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The thyroid gland secretes
T3=thyronine
T4=thyroxine
Calcitonin in parafollicular cells
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The thyroid gland is regulated by
TRH & TSH
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The thyroid gland is a
Vascular, two lobed, surrounds trachea
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The Hypothalamus secretes
TRH
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Once secreted by the Hypothalamus TRH goes to the
Anterior Pituitary
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Anterior Pituitary secretes
TSH
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Once the Anterior Pituitary secretes TSH, TSH goes to the
Thyroid gland
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Thyroid hormones have three principle actions
Stimulation of energy use
Stimulation of the heart
Promotion of growth and development
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Conditions of the thyroid
Hypothyroidism
Hyperthyroidism
Iodine deficiency
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Severe hypothyroidismin adults
myxedema/ slowing down of the body, gain weight, increased tolerance to cold, constipation
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Hyperthyroidism:
unexplained weight loss, always sweaty, hair can be thin, agitated and HR is always elevated, iodine (needed to create T3 and T4)
graves disease, exophthalamus (protrusion of the eyes) lidlag (above the iris there is white)
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Lid drop
crainial nerve is not working well
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TFT (Thyroid function test)
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Total T4 normal values
4.5-12.5 mcg/dL
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Free T4 normal values
0.9-2 ng/dL
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Total T3 normal values
80-220 ng/dL
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Free T3 normal values
230-620 pg/dL
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TSH normal values
0.3-6 microunits/mL
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Antithyroid agents
–propylthiouracil (PTU)
–methimazole (Tapazole)
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Thyroid Hormone Replacement
–levothyroxine (Synthroid)=synthetic T4
–Dessicated thyroid=bovine & porcine T4 +T3
–liothyronine (Cytomel, Triostat)=synthetic T3
–Liotrix (Euthroid)=synthetic T4+T3 in 4:1 fixed ratio
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Dessicated thyroid
no need to use this
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Synthetic T3 has a _______half life and is _____
short half life, expensive
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Liotrix:
fixed T3 and T4 (useless)
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Thyroid Agents
levothyroxine (Synthroid, Levothroid)
Other drugs in the class: liothyronine (Cytomel), liotrix (Thyrolar), Thyroid (Thyroid USP)
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Thyroid Agents Therapeutic Uses
Replacement therapy for hypothyroidism, treatment of goiter
Emergency treatment for myxedema coma
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Thyroid Agents Physiologic action
- Synthetic form of thyroxine (T4) that increases:
- metabolic rate,
- protein synthesis,
- cardiac output,
- renal perfusion,
- oxygen use,
- body temperature,
- blood volume
- growth processes
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Thyroid Agents Side Effects
Thyrotoxicosis: Hyperthyroidism manifestations
Allergic reactions-skin lesions, rash
Transient alopecia3
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Thyroid Agents Interactions
warfarin (Coumadin)
beta-blockers
digoxin
Insulin
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cardiac rhythm abnormalities with
catecholamines
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Drugs that accelerate levothyroxine metabolism
- Dilantin,
- Tegretol,
- rifampin,
- Zoloft,
- phenobarbitol
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Thyroid Agents Interactions:
Absorption decreased by
Calcium supplements
Antacids
Iron
Cholesterol binding agents
Food
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Cumatin interferes with
Blood clotting
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Beta blockers decrease the
affectiveness of synthroid
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Epinephrine and norepinephrine and dopamine are
catecholamines
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Dilantin is used for
seizures
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Thyroid Agents Nursing Implications
Monitor height and development in infants and children
Monitor for reversal of hypothyroid manifestations
Life long treatment controls symptoms, not a cure
Frequent follow up and lab monitoring
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Thyroid Agents Patient education
Optimal administration & course of therapy
Symptoms of hyper & hypothyroidism
Evaluate laboratory data for effective dose
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For Thyroid Agents what form is given to a pt in a coma
IV form
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Highly protein bound
thyroid-binding globulin
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propylthiouracil (PTU);
Other Drugs in the class
methimazole (Tapazole) -Longer half life
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Propylthiouracil (PTU) Therapeutic Uses
- Treatment for Hyperthyroid state and Graves’
- disease, adjunct treatment to irradiation, emergency treatment of thyrotoxicosis
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Propylthiouracil (PTU) Physiologic Action
Block the synthesis of thyroid hormones, prevent oxidation of iodide, block conversion of T4 into T3
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propylthiouracil (PTU) side effects
Agranulocytosis (>40 y.o., high doses, usually in first 2 months of treatment)
Hepatitis
Hypothyroidism
Nausea, arthalgia, headache, dizziness, paresthesias, liver injury
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propylthiouracil (PTU) Interactions
Opposes Vitamin K—enhanced anticoagulant effects
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propylthiouracil (PTU) Labs and Monitoring
Wt, Vital signs, T4 levels, CBC, LFT
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propylthiouracil (PTU) Half life
- Half-life 1-2 hours;
- Long time to onset of action—3-12 weeks
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propylthiouracil (PTU) caution
Pregnancy and Lactation , PTU safer than methimazole
Bc passes the placenta and a greater rate than tapizole
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Radioactive Iodine is Treatment for
- Graves Disease
- thyroid cancer and diagnostic procedures
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Radioactive Iodine Treatment for Graves’ Disease
Delayed hypothyroidism frequent complication
Contraindication
Pregnancy
Very young children, caution under the age of 30 yr
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A client tells a nurse that she has been taking levothyroxine (Synthroid) everyday for 9 days. She asks why there has been no improvement in her condition. The nurse’s best response is:
“It may take several weeks for you to notice a therapeutic effect from the drug”
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Propanolol (beta blocker) (Inderal) may be prescribed to clients with hyperthyroidism to
Decrease tachycardia and tremors
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For which of the following clients would radioactive
iodine (131 I) be contraindicated?
A client who is pregnant
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