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endocrine - thyroid
n/a
77
Accounting
Pre-School
03/01/2010

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Term
what are the functions of thyroid hormone?
Definition
increases mitochondrial action, respiratory enzymes, Na-K ATPase and other enzymes --> increases basal metabolic rate, increases o2 consumption, and increases sensitivity of target tissues to catecholamines (elevating lipolysis, glycogenolysis and gluconeogenesis)
Term
how much iodine intake is ideal? what is the level of intake that leads to goiter?
Definition
>200 ug/d is ideal. <50 --> elevation in TSH --> goiter
Term
what abnormalities do children born to women with endemic goiter have?
Definition
mental retardation, abnormalities of hearing, gait, and posture, short stature
Term
what inhibits TSH?
Definition
thyroid hormone, dopamine, glucocorticoids
Term
how does TSH control thyroid hormone production?
Definition
increases iodine trapping (expression of sodium/iodide symporter); increases oxidation (expression of TPO); iodination, secretion of T4/T3 and ratio of how much is secreted.
Term
what does TRH cause an increase in?
Definition
TSH and prolactin
Term
cretinism is caused by?
Definition
iodine deficiency
Term
why would we measure serum thyroglobulin?
Definition
mostly exists in colloid, but its released into circ in small amounts and is used to indicate the presence of thyroid tissue. used to monitor the completeness of thyroid tissue removal during tx of thyroid cancer. absence --> no recurrence of cancer. reappearance --> return of cancer
Term
anti-thyroid drugs work in what stages of thyroid hormone synthesis?
Definition
oxidation (decrease TPO) and decrease coupling of iodotyrosines
Term
what is the wolff chaikoff effect?
Definition
excess of iodine --> inhibits organification of iodine (lasts few days, then organification resumes) used to treat thyroid storm (severe hyperthyroidism) - decreases hormone synthesis acutely while other meds are taking effect
Term
what are the 3 main binding proteins for thyroid hormone?
Definition
thyroid binding globulin, transthyretin, albumin
Term
what things increase thyroid binding globulin?
Definition
pregnancy, estrogen use, acute hepatitis, x-linked familial disorder, phenothiazines (schizo), clofibrate
Term
what things decrease thyroid binding globulin?
Definition
chronic hepatitis, androgens, glucocorticoids, protein loss, phenylbutazone, phentoin (seizures)
Term
what supplies peripheral T3?
Definition
20% released from thyroid as T3; 80% converted peripherally in liver and kidney from T4
Term
describe type 1 de-iodinase
Definition
found in liver, kidney, and thyroid. converts T4 to T3; supplies T3 to the plasma. activity increased by TSH and it influences the amount of T3 produced; activity decreased by PTU and iopanoic acid used in xray contrast
Term
describe type II de-iodinase
Definition
found in brain, pituitary, thyroid, brown fat, placenta, sk m, and cardiac m. converts T4 to T3; supplies T3 for LOCAL use. ensures adequate active hormone in the brain, involved in intracellular production of T3, important in neg FB regulation of TSH.
Term
describe type III de-iodinase
Definition
found in brain, placenta, and skin. converts T4 to rT3 (in malnutrition, illness) and T3 to T2 (inactivates thyroid hormones)
Term
what are the two terms associated with severe hypothyroidism and severe hyperthyroidism?
Definition
severe hypo = myxedematous; severe hyper = thyrotoxic
Term
why can we use beta blockers to treat hyperthyroidism sx (tachy)?
Definition
bc tachycardia is mediated by b-adrenergic stimulation (d/t increased beta receptor concentration or responsiveness)
Term
what is thyroid hormones mechanism of action?
Definition
1. genomic (transcriptional, slow onset) T3 receptors bind DNA with RXRs as heterodimer --> T3 binding to this heterodimer causes coactivation and gene transcription. 2. non-genomic (direct membrane and cytosolic actions, occur within minutes) through P13 kinase. binding causes mitochondrial respiration probably secondary to nuclear effects but possibly direct effects as well
Term
what is T3 resin uptake?
Definition
measure of how many binding sites for T3 (and T4) are available on thyroid binding globulin. (more available binding sites --> lower resin uptake. less available binding sites (thyrotoxicosis) --> increase resin uptake of TH)
Term
what is the most useful tool to distinguish the different causes of hyperthyroidism?
Definition
nuclear scans (they are NOT helpful in dx of hypothyroidism)
Term
what can we treat with radioactive iodine?
Definition
high doses to tx graves disease and toxic multinodular goiters; even higher doses for malignancy
Term
what accounts for 98% of hypothyroidism?
Definition
primary hypothyroidism
Term
what is hashimoto's thyroiditis?
Definition
slow irreversible autoimmune destruction of the thyroid. autoantibodies to TPO and thyroglobulin
Term
describe subacute thyroiditis etiology and course
Definition
thyroid post-viral inflammation, usually hx of URI (granulomatous, lymphocytic, post-partum); 3 self-limited phases (hyper, hypo, eu) and hypo phase is transient, so life long rx unnecessary; cells are injured --> release preformed TH --> thyrotoxic (increased T4, normal T3, TSH suppressed) --> inflammation resolves --> mild hypothyroidism
Term
which drugs are assoc with hypothyroidism?
