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102 Cards in this Set

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What is the functional unit of the thyroid

Follicle wall

What is thyroglobulin?

Glycoprotein containing over 100 Tyr residues


Where TH is synthesized and stored

The thyroid is regulated by ___

1) HPT axis


-TH and ACTH provide negative feedback


2) TSH


-regulates and controls synth and release of TH from follicles


-multiple effects on TH, other hormones, thyroid gland, other tissue

How is TH synthesized

synth stim by TSH


1) I transferred into gland from blood via transporters RLS


2)TGn expression INC


3) I and TGn secreted into colloid


-I oxidized to I+ or converted to I2 by thyroperoxidase as ar the 2 Tyr residues of TGn (MIT and DIT)


4) Tyr's are coupled in colloid(synthesis)


-t3


-t4


-TGn+t4+t3 "droplets" (storage)

How is TH secreted?

Endocytosis of TGn droplets containing T3 and T4


Enzymatic TGn cleavage releases T4


T4 released into the blood

What are TH actions

1)Regulates overall metabolic activity and energy expenditure


-receptors on nucleus, mitochondria,membranes


Brain is exception


2)Growth and development(very important for FETUS GROWTH and DEVELOPMENT)


3)Inc activity of adrenergic nervous sys


4)Inc GI motility


5)Inhibit TRF, TSH (- feedback)

In what ways does TH regulate metabolic activity and energy expenditure?

1) inc basal metabolic rate


2)inc protein synth and catabolism


3) inc carbohydrate metabolism


Inc glycogen,gluconeogen


Inc gi absorp, adipose & muscle uptake of glucose


dec insulin action


Hyperthyroidism exacerbates DM


4) increases lipid and cholesterol metabolism


-inc lipolysis


-inc conversion of cholest to bile acids


Due to inc LDL rec on hepatocytes


Why hypothyroid have inc cholesterol

4 main ways

How does th inc adrenergic NS activity

Inc beta rec on heart skel musc adipose and lymphocytes


Dec alpha rec in myocardial tissue


Inx catechol sensitivity


+inotropic +chronotropic

4 ways

Hypothyroidism (Or Gull's Disease) is more common on ___

Older women ( 4-8x more likely in women)

Gull's disease is a ___ onset that tends to ____

Slow


"Wax and wane"

Typical signs and symptoms of hypothyroidism are:

-chronic fatigue,somnolence, expressionlessness


-poor circulation


-muscle cramps (dec muscle func)


-faulty hearing


-unexplained weight gain


-decreased mental func and motor activity


-cold, dry skin, hair loss


-Hothermia/cold sensitivity


-constipation


-reproductive disorders


- cardiac difficulties (dec CO, bradycardia, dec BP)


-goiter (usually diffuse non toxic goiter)


-myxedema

What is myxedema

Severe hypothyroidism in which poor lymph drainage leads to SubQ buildup of mucopolysaccharides characterized by:


-puffy hands and feet


-swelling of cheeks and tongue


-Puffy eyes and droopy eyelids


- dec CV function, CO and glomerular filtration


-NOT correctible with diuretics

What are lab values associated with hypothyroidism

Hypercholesterolemia


dec drug metab and elimination (higher drug half life)


TSH levels

Types of PRIMARY hypothyroidism

Hashimoto's thyroiditis (90%)


Thyroidectomy of radioactive I tx


Endemic(area w low I)


Drug induced


Cretinism


Myxedemic coma

What is hashimotos thyroiditis

Chronic autoimmune thyroiditis- autoantibodies attack thyroid causing damage and inflammation


Most people have it


Mean age diagnosis ~60

What drugs can induce Hypothyroidism

Amiodarone


Iodine


Lithium(5-15% in long term tx)

What drugs cause both hypo and hyperthyroidism

Amiodarone and Lithium

What is cretinism

Congenital hypothyroidism that can lead to irreversible mental and growth retardation

What are signs and symptoms of cretinism

Thick tongue


Dry,brittle hair


Hypothermia: dry, cool skin


Poor feeding


Choking episodes


Short extremities


Goiter


Overall inactive/ sluggish

What is a myxedemic coma

Medical emergency with a 60% mortality rate and is associated with severe and chronic hypothyroidism

What are clinical features of myxedemic coma

Profound hypothermia


Unconsciousness


delayed reflexes


Respiratory depression


Bradycardia


Rough skin

What are precipitating factors of myxedemic coma

Stress


Infection


Hypothermia

What are possible treatment options for myxedemic coma

Liothyronine sodium (T3) injection


-triostat, cytomel

What is a treatment option for endemic hypothyroidism

Iodine

What are different TH replacement agents

Levothyroxine (pure T4)


Liothyronine sodium (T3)


Thyroid USP (dessicated thyroid) (4/1 ratio 4/3)


Liotrix (older)


Thyroid strong (older) natural prep 1.5 more potent than thyroid USP

Levothyroxine has a ___ t1/2 and is ____ absorbed.

