mineralcorticoids
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loss of mineralcorticoids can cause death in 1-2 wks d/t what?
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sodium loss
hypovolemia cardiovascular collapse (shock) |
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what influences metabolism?
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Glucocorticoids
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what frequently function together to provide adaptation to stress?
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adrenal cortex and medulla
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the medullary horomones provide for what?
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rapid phsyiological adjustments to stress
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which horomones are slower acting?
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cortical horomones
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where are adrenal glands located?
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superior poles of the kidneys
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what is mass of each adrenal gland?
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weighs approx 4g
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medulla is approx what % of the adrenal gland and what do they secrete?
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-20%
-epi, norepi, dopamine |
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what are three regions of cortex?
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-glomerulosa
-fasciculata -reticularis |
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what is outerlayer of cortex? and what does it secrete?
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glomerulosa; secretes aldosterone
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what is middle layer of adrenal cortex? and what does it secrete?
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fasciculata; secretes cortisol and androgens
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what is inner layer of adrenal cortex and what does it secrete?
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reticularis; secretes cortisol and androgens
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what are all steroids and synthesized from cholesterol?
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adrenocortical hormones
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LDL cholesterol is taken up from what?
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the plasma via cell membrane LDL receptors
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cholesterol is initially converted to what?
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pregnenolone (rate limiting step)
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corticosteroids circulate in blood bound partly to what?
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corticosteroid binding globulin
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what is T1/2 of cortisol?
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60-90 min
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what is T1/2 for aldosterone?
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15-30min
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what is responsible for 90% of adrenal mineralcorticoid activity?
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aldosterone
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the daily secretory rate of cortisol is about how many times that of aldosterone?
|
80-100 times, cortisol is much weaker but is produced in much greater amts
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what are other mineralocorticoids?
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deoxycorticosterone, and corticosterone
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what are the actions of aldosterone in CCT?
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-promotes Na+ reabsorption
-promotes K+ secretion and excretion -promotes H+ secretion and excretion |
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what is mechanism of aldosterone action in principle cells?
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-diffusion into the tubular cell and binding to a cytoplasmic receptor
-stimulation of mRNA synthesis (transcription) -stimulation of protein synthesis (translation) |
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what regulates aldosterone secretion?
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-extracellular K+ conc-direct relationship
-angiotensin II- direct effect -ACTH |
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what is normal secretory rate of aldosterone?
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100-200micrograms/d
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nearly all (95%) of glucocorticoid activity of the adrenal gland is d/t what?
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cortisol
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what kind of effect of coritsol occurs on CHO metabolism?
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hyperglycemic action
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what kind of effects from cortisol occur on protein metabolism?
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-reduction in protein stores in nearly all cells (xcept hepatocytes)
-decreased protein synthesis (decreased RNA) -increased protein catabolism |
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AA released from muscle and other tissues are delievered to the liver and used for?
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-increased hepatocyte protein synthesis, incl plasma proteins
-gluconeogenesis |
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what are the effects of cortisol on fat metabolism?
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-mobilization of fatty acids from adipocytes
-increased fatty acid oxidation in cells for synthesis of ATP |
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what are some aspects of inflammatory response may actually cause or exaggerate tissue injury?
|
-release of lysosomal enzymes
-release of chemical mediators (ex superoxide, eicosanoids,histamine, cytokines, lymphokines) |
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glucocorticoids block what?
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phospholipase A2 and thus block the production of pro-inflammatory eicosanoids
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glucocorticoids suppress what function?
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macrophage fxn and T cell proliferation
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chronic administration of synthetic glucocorticoids can cause what?
|
severe immunosupression,
-and predispose to fatal infections, & can suppress the pituitary and adrenal cortical response to stress |
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what is most important factor for regulation of cortisol secretion?
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ACTH (adrenocorticotropin horomone)
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where is ACTH released from and stimulated by?
|
anterior pituitary, stimulated by corticotropin releasing horomone (CRH)
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cAMP stimulates what?
|
-uptake of LDL by cholesterol by cell
-release of cholesterol from intracellular stores -synthesis of cortisol from cholesterol |
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what exerts negative fdbk inhibition of CRH release and inhibits CRH action on ant pituitary corticotropes?
|
cortisol
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what are also known as 17-keto steroids?
|
androgens
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what are main adrenal androgens?
|
-dehydroepiandrosterone (DHEA)
-androstenedione |
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some of secreted androstenedione is converted to what?
|
testosterone in extra adrenal tissues
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what is primary adrenal insufficiency?
|
addisons disease
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what are some causes of addison's disease?
|
-autoimmune destruction of adrenal tissue
-tuberculosis -cancer -heparin induced thrombocytopenia |
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s/s of decreased cortisol?
|
hypoglycemia btwn meals
anemia lethargy anorexia |
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s/s decreased aldosterone for addison's?
|
hyponatremia
hypovolemia hypotension hyperkalemia acidosis |
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what are s/s decreased 17-ketosteroids w/ addisons?