Definition
lithium, iodides, high iodine intake, amiodarone, propylthiouracil, methimazole, INFa or INFb
Term
what is JOD-BASEDOW phenomenon?
Definition
iodine deficient patient --> chronic elevation and overstimulation with TSH --> supply large amount of iodine --> thyroid overproduces --> hyperthyroidism or hyperthyroid crisis
Term
what kind of patients are at risk for chronic lymphocytic thyroiditis?
Definition
downs syndrome (50%) tx with thyroxine while young can help with growth and development
Term
what is the long term effect of hypothyroidism on the pituitary?
Definition
hypertrophy. may result in hyperprolactinemia and galactorrhea (can be mistaken for pituitary tumor)
Term
what is the etiology of thyroid hormone resistance syndrome?
Definition
rare, autosomal-dominant disorder caused by inherited mutations in thyroid hormone receptor (abolish ability of receptor to bind to TH)
Term
what expected levels of T3/T4 and TSH in TH receptor resistance syndrome?
Definition
high for both. high TSH because receptors on pituitary for neg FB are also resistant
Term
what are 2 things that can precipitate myxedema coma?
Definition
cold exposure, sepsis, other stressful situations
Term
what lab tests help distinguish myxedema coma from sick euthyroid syndrome?
Definition
SES = increased T3R, decreased cholesterol and decreased TSH; Myxedema = myxadematous appearance, low T3R, high cholesterol, high TSH
Term
tx for primary hypothyroidism?
Definition
replace/normalize thyroxine. pill once a day. for young people can normalize with higher dose pill right away. for older people, need to start low because too high of a dose could precipitate tachycardia
Term
how to treat secondary hypothyroidism?
Definition
replace thyroixine. replace adrenal steroids too if needed, bc increasing metabolism with thyroid hormone replacement can increase metabolism of adrenal hormones and pt may become suddenly hypoadrenal)
Term
what are the 3 features of graves disease
Definition
diffuse hyperplasia of thyroid and thyrotoxicosis; dermopathy; infiltrative ophthalmopathy
Term
what HLA haplotypes is graves associated with?
Definition
HLA B8 and HLA DR3
Term
what would we expect to see on nuclear imaging for graves disease?
Definition
symmetrical homogenous increased uptake of radionuclide
Term
describe the 3fold tx plan for graves
Definition
1. immediate decrease in thyroid hormone (PTU and methimazole inhibit TPO --> prevent oxidation of trapped iodine, prevent coupling of iodotyrosines, and PTU inhibits conversion of T4 to T3, no effect on preformed TH; Iodine blocks release of preformed TH) 2. decrease sx related to increased adrenergic tone (tachy, palpitations. use b blockers - propanolol prevents conversion of t4 to t3) 3. long term anti-thyroid (meds, radioactive ablation of gland, surgery)
Term
major AE of antithyroid meds?
Definition
agranulocytosis (go to ER if have fever or sore throat)
Term
how do we treat thyroid storm?
Definition
hydrate, antithyroid meds to stop synthesis, iodine to block release, glucocorticoids, avoid aspirin (dissoc thyroid hormone from binding globulin), tx underlying cause
Term
describe solitary toxic thyroid nodule
Definition
3cm nodules, overactive, produce T3/T4, low TSH, suppress remainder of gland. d/t activating mutation of TSH receptor?
Term
how do we treat solitary toxic thyroid nodule
Definition
no spontaneous resolution; use radioactive iodine (use antithyroid meds to pre-treat before RAI or surgery)
Term
describe toxic mulit-nodular goiter
Definition
at least 2 autonomously functioning nodules w/signs and sx of thyrotoxicosis (occasionally not); sometimes precipitated by pharm doses of iodine in ppl with underlying non-toxic multi-nodular goiters (common in areas of iodine deficiency)
Term
what would we expect to see on a nuclear scan of toxic multinodular goiter?
Definition
heterogenous areas of high and low uptake
Term
how do we treat toxic multinodular goiter?
Definition
antithyroid drugs to pre-tx before radioactive iodine tx; radio-ablation; surgery
Term
what is the tx for jod-basedow syndrome?
Definition
self-limiting once source of iodine stopped
Term
describe painful subacute thyroiditis (de quervains)?
Definition
viral origin, assoc with HLA B35; giant nucleated cells; fever, malaise, thyroidal pain extending down the ears or anterior chest wall (uni or bilateral), s/s of thyrotoxicosis, VERY tender thyroid, firm and irregular; mild hyperthyroidism (T4>T3 because d/t release of hormone, not synthesis)
Term
what does radio scan look like for de quervains?
Definition
low iodine uptake (reflects destructive nature of process)
Term
how do we tx de quervains?
Definition
aspirin or nsaid (4-8 wks), steroids if severe, b blockers if thyrotoxicosis is severe, may have transietn hypothyroidism; NO antithyroid drugs
Term
describe painless lymphocytic thyroiditis aka hashimotos hyperthyroid phase
Definition
s/s thyrotoxicosis, mildly enlarged thyroid, followed by hypothyroidism, ~50% dev long term hyperthyroidism, increased anti-TPO and anti-tg abs, assoc with other autoimmune diseases
Term
how do we tx painless lymphocytic thyroiditis?