Long


Well (50-70%)

Brand interchange with levothyroxine is ___

Not recommended due to formulation differences

Levo should be taken when the stomach is ___

Empty

Levothyroxine drug interactions

Fe


Ca


Al


sucralfate, cholestyramine

What is the equivalent dose of levo

100 ug

Liothryonine sodium has a ___ onset ___ duration and is ___ potent than T4

Rapid


Shorter


More

What is the equivalent dose for triostat

25-30ug

What is the equivalent dose of thyroid USP

About 65 mg (1 grain)

Hyperthyroidism (grave's disease) is ___ and is typically seen in ____

Not as common as hypo


Young adults

What are some signs and symptoms of hyperthyroidism

Exaggerated TH effects


-elevated BMR


-warm,nervous


-weight loss


-increased appetite


-muscle weakness and hyperreflexia



Osteoporosis


Inc RBC mass: inc menstrual flow


Arrhythmias (tachycardia)


Exopthalamus


1) TSH induced inflamm of connective tissue


2) ai reaction leads abies mimicking TSH wh activate TR leading to deposits in eye socket


3) eyelid retraction/ lag


Goiter

Types of primary hyperthyroidism

1)Graves disease (diffuse toxic goiter, exopthalmic goiter)


2)Nodular toxic goiter


3)drug induced

What is graves disease

AI disorder that is the predominant cause of hyperthyroidism in which ANTIBODIES mimick TSH and overstimulate gland with no negative feedback loop

What are characteristics of graves disease

Diffuse toxic goiter (entire gland enlarges and hypertrophies, high th leads to thyrotoxicosis)


Exopthalmos


Pretibia myxedema(thyroid dermapothy)


Can "wax and wane"

What is a nodular toxic goiter

Isolated nodes or groups of cells in the thyroid gland that become hyperactive and resistant to pit feedback regulation



Not the whole gland

Generally do NOT observe ___ with nodular toxic goiter

Exopthalmos

A diffuse non toxic goiter is thought to be caused by

Increased TSH due to higher T3 levels caused by I defecit?

Endemic goiters are caused by __ leading to ___ TH levels and ___ TSH levels

I deficiency


Decreased


Increased

Treatment for a nodular toxic goiter is

Surgery

Treatment for a diffuse non toxic goiter is

Iodine

Treatment for a diffuse toxic goiter is

Surgery


Radioactivd I


Drugs

Treatment for an endemic goiter is ___

Iodine

What drugs can induce hyperthyroidism

Amiodarone


Lithium

__ is essential for first trimester growth and development

TH

Hyperthyroidism in pregnancy is usually caused by __

Graves disease

Thyrotoxicosis (excessive th levels) in pregnancy can cause

Cv complications


Preeclampsia


Premature birth/ miscarriage


Low birth weight


Thyroid storm

What agents are available to treat hyperthyroidism

Antithyroid agents


Thioamides


Iodines


Radioactive iodine


Surgery


Beta blockers (propranolol)

Antithyroid agents are more successful in ____

Mild diffuse toxic goiter

Antithyroid agents are useful for ___

Young Adults and children

If using antithyroid agents in pregnancy___ because ____

Use lower doses


Higher doses may induce hypothyroidism in fetus

Constant use and correct dosage are paramount with __ Bec d/ of therapy after one year results in relapse of up to ___% of patients

Antithyroid agents


50

What is the MOA of thioamides

Inhibition of thyroperoxidase


PTU- inhibits monodeiodination of T4

What are the 2 thioamide agents in use today

Methimazole (MTZ)


Propylthiouracil (PTU)

What are advantages of using thioamides

Causes no permanent damage


Concentrates in thyroid


Any hypo is reversible by lowering dose


Refractiveness uncommon


SE low- fever and rash

Disadvantages of using thioamides (MTZ and PTU)

1-2 mth for effect (need to deplete t3/t4 stores)


May cause goiter b/c of inc TSH due to depletion of stores


Therapy is long and must be continual


Not a cure and may not work with severe disease


Pregnancy category D(mtz)


Short T1/2 (PTU)

What is a serious side effect of thioamides

Agranulocytosis


PTU dose related?


