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95 Cards in this Set

  • Front
  • Back
Thyroid function is regulated by what hormone?
TSH
describe the biofeedback loop for thyroid hormone production...
LOW THROID LEVELS stimulate the Hypothalamus to make TRH which act on the anterior pituitary to release TSH which acts on the thyroid to release T3 T4
T/F: a normally functioning thyroid system is an example of a negative feedback loop.
True
What is needed in the thyroid gland for t3t4 to be made?
iodine
most t3 is formed in the??
liver, kidney and muscle from deiodination of t4

little amount made in thyroid gland
T/F: most thyroid hormone travels in the blood in the free/unbound form?
FALSE. most is bound to protein, only small amount is free.
hypersecretion of thyroid hormone- t3t4 usually results in?
hyperthyroid and hypermetabolic state
Hyposecretion of thyroid hormone-t3t4 usually results in?
hypothyroid and hypometabolic state
list the physiologic effects of thyroid hormone
-affects fetal development, facilitates fetal growth
-promote basal metabolic function, regulates oxygen consumption and heat production
-affects CV muscle contraction
-stimulates bone resorption and formation
-permits normal glucose metabolism, absorption and storage
-synthesis and breakdown of lipids
-affects metabolism rate of hormones and drugs
what blood test is the best indicator of overall thyroid function?
TSH
What are the TSH levels for hyper, hypo and eu thyroid?
Hyperthyroid TSH<.3
Hypothyroid TSH>4
euthyroid TSH .3-4
small changes in the t3 and t4 can affect the TSH level in an_______________ relationship.
inverse
Which is kept at a more constant state and therefore correlates more with thyroid state-- the bound or unbound t4?
the unbound/free t4 level
Anti-TPO antibodies and antithyroglobulin antibodies are found in what patients?
-hashimotos
-graves
radionucleotide imaging
cannot be performed for at least 4 weeks after obtaining an iodine compound (IV contrast).
-may be falsely high in people who follow a high iodine diet
Thyroid scans
-assess the cause of the hyperthyroidism or the functional status of a nodule, they are NOT used to assess thyroid function.
-Iodine isotrope scan is preferred because it can distinguish hot from cold nodules.
*normal on scan, the isotropes are distributed evenly throughout the thyroid gland. Each lobe Is 3-4cm long and 1-1.5 cm wide….a mottled appearance is seen with hasimotos or in recently treated graves disease, an inhomogeneous uptake is seen in multinodular goiters
-hot, warm and cold nodules: hot are usually benign, cold nodules are usually benign as well BUT most malignant neoplasms appear cold
**normal RAIU (radioactive iodine uptake) is 30%
ultrasound
used to evaluate the anatomy of the thyroid gland and to differentiate solid from cystic nodules. Can be used to locate position and depth of lesion for fine needle aspiration. Also used to evaluate the cervical lymph nodes.
thyroid cancer on US usually is described as...
hypoechoic solid nodules
benign nodes appear
thin and oval with a echogenic hilium
malignant nodes appear
round with undefined hilium and may be vascular
MRI and CT are bed used to evaluate what?
to evaluate substernal goiters
PET scans are used for
has highest resolution for detection of aggressive metastatic thyroid cancer lesions, patient injected with radiolabeled glucose—cancer cells metabolize glucose quicker
a core biopsy specimen is attained through
FNA
define goiter
enlargement of the thyroid gland
causes of a goiter...
homone or immunologic stimulation, or from inflammatory, infiltrative or metabolic conditions (iodine deficiency, neoplasia, graves, thyroiditis)
What causes a simple goiter?
nontoxic: occur when thyroid gland enlarges in response to inadequate thyroid hormone
production.
how does lack of iodine cause a goiter?
results in the production of TRH which causes an increase in TSh--causing the retention by the thyroid of all available iodine in the body and causes an increase growth of the thyroid cells
What is the most common cause of non-toxic goiter in developed countries?
chronic autoimmune thyroiditis
on simple exam, non-toxic goiters are...
uniformly hypertrophic, hyperplasic, and hypervascular gland
What is the worry about non-toxic goiters?
-later fibrosis may lead to nodules
-if the nodules become autonomous then hyperthyroidism may occur, a condition known as toxic multinodular goiter
is the TSH elevated with non-toxic goiter?
-may or may not have elevated TSH, if TSH is not elevated the gland enlarges due to impaired hormone synthesis by increasing in mass and cellular activity, when TSH is high= gland enlarges from over stimulation
Describe the clinical presentation of someone presenting with diffuse or multinodular thyroid enlargement...
