Thyroid

Question 1

Thyroid gland produces which two hormones?
Which hormone is more potent?
Which hormone has the shorter half life?
Which hormone is primarily formed by the breakdown of the other?
Which hormone is considered the active form?

Answer 1

T3 and T4
T3 is more potent
T3 has the shorter half life
T3 made from T4
Free T4 is considered the active form.

Question 2

Explain the release of thyroid hormones and the negative feedback loop.

Answer 2

The hypothalamus releases TRH which tells pituitary to release TSH which tells thyroid gland to make T4 and to a lesser extent T3. This also converts T4 –>T3 in the periphery.
Feedback mechanism: Elevations in T4 and T3 will inhibit secretion of TSH and creates a negative feedback loop.

Question 3

Explain what happens to the thyroid hormones in both hypo and hyperthyroidism?

Answer 3

Hypothyroidism: Low T4, High TSH
Hyperthyroidism: High T4, Low TSH

Question 4

What are the main signs and symptoms of hypothyroidism and what autoimmune condition is responsible for the most cases of hypothyroidism?

Answer 4

Cold intolerance, dry skin, weight gain, constipation, muscle cramps, voice changes, muscle pain, weakness, depression, bradycardia, coarseness of loss of hair.
Hashimotos disease where patients antibodies attack their own thyroid gland.

Question 5

What are the main signs and symptoms of hyperT and what autoimmune condition is responsible for the most cases?

Answer 5

Heat intolerance, weight loss (or gain), insomnia, tremor, thin hair, goiter, diarrhea, fatigue, agitation, tachycardia, palpitations
Graves disease:

Question 6

Which drugs can cause hypothyroidism?

Answer 6

Amiodarone, CBZ, eslicarbazepine, interferons, lithium, OXC, PHT, tyrosine kinase inhibitors (sunitinib)

Question 7

How frequently should TSH be monitored in hypothyroidism?

Answer 7

Q 4-6 weeks until normal, then 4-6 months, then yearly

Question 8

What is the generic and 2 brand names for synthetic T3.

Answer 8

Liothyronine (Cytomel and Triostat)

Question 9

Desiccated thyroid brand name and hormones contained?

Answer 9

T3 and T4. Armour Thyroid

Question 10

Levothyroxine should be taken in the AM at least 1 hour before breakfast or bedtime at least how many hours after last meal?

Answer 10

3 hours after last meal if taken at bedtime

Question 11

Starting dose for levothyroxine? What weight do we use?

What is the starting dose if the patient has known CAD?

Answer 11

1. 6 mcg/kg/day (IBW)

12. 5-25 mcg/day

Question 12

What main condition would warrant a decreased dose of levothyroxine?

Answer 12

Cardiovascular disease

Question 13

What is the IV:PO dose conversion for levothyroxine?

Answer 13

0.75:1

Question 14

What drugs can decrease levothyroxine absorption?

How far apart should you space these drugs?

Answer 14

Aluminum antacids, calcium, cholestyramine, iron, Mg, multivitamins, sevelamer, sucralfate, kayexelate, lanthanum
Space out by 4 hours.

Question 15

3 main options to treat hyperthyroidism?

Answer 15

Surgery, radioactive iodine, anti-thyroid medications

Question 16

What is the first line option for treating symptoms of hyperthyroidism?

Answer 16

Beta blocker to help with palpitations, tremors, tachycardia

Question 17

When initiated at high doses, How many months does it take to control symptoms with anti-thyroid medications?

Answer 17

It takes 1-3 months at higher doses to control symptoms, then the dose is usually reduced to prevent hypothyroidism

Question 18

What are the 2 generics/brands of the thionamides, what are they used for?

Answer 18

Polythiouracil (PTU)
Methimazole (Tapazole)
Indicated for hyperthyroidism

Question 19

BBW associated with PTU?

Answer 19

Severe liver injury and acute liver failure

Question 20

Which agent used to treat hyperthyroidism is preferred in 1st trimester? Which agent is preferred for 2/3 trimesters? Why?

Answer 20

PTU first
Methimazole during 2/3 trimesters
Increased risk of liver toxicity for PTU and fetal abnormalities for methimazole.

Question 21

Which are the 1 most common side effect with PTU and methimazole? What are 2 uncommon, rare, but serious side effects?

Answer 21

Common: GI upset
Serious: Hepatitis, agranulocytosis

Question 22

Which agent is preferred in thyroid storm? PTU or methimazole? Why?

Answer 22

PTU because it blocks synthesis of thyroid hormone

Question 23

What are the 2 generic iodides used in hyperthyroidism?

How do they work?

Answer 23

Potassium iodide and iodide solution (Lugols)
Saturated solution of potassium iodide (SSKI, Thyroshield)
They temporarily inhibit secretion of thyroid hormones, T4/T3 will be reduced for several weeks but effect will not be maintained

Question 24

What are the 9 signs or symptoms of thyroid storm?

Answer 24

Fever > 103
Tachycardia
Tachypnea
Dehydration
Profuse sweating
Agitation
Delirium
Psychosis
Coma

Question 25

What are the 5 mainstays of treating thyroid storm?

Answer 25

PTU
Beta Blocker
Inorganic iodide therapy
dexamethasone
Aggressive cooling with APAP and cooling blankets

Question 26

Which acronym can be used to help remember the colors of levothyroxine tablets?

Answer 26

Orangutans Will Vomit On You Right Before They Become Large Proud Giants
O=orange=25
W=white=50
V=violet=75
O=olive=88
Y=yellow=100
R=rose=112
B=brown=125
T=turqouise=137
B=blue=150
L=lilac=175
P=pink=200
G=green=300