Look for fever, rapid developing sore throat


Rapid onset

PTU is the DOC in___

1st trimester, thyroid storm

MTZ is DOC in all situations but __

1st trimester and thyroid storm

The effects of iodides on hyperthyroidism wear of in about___

2 months

At pharmacologic doses, iodides ___

Dec t4/3 synthesis and secretion


Reduce vascularity of the thyroid gland

Iodides are used for__

Surgery prep


Diffuse non toxic goiter


Radiation emergency (nuclear stuff to prevent cancer)

What is the mechanism for radioactive I (RAI)

I131 concentrates in the thyroid

Pros of using RAI

Destroys thyroid tissue


Simple convenient and permanent


Works well for small nodular or diffuse toxic goiters


Usually 2nd or 3rd line

Cons of using RAI

3-4 weeks for onset and 4 mths to full effect


Can be too effective and too permanent (cause HoThyroid)


Crosses placenta and damages fetus so CI in pregnancy


Occasional damage to parathyroids

RAI is used in

ADULTS 30- 40


And refractory pts or pts hypersens to drugs

Surgery for hyperthyroidism is __

Useful for large nodular toxic goiters and always for malignancies


Used in drug sensitivity or failure


Only used in pregnancy if necessary


All disadvant of surgery


Occasional PTH damage


VERY effective

What is thyroid storm

Life threatening, exaggerated thyrotoxic manifestations usually seen in untreated, severe hypothyroidism

Symptoms of thyroid storm include:

Agitation


Confusion


Diarrhea


Restlessness, shaking


Severe hyperthermia


Sweating


Tachycardia

What concurrent medical conditions can precipitate thyroid storm

Infection


CV distress


Stress

Treatment of thyroid storm includes high doses of:

Beta blockers


Anti arrhythmics


Antithyroid agents (PTU and iodides)


Ice bath, ice packs, acetaminophen

Primary thyroid disease originates in___

Thyroid

Allison

Secondary disease is caused by ___

TSH from pituitary

jA

Tertiary disease is caused by___

TRH from hypothalamus

Ja

Resin T3 uptake is

An indirect measurement of the degree of saturation of thyroid binding globulin (TBG)


It gives an INDIRECT estimate of free t4 avail for binding to TBG

FT4 I = ____

RT3U x TT4

FT4 I compensates for ___ and is ___ expensive than measuring FT4

TBG


Less

Normal TSH range is

0.4 - 2.5 uU/mL

TSH is ___ in primary hypothyroidism

Elevated

Iatrogenic hypothyroidism is ___

Caused by healthcare sys somehow


Rai, surg, DI

Drug induced hypothyroidism caused by

Nitroprusside


Amiodarone


Lithium


Sulfonylureas(esp 1st gen)

Ja

A TaRGET DOSE for levo can be set as:

1.6 ug/kg/d

A senior citizen (>60) or anyone with a + h/o heart disease should be started on a much ___ dose because___

Lower


Target dose could unmask a pre existing heart condition and precipitate angina

A senior citizen starting levo should be monitored for__

HoThyroid symptoms


TSH


Chest pain

Doses of levo should be readjusted every 6-8 weeks toward target dose with an end goal of ___

Normal tsh levels

TSH is __ in secondary hypothyroidism

Low

What kind of effect does dessicated thyroid have on thyroid tests

normal FT4/FT4I


TSH normal or


Inc TT3

Couples having trouble conceiving should have ___ levels tested

TSH

Hyperthyroidism etiology:


____ is autoimmune


____ toxic nodules


____ viral - also self limiting


____

Graves disease


Plummer's disease


Sub Acute Thyroiditis


Drug induced

Monitoring for thioamides should include___

CBC with differential

_ is NOT an absolute CI for thioamides but _ is

Rash


Agranulocytosis

_ provide symptomatic relief before onset of thioamides use in thyroid storm and as a preop adjunct.

Iodides

DONT USE _ before RAI

Iodides

Adrenergic agents in hyperthyroidism ___

Block the peripheral action of TH but have no effect on disease state.

When it comes to adrenergic antagonists, ___ are preferred agents

Beta blockers (propranolol)

Use__ in hyperthyroidism during pregnancy or lactation

PTU and BB

Steroids like prednisone can be used to prevent worsening of ___

Exopthalmos

AFib with hyperthyroidism should be treated with additional meds like

Beta blockers


CCBs


Digoxin

Thyroid storm treatment :

Support with sedation


O2


Fluids


Thioamides


Lugols solution30-60 gtt/d


Bb (propranolol)


CCB (diltiazem)