-difficulty swallowing and neck pressure
if undetected may grow downward to a substernal location
-symptoms from compression of the trachea, esophagus and vasculature
describe the physical exam on someone with a non-toxic goiter
-observe thyroid in good light (normal glad rarely visible)
-have patient extend the neck fully to permit inspection, also observe from the side to detect an enlargement between the cricoids cartilage and the suprasternal notch
**measure, a high likely hood that a goiter exists if proiminense >2mm
-have patient swallow water to enhance visualization
-palpate the gland and note the texture, small goiter= 1-2x larger, large= >2x normal size
what is pemberton's sign?
used is substernal goiter suspected
-have patient elevate both arms until the touch the side of the head, if the face flushed, cyanosis occurs or resp distress
-impingement of structures in thoracic outlet from goiter
diagnostics for non-toxic goiter
-low or normal free t4, and a high or normal TSH
-use US to look at size of thyroid and presence of nodules
-if necessary can perform FNA
what are the treatment indications for non-toxic goiter?
venous flow obstruction, compression of trachea or esophagus, progressive enlargement of entire goiter or nodules, neck discomfort
what are the treatment options for non-toxic goiter? which one is preferred?
-surgery: bilateral subtotal thyroidectomy—preferred treatment in the young and healthy, most then monitor TSH to see how much functioning thyroid is left and if treatment is needed
-levothyroxine will suppress TSH and correct any hypothyroidism and reduce the goiter size, best candidate= young with small goiter and high TSH
-radioactive iodine is useful in older patients and people with heart problems
what is a thyroid nodule?
-thyroid nodule=distinct lesion in the thyroid that is radioactively different from the rest of the thyroid
-thyroid nodules: include both solid nodules and cysts
what is a thyroid adenoma?
benign neoplastic tumors within a capsule
what causes thyroid nodules?
-causes: adenomas, cysts, carcinomas, mulitnodular goiters, hashimotos, thyroiditis
-less common causes: effects of prior surgery, parathyroid cyst or adenomas, thyroglossal cysts, lymphoma
T/F: thyroid nodules are usually asymptomatic and found on routine exam of thyroid.
TRUE
-also incidentally found on carotid doppler
what are the clinical factors that increase the likely hood of cancer?
head and neck irradiation, family history, younger than 20 or older than 60, male, history of endocrine neoplasia
name the manifestations of an anaplastic tumor.
enlarging painful mass with hoarseness, dysphonia, dysphagia or dyspnea, pathologic hip and spine fractures
T/F: patients with benign goiters will never be seen with compressive symptoms.
FALSE, patients with benign goiters may also present with compressive symptoms
name some diagnostic tests of thyroid nodules, and what is procedure of choice?
-must perform TFTs to r/o hyper or hypothyroidism
-elevated TSH associated with malignant transformation of thyroid nodule
-radionuclide scan: used as an initial test IF a hyperfunctioning nodule is suspected, useful In patients with multinodular goiter to target FNA of cold nodules
-US: should be performed for ALL patients with a suspected abnormality found on CT or MRI OR known thyroid nodules, able to distinguish between solid and cystic components
-US characteristics associated with increased likelihood for malignancy: increased vascular flow to the nodule, hypoechoic nodules, irregular margins, absent halo, microcalcifications, taller than wide
-FNA biopsy: PROCEDURE OF CHOICE in the evaluation of thyroid nodules, recommended for: nodule>5mm with high risk history, solid nodules>1cm that are hypoechoic, and complex nodules >1.5cm with any suspicious US findings
What test should be sent first when evaluating a thyroid nodule to determine the plan?
TSH level
in a patient with a thyroid nodule, if the TSH is normal, how do you manage the patient?
*if normal TSH and nodule on exam
-refer to specialist for FNA, US exam as well
-if benign, only repeat FNA if nodule is enlarging
-thyroid exam every 6-12mos
-task force recommends against the use of t4 suppression therapy
in a patient with a thyroid nodule, if the TSH is low, how do you manage the patient?
-if TSH suppressed, free t4 and TT3 should be obtained and a radioactive-iodine scan performed
-if the thyroid is hyperfunctioning (autonomously functioning adenoma)...need radioiodine or surgery….
-if the nodule is hypofunctioning--FNA biopsy
in a patient with a thyroid nodule, if the TSH is high, how do you manage the patient?
work up and manage hypothyroidism and if a single dominant nodule---FNA
If the FNA biopsy reveals CA, how do you treat?
