Pharm Final: Thyroid Hormones

Question 1

What is the function of the thyroid gland?

Answer 1

take iodine from food and convert to thyroid hormones thyroxine (T4) and triiodothyronine (T3)

these hormones regulate metabolism for almost every tissue in the body

Question 2

How much of each hormone does the thyroid gland produce?

Answer 2

80% T4, 20% T3

but T3 is four times as strong

Question 3

What happens if the thyroid hormones are low?

Answer 3

pituitary gland sends out TSH to make more hormones

Question 4

What is the most common form of hyperthyroidism?

Answer 4

Grave’s disease

Question 5

What is Grave’s disease?

Answer 5

autoimmune disease characterized by antibodies against TSH receptors, causing excess thyroid hormone

Question 6

What is most common form of hypothyroidism?

Answer 6

Hashimoto’s caused by destruction of thyroid gland

Question 7

What is common feature of Hashimoto’s?

Answer 7

iodine deficiency/excess, however rare in the US

Question 8

What drugs can cause hypothyroidism?

Answer 8

lithium carbonate and amiodarone

Question 9

What are signs of hypertyroidism?

Answer 9

heat intolerance, nervousness, insomnia, fast heart rate, weight loss, muscle weakness

TSH is low, Free T4 is high

Question 10

What is the goal of treatment for hyper?

Answer 10

treating sx with BB and using drugs that aim to decrease thyroid hormone synthesis

Question 11

When should pts be started on BB?

Answer 11

as soon as they are diagnosed with hyper assuming no contraindications

Question 12

What are the other three classes used to treat hyper?

Answer 12

thionamides = methimazole and propylthioracil

these are known as antithyroids as they block conversion of T4 to T3

Question 13

Which drug is prefered first line of tx in hyper?

Answer 13

Methimazole’s due to longer duration of action

also can be taken once daily, more rapid efficacy and lower incidence of AE

Question 14

Why is PTU used?

Answer 14

more in pregnancy as it will not cross placenta as much

Question 15

What is the time frame goal for thionamides?

Answer 15

attain euthyroid state within 3-8 weeks

this is followed by radio iodine or surgery or continuation of drugs for 1-2 years

Question 16

What is radioactive iodine used for?

Answer 16

complete destrcution of thyroid tissue, administered orally

simple and relatively safe lasting 6- 18 weeks

Question 17

What are general AE of thiomanides?

Answer 17

skin rash, itching may cause hypo

Question 18

What are signs and sx of hypo?

Answer 18

weight gain, cold intolerance, muscle cramps, memory loss

TSH is high, free T4 is low

goiter due to lack of dietary iodine

Question 19

What is drug goal for pts with hypo?

Answer 19

drugs that replace thyroid hormones that can contain either both T4 and T3 or just one or the other

Question 20

What is the preferred drug in replacement therapy?

Answer 20

synthetic tyrosine or levthyroxine (T4)

80% is absorbed and the half life is 7 days with once daily dosing

Question 21

Should levothyroxine be taken with food or on empty stomach?

Answer 21

empty stomach

Question 22

What are typical AE with levothyroxine?

Answer 22

subclinical hyper if too much given most common sign is Afib most likely in older pts, can be more hypo if not enough is given,

Question 23

Why else should elderly pts with CAD take be careful taking these?

Answer 23

thyroid hormone increasing myocardial oxygen demand which can be associated with arrhythmias, angina, MI

Question 24

What are PT implications of these meds?

Answer 24

hypo- CO can be affected leading to low exercise tolerance

hyper- have overstimulated cardiovascular system may have tachycardia and HTN