Definition
b blockers for thyrotoxicosis, long term problems may require thyroxine replacement rx; NO antithyroid meds
Term
what are the 2 hyperthyroid problems assoc with pregnancy?
Definition
1. postpartum thyroiditis (hyper or hypo); 2. excess b-hcg from a molar pregnancy or choriocarcinoma (bhcg x-reacts with tsh bc of structural similarity --> pt becomes hyperthyroid with decreased TSH)
Term
how do we treat excess beta-hcg hyperthyroidism?
Definition
remove trophoblastic tissue
Term
what is thyrotoxicosis factitia
Definition
excess ingestion of thyroid hormone (usually t3)
Term
what is struma ovarii?
Definition
thyroid hormone production in the ovary (rare); thyroid nuclear scanning shows decreased uptake in the neck and increased uptake in the pelvic regions; tx by removing ovarian tumor
Term
what are parafollicular cells responsible for?
Definition
(C cells) synthesize and secrete calcitonin (inhibits bone resorption by osteoclasts)
Term
what does hashimotos look like histologically?
Definition
lymphocitic infiltrate, germinal centers, atrophic thyroid follicles, hurthle cells (metaplastic, eosinophilic)
Term
describe subacute thyroiditis symptoms?
Definition
sudden or gradual, neck pain esp with swallowing
Term
what does subacute thyroiditis look like grossly and histologically
Definition
grossly: enlarged, firm, yellow/white; histo: aggregations of lys, histiocytes and plasma cells, multinucleate giant cells enclose on pools of colloid (no germinal centers, no hurthle cells)
Term
what does graves look like grossly and histologically?
Definition
gross: symmetrical enlargement, hypertrophy, hyperplasia, soft and muscle-like; histo: papillae, scalloped edge of colloid, T cells, some germinal centers
Term
how do we tx graves
Definition
decrease sx of hyperthyroidism, reduce TH synthesis with drugs (or radiation, surg)
Term
describe (nontoxic) diffuse and multinodular goiters
Definition
impaired TH synthesis --> enlarged thyroid (usually d/t iodine deficiency). increase in glandular mass usually restores pt to euthyroid state. can be hypothyroid if compensatory increase in TSH is not adequte (congential defects in TH synthesis or inadequate access to iodine). can be hyperthyroid (if nodules hyperfunction --> toxic multinodular goiter)
Term
describe the gross and histo apperance of multinodular goiters
Definition
gross: exreme assymetric enlargement, compress trachea or esophagus. sometimes grows behind sternum/clavicles to produce plunging goiter. histo: well defined nodules lined by atrophied follicular epithelium (pushed back by abundant colloid) and no papillations
Term
what distinguishes follicular adenoma from carcinoma?
Definition
(both are unilateral painless mass, cold on scan) difference is that adenomas are well-encapsulated, whereas the carcinomas show capsular invasion (vs. papillary carcinomas can be solitary or multifocal, encapsulated or infiltrative)
Term
what is the major risk factor for follicular carcinoma?
Definition
exposure to ionizing radiation, particularly in first 2 decades of life
Term
most common type of thyroid cancer?
Definition
papillary carcinoma (then follicular)
Term
how do we distinguish follicular carcioma from papillary?
Definition
follicular nuclei lack the features of papillary carcioma (longitudinal nuclear grooves and "annie eye" nuclei)
Term
which carcinoma spreads vascularly? which spreads lymphatically?
Definition
follicular = vascular; papillary = lymph
Term
microscopic dx of papillary carcinoma?
Definition
finger-like papillae, orphan annie eye (optically clear nuclei), longitudinal grooves, psammoma bodies (laminated calcified structures = remains of necrotic papillae)
Term
3 important variants of papillary carcinoma
Definition
follicular (characteristic nuclei, follicular architecture); tall cell (no characteristic nuclei, tall columnar cells eosinophilic staining); microcarcinoma (typical, <1cm)
Term
whats the diff b/w MEN2a and MEN2b?
Definition
2a= medullary carcinoma of thyroid + pheochromocytoma; 2b= medullary carcinoma of thyroid and pheochromocytoma + mucocutaneous neuromas
Term
what do medullary carcinomas look like histologically
Definition
polygonal to spindle shaped cells (nests, trabeculae or folicles), amyloid deposits (from altered calcitonin molecules - look glassy pink and stain with congo red); membrane-bound electron-dense granules
Term
describe what sets anaplastic carcinomas apart from other thyroid carcinomas as far as presentation and prognosis
Definition
RAPIDLY enlarging bulky neck mass. 100% mortality. no tx, death in <1yr.
Term
what does anaplastic carcinoma look like histologically
Definition
highly anapalstic cells, large pleomorphic giant cells, spindle cells, sarcomatous appearance
Term
secondary hyperparathyroidism is almost always secondary to what?
Definition
depressed levels of serum calcium caused by renal failure
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