-solitary ca lesion<1cm, lobectomy performed
-total thyroidectomy if history of neck and head irradiation, tumor extends beyond thyroid capsule, lesion >1cm
-task force recommends against the use of radioactive iodine ablation in patients with low grade ca (<1cm)
in bigger/ high risk: post op radioiodine therapy can be used to ablate the remaining tissue to make detection of reoccurrence easier
-patients with thyroid carcinoma: observed q3-6mos after d/x and surgery for 5 years then q6-12mos
-thyroglobulin and whole body scans are followed post-op.
-Patients are maintained on suppressive t4 to keep TSH between .2-.4
define hyperthyroidism
-excess production or release of thyroid hormone and its clinical manifestations
-hyperthyroid=thyroid is excess source of thyroid hormone
define thyrotoxicosis:
- syndrome produced by excess thyroid hormone regardless of source
-ex. over ingestion of iodine
primary hyperthyroid
independent of TSH
secondary hyperthyroid
dependent on TSH
-therefore TSH and t4 elevated
tertiary hyperthyroid
dependent on TRH
what is the most common cause of hyperthyroidism
**Graves disease= most common cause of hyperthyroidism, most common in women age 20-40
-thyroiditis= transient hyperthyroid and needs to be excluded
what is subacute thyroiditis?
post viral illness, thyroid is tender, multinucleated giant cells on micro, increased erythrocyte sed rate
-hyperthyroid first then hypothyroid
what is silent thyroiditis?
painless, autoimmune, lymphocytic infiltration on micro
S/S of hyperthyroid
-dry eyes, blurred vision
-diffuse goiter, can have thyroid brutis
-SOB with labored respirations
-palpitations, tachycardia, angina, HTN , CHF, a fib
-hyperphagia, hyperdefecation, weight loss, anorexia
-amenorrhea, infertility
-muscle weakness, heat intolerance, tremor, hyperreflexia
-pruritis, hyperhidrosis, warm moist palms, oncholysis, smooth velvety skin
-osteoporosis
-anxiety, irritable, nervous, insomnia
older adults: anorexia, constipation, normal pulse, weight loss
-NO SPECS: eye changes with graves disease no signs or symptoms, only signs no symptoms, soft tissue swelling, proptosis, extraocular muscle paresis, corneal involvement, slight loss optic nerve involvement
what causes the s/s of hyperthyroid
-symptoms due to increased sympathetic activity and increased catabolism
-apathetic hyperthyroidism: people who lack symptoms
what is the best screening test for primary hyperthyroidism?
TSH
--TSH will be low then a T3U and a T4 test should be performed
-TSH will remain suppressed for up to 3 mos after treatment, therefore free t4 must be monitored
-abnormal LFT are common
T/F: abnormal LFTs are common in people with hyperthyroidism.
TRUE
Results of radioactive iodine uptake and the different causes
-Decreased or zero radioiodine uptake: thyroiditis, iodine-induced hyperthyroid, exogenous cause of hyperthyroid, struma ovarii, metastatic thyroid cancer after thyroidectomy
-normal or high radioiodine uptake: graves, toxic goiter, toxic multinodular goiter, TSH induced hyperthyroidism, human chorionic gonadotropin induced hyperthyroid
what test is helpful to distinguish graves vs. thyroiditis?
radioactive iodine uptake
-increased with graves
-decreased with thyroiditis
lab results for graves, t3 toxicosis, t4 toxicosis and subclinical hyperthyroid
T3 T4 TSH
Graves Increase Increase Decrease
T3 toxicosis Increase Normal Decrease
T4 toxicosis Normal Increase Decrease
Subclinical normal normal decrease
what medication can be used for symptom treatment for hyperthyroid?
- beta blockers to alleviate the alpha-adrenergic symptoms (tremor and tachycardia), can use propranolol—titrate to symptoms (caution: bronchospasm, pregnant, CHF)
for patients <20 yrs and pregnant women, what is the hyperthyroid treatment of choice?
use medical therapy as treatment of choice: thioamides (antithyroid drugs)= MMI and PTU. –inhibit thyroid hormone synthesis by blocking organification, PTU also inhibits the conversion of t4 to t3 (can cause liver failure). PTU in 1st trimester and MMI in 2nd and 3rd trimester.
-Thioamides= most effective in patients with graves and small glands, used for 6-12mos
what is the treatment of choice in people >20 years old with hyperthyroid, and also treatment of choice in those who fail thioamide therapy?