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loss of muscle mass
weakness reduced libido |
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what does secondary adrenal insuff result from?
|
insufficient secretion of ACTH
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what is usual cause of secondary AI?
|
chronic synthetic glucocorticoid therapy for inflammtory diseases like asthma or RA
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what is medical mngt of AI include?
|
-hydrocortisone to tx glucocorticoid deficiency
-fludrocortisone to tx mineralocorticoid def. |
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what are clinical presentations of addisonian crisis?
|
severe N/V
abd pain weakness hypovolemia hypotension |
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what is mngt of addisonian crisis?
|
IV glucocorticoids and NS
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does a pt taking <5mg/day of pred. require periop glucocorticoid supplementation?
|
No
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what pts are at risk and considered to have adrenal suppression?
|
-glucocorticoid doses equiv to >20mg/day of pred for >3wks during past year-peri-op glucocorticoid supplemenation is warranted
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what drug should be avoided in pts with AI and why?
|
Etomidate; causes transient suppression of cortisol synthesis
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what is Cushing's syndrome?
|
excess glucocorticoid
|
|
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what are two causes of Cushing's
|
1-ACTH dependent
2-ACTH independent |
|
|
what are s/s of cushing's syndrome?
|
-muscle weakness d/t increased muscle protein catabolism
-osteoporosis -poor wound healing -increased susceptibility to infection -abnormal fat distribution -thinning of skin; purple striae -hyperglycemia -hypokalemic metabolic acidosis -hypervolemia -HTN |
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what are some anesth. considerations w/ cushings?
|
-correct fluid and electrolyte disturbance w/ supplemental potassium and spironlactone
|
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what is primary aldosteronism resulting from a glomerulosa tumor secreting excess amts of aldosterone?
|
Conn's syndrome
|
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what are s/s of Conn's syndrome?
|
-hypervolemia
-low renin HTN -hypokalemia -muscle weakness -metabolic alkalosis |
|
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what is diagnositc criterion for Conn's syndrome?
|
HTN w/ increase aldosterone and low renin level
|
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what does pre-op preparation of Conn's include?
|
supplemental potassium
spironlactone and tx of HTN |
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what is a chromaffin tissue tumor?
|
Pheochromocytoma
|
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where do 80% of pheochromocytoma tumors occur?
|
adrenal medulla
|
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what are triad hallmark s/s of pheochromocytoma?
|
-paroxysmal HTN
-HA -sweating also hypovolemia, nervousness, and anxiety |
|
|
what is used for pre-op BP control of pheochromocytoma?
|
-alpha adrenergic blockade (phenoxybenzamine)
-beta blockade (propranolol) or a Ca+ Ch. blocker or an ACE |
|
|
what agents can be used to tx intraop HTN w/ pheochromocytoma?
|
-Nitroprusside
-phentolamine -nicardipine |
|
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what are agents that should be avoided in pts w/ pheochromocytoma?
|
agents that enhance SNS activity like
-ephedrine -ketamine -pancuronium or cause histamine release -atracurium, MS |
|
|
what has been recommended to minimize hypotension prior to venous ligation of pheochromocytoma?
|
-volume expansion w/ LR or NS to a PAWP of 16-18 mmHg
|
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|
what is a chemical substance produced by an endocrine gland or by specialized cells in an organ?
|
horomone; circulates in blood to act at another site or other sites in the body
|
|
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what is an autocrine substance?
|
chemical substance secreted by particular cell types; acts locally on the cells producing it
|
|
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what is a substance secreted by particular cell types; acts on neighboring cells?
|
Paracrine substance
|
|
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what are peptide substances secreted by phagocytes, lymphocytes, and other cell types?
|
cytokines
|
|
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what are classifications of horomones?
|
1-steroid horomone
2-peptides/polypeptides 3-derivatives of Tyrosine |
|
|
all endogenous steroids are derived from what?
|
cholesterol
|
|
|
what are ex. of steroid horomones?
|
adrenal cortical horomones
sex horomones |
|
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what horomones are synthesized by ER/ GOlgi apparatus?