-Radioiodine therapy= treatment of choice in those >20years and if thioamide therapy fails (not for pregnant women or graves with opthalamopathy), high incidence of post treatment hypothyroid monitor T4 at 4-6weeks after treatment and then monthly for 3-4mos.
when should surgery be used to treat hyperthyroid?
-surgery is for pregnant women who don’t tolerate thioamides, for patients who refuse radioiodine, and for people with obstructive goiter, complications: hypothyroid, hoarseness and hypoparathyroid
what are the side effects of thioamide therapy?
-agranulocytosis, MUST check CBC before treatment
-rash, arthralgia, myalgia and fever
-transient PTU liver injury, monitor LFTs
-nephrotic syndrome
-aplastic anemia and thrombocytopenia
-PTU not first line because of liver failure risk
Patient ed: D/C med for s/sx of infection: fever, sore throat. Get CBC
subclinical hyperthyroidism
-suppressed TSH with normal serum t4 and t3
-most are due to autonomously functioning thyroid nodules and mulitnodular goiters
-indications for therapy based on known skeletal and CV consequences from untreated hyperthyroid
-treatment should be considered with TSH<0.1
-with TSH .1-.5 with low risk, f/u monitor alone, if high risk (ex low bone density) consider treatment
sub acute thyroiditis treatment
symptomatic treatment with beta blocker during hyperthyroid phase, relief of pain with NSAID ASA or glucocorticoid, hyperthyroidism lasts for weeks-months and is then replaced with hypothyroidism, then returns to euthyroid
post partum thyroiditis treatment
symptomatic treatment with beta blockers when hyperthyroid, caution if breast feeding, thyroid hormone therapy during hypothyroid phase, tends to reoccur with subsequent pregnancies
what is the treatment of choice for toxic nodule and toxic multinodular goiter?
radioiodine ablation after beta blocker therapy
what are the consequences of untreated hyperthyroidism?
-untreated graves: afib, CHF, angina, osteoporosis
-thyroid storm: systemic decompensation, temp 102F, profuse sweating, HR 120+, afib, restless, confused, agitated, coma hospitalize
what are the typical diagnostic results in primary hyperthyroidism?
• TSH – Low (< 0.1)
• Repeat TSH – Low
• Free T4 – High
• T3 – High
• Thyroid stimulating immunoglobulin (high in Graves’)
• LFT’s - elevated
what is hypothyroidism?
-results from synthesis of thyroid hormone that is insufficient to meet the body needs
-most common disorder of the thyroid
what is primary hypothyroidism? what is the most common kind?
diseases or treatments destroy thyroid tissues, or prevalent conditions interfere with thyroid hormone synthesis, most common cause= chronic autoimmune thyroiditis
what is hashimoto's thyroiditis?
-if autoimmune thyroiditis is present with a goiter= hashimotos thyroiditis, autoimmune= body make autoantibodies against own thyroid antigens= destruction of thyroid tissue--increase in TSH, antithyroid antibodies (anti-TPO) and antithyroglobulin antibodies, then a drop in t3 and t4
what are the complications of untreated hypothyroidism?
-untreated hypothyroid: decreased metabolic function and na and fluid retention, impaired blood circulation and lymph drainage, skin thickening, renal and CV manifestation--myxedema
-thyroid hormone synthesis depends on dietary intake of iodides
who is at risk for hypothyroidism?
-people at risk: previous irradiation of the head and neck, radioactive iodine treatment for hyperthyroid, subtotal or total thyroidectomy
what is the pathophysiology behind hypothyroidism?
-thyroid hormone deficiency-- cardiac and metabolic consequences:
-impaired myocardial contraction, cardiomegaly, impaired lipid metabolism, atherosclerosis, HTN, fatigue, weight gain, altered kidney and GI performance: decreased GFR, low na, hypomotility, constipation, MS effects: increased volume of muscle and slowness of contraction, depression, anemia
*myxedema: interstitial edema of the heart muscle, striated muscle and skin
what is the clinical presentation accompanying hypothyroidism?
-subclinical hypothyroidism: asymptomatic TSH elevation
-overt myxedema: slowed mentation and visible symptoms
*most common presenting symptom is fatigue
-may be increased sensitivity to cold, weight gain, hoarsness, puffy face and hands, heavy and irregular period, brittle hair, depression, paresthesias, muscle aches and constipation
-goiter may or may not be present
-older adults: deaf, confusion, dementia, ataxia
what physical exam components should be included when evaluating someone for hypothyroidism?
-focus on general appearance and degree of energy
-note lethargy or slowness of mentation
-note texture, color and appearance of skin
-facial expression, hair texture and voice needs noted
-examine thyroid gland: may be small or large, if tender think subacute thyroiditis, if nontender think chronic autoimmune thyroiditis, if a rubbery firm symmetric goiter think hasimotos
-check reflexes, weight and VS
-HA or visual impairment may suggest secondary hypothyroid
what diagnostic exams are helpful in d/x'ing hypothyroidism?
-EKG: low voltage QRS, cardiac enlargement, bradycardia, slow respirations, decreased bowel sounds, slow mentation

Typical diagnostic results in primary hypothyroidism—increased TSH, decreased T4
• TSH - High (> 10)
• Repeat TSH - High
• Free T4 (Thyroxine) – Low
• Anti-thyroid Peroxidase Antibody (TPOAb) – High in Hashimoto’s
• Additional diagnostic testing required to rule out a pituitary or hypothalmic problem

-US can verify the presence of a nodule, and a FNA may be need to evaluate a suspicious nodule or rapidly enlarging goiter.
what is the drug of choice for treatment of hypothyroidism?
synthetic t4: levothyroxine
what are the treatment goals when using levothyroxine?
Goal: achieve euthyroid state (TSH 0.4 – 3.0 per AACE) and alleviate symptoms
-Synthetic Levothyroxine (T4) is the superior drug of choice
-euthyroid usually achieved 4-6 weeks after the onset of full dose therapy, daily dosage is then monitored 1-2 x a year to maintain a midnormal TSH level
what is the goal dose of levothyroxine used to achieve metabolic homeostasis?
1.6ug/kg/d
how should dosing of levothyroxine be initiated? in a healthy person <30-40 years with no medical problems? in the elderly?
-May start 50 mcg/day in healthy adults, goal is 100ug/day
-in healthy person can start at 100ug/day

-In elderly & patients with ischemic heart disease, start 12.5 to 25 mcg/day
-euthyroid is usually achieved in 4-6 weeks after onset of full dose therapy
what is subclinical hypothyroidism?
Abnormal labs without symptom…elevated TSH with normal thyroid hormone levels
what are the major causes of subclinical hypothyroidism?
-major causes: autoimmune thyroiditis and people with h/x of iodine ablation for hyperthyroid, also with inadequate t4 replacement in overt hypothyroid
when should subclinical hypothyroidism be treated?
-TSH 4.5-10: treatment may be considered if the patient has hypothyroid symptoms that could benefit from t4, monitor for subclinical hyperthyroid from medication

-TSH<10 without symptoms: monitor yearly
Caution: transient asymptomatic High TSH due to:
o Acute illness, severe stress, or trauma; some medications
o Daily fluctuation of TSH

• AACE recommends treatment of patients with any of the following:
o TSH > 10—treatment improves cardiac contractility, and lipids, and decreases atherosclerosis risk
o Positive Thyroid Peroxidase Ab (TPO)
o Goiter—treatment helps prevent growth and treat symptoms
-advise smoking cessation!
what is euthyroid sick syndrome?
-thyroid function abnormalities in a critically ill euthyroid individual
-hypothalamic suppression of TSH release, acute inability to peripherally convert t4 to t3, increased conversion of t4 to rt3low TSH, low t3, increased rt3
-seen during: carb restriction, liver disease, severe illness
-during recovery the TSH rises to normal or high—protective adaption to severe illness
what drugs can cause hypothyroidism?
-drugs may cause thyroid dysfunction or abnormal TFT
-amiodarone: iodine rich drug, highly lipophilic, concentrates in the thyroid with long halflife
-in chronic autoimmune thyroiditis: amiodarone causes hypothyroid, treat with levothyroxine replacement therapy
-in iodine deficient regions, amiodarone can lead to hyperthyroid
-interferon alfa: for treatment for hep B amd C, produced thyroid antibodies--hypothyroid
-lithium: blocks uptake of iodine--chronic autoimmue thyroiditis
what can happen to thyroid function with pregnancy?
-Hcg= weak thyroid stimulator, may cause hyperthyroid when pregnant
-TSH<.01 and high t4=hyperthyroid
-treatment goal: maintain t4 in high normal range
-hypothyroid can occur: treat!—need maternal euthyroid for fetal health: measure TSH 4-6 week after conception, 4-6week after any medication changes, and at least once each trimester