|
peptides/polypeptides
ex: pit. horomones, pancreatic horomones |
|
|
where are derivatives of tyrosine stored? and what are examples
|
w/in endocrine cells
ex thyroid horomones, adrenal medullary horomones |
|
|
what are mechanisms of hormone action?
|
-act on target tissues
-receptors |
|
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what is a hormone receptor in cell membrane?
|
G protein coupled receptor
|
|
|
what are the responses of hormones to receptor binding?
|
-change in membrane permeability
-activation of intracellular enzymes -production of intracellular second messenger -gene activation and protein synthesis |
|
|
where does pituitary gland lie?
|
in sella turcica just below hypothalamus
|
|
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how is pituitary gand connected to hypothalamus?
|
via infundibulum
|
|
|
what is post lobe of pituitary gland called?
|
neurohypophysis (neural tissue)
|
|
|
what is ant. lobe of pituitary gland called?
|
adenohypophysis (glandular tissue)
|
|
|
what lobe contains nonmyelinated nerve fibers?
|
post lobe of pituitary
|
|
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where do cell bodies of post lobe of pituitary lie?
|
in paraventricular and supraoptic nuclei of hypothalamus
|
|
|
the nerve terminals of post. lobe of pituitary store and release what two major horomones?
|
-ADH
-Oxytocin |
|
|
how is ant lobe of pituitary connected to hypothalamus by?
|
hypothalamic-hypophyseal portal blood vessels
|
|
|
what are the chemical substances released by neurosecretory cells of hypothalamus known as?
|
hypophysiotropic hormones
|
|
|
where do hypophysiotropic hormones act on?
|
the glandular cells of ant pituitary
|
|
|
what does ant pituitary do?
|
synthesizes, stores and secretes 6 major hormones
|
|
|
what are 6 secreted hormones known collectively as?
|
trophic hormones
|
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what are the 6 hormones secreted from ant pituitary?
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1-GH or somatotropin
2-TSH or thyrotropin 3-adrenocorticotropic hormones (ACTH) or corticotropin 4-gonadotropins -FSH -LH 5-Prolactin |
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what are the hormones released from neurosecretory cells of the hypothalamus?
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hypophysiotropic horomones
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what is most abundant of the pituitary trophic hormones?
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GH (accounts for about 10% of dry wt of ant. pit)
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what is GH aka ?
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-somatotropin or somatotropic hormone
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what are teh effects of GH?
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-stimulates growth of nearly all body tissues
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growth promoting actions of GH are mediated by what?
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somatomedins (sm polypeptides released from the liver in response to GH)
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what is most important of Somatomedins?
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Somatomedin C (Sm-C)
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What are effects of metabolism of GH on protein?
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-stimulates AA uptake by cells
-stimulates protein synthesis and decreases protein catabolism -stimulates RNA production |
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what does GH do to carbohydrate?
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-decreases insulin sensitivity of and glucose uptake by muscle and adipose tissue
-promotes hepatic glucose production |
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what does GH do to lipogenesis?
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inhibits
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GH is protein-sparing and has what kind of effect on metabolism?
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diabetogenic effect
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what stimulates GH secretion?
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GHRH
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what inhibits GH secretion?
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Somatostatin (SRIF)
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hypoglycemia does what to GH secretion?
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stimulates GH secretion
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hyperglycemia does what to GH secretion?
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inhibits
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what are the certain AA that stimulate GH secretion?
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arginine and leucine
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what does Sm-C stimulate and inhibit?
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stimulates: somatostatin release from hypothalamus
inhibits: pit. response to GHRH |
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what are the pituitary dysfunctions?
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-Central DI
-Cushing's disease -Acromegaly |
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what results from overproduction of GH in adults?
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acromegaly
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what are signs of acromegaly?
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-abnml thickening of hands, feet, nose, cranium, mandible and vertebrae
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what are freq. complications of acromegaly?
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HTN
glucose intolerance DM |
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what can reduce symptoms in many pts w/ acromegaly?
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somatostatin analogue: octreotide
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what surgery is usual technique to remove the tumor of pituitary?
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transsphenoidal surgery
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what are some anesthesia concerns of acromegaly?
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-macroglossia and hypertrophy of epiglottis and pharyngeal tissue
-glottis and subglottic area may be narrowed -approx 50% of pts will have inadequate collateral blood flow through ulnar artery in one or both hands |
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ingestion of lg amts of liqorice can cause some s/s Conn's syndrome why?
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Glycyrrhizonic acid-steroid like glycoside has well known mineralcorticoid activity
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