PHARM: THYROID

Question 1

What is thyrotoxicosis?

Answer 1

any condition of excessive thyroid hormone and its effects.

so hyperthyroidism and thyroid storm.

Question 2

what can cause thyrotoxicosis?

Answer 2

Graves (hyperthyroidism)
toxic nodules
iodine excess
TSH-producing pituitary adenomas

Question 3

what is a common and likely adverse effect of thyroid surgery?

Answer 3

hypothyroidism

Question 4

what is radioactive iodine (iodine 131) used for?

Answer 4

used to ablate thyroid tissue with graves disease and toxic nodules.

Question 5

adverse effects of radioactive iodine?

Answer 5

high risk of hypothyroidism
possible worsening of graves orbitopathy
risk of radiation thyroiditis

Question 6

what drug decreases production of thyroid hormones and interferes with iodination and coupling of tyrosine?

Answer 6

methimazole

Question 7

adverse effects of Methimazole?

Answer 7

skin rash, allergic, agranulocytosis

hepatotoxicity (rare)

contraindicated in 1st trimester of pregnancy due to causing aplasia cutis

cannot affect thyroid storm or stored thyroid hormone.

Question 8

Propylthiouracil has a similar mechanism to methimazole. How does it differ?

Answer 8

additional action of inhibiting the conversion of T4 to T3 in periphery.

affects production of thyroid hormone and existing thyroid hormone

Question 9

adverse effects of Propylthiouracil is similar methimazole. How does it differ?

Answer 9

does not cause aplasia cutis

Question 10

which is preferred Propylthiouracil vs methimazole. When and why?

Answer 10

Methimazole due to lower risk of causing hepatoxicity and while patients are breastfeeding and in children.

Propylthiouracil is preferred during 1st trimester and it can be used to treat thyroid storm.

Question 11

Do beta blockers affect thyroid hormone production?

Answer 11

No

Question 12

What are Beta-blockers like Propranolol used for in thyroid conditions?

Answer 12

used to ameliorate the symptoms of adrenergic excess caused by excess thyroid hormones

Propranolol specifically can decrease conversion to T4 to T3 in periphery

Question 13

adverse effects of beta blockers?

Answer 13

bradycardia, dizziness, fatigue, headache, hypotension.

avoid in patients with asthma or conditions associated with bradycardia

Question 14

What is the standard treatment for hypothyroidism?

Answer 14

levothyroxine (oral T4)

replacement therapy

Question 15

How long does it take to attain a steady state after dosage adjustments of levothyroxine?

Answer 15

6 weeks

Question 16

what is the dosing of levothyroxine?

Answer 16

average adult: 1.6 mcg/kg/day PO

generally based on lean body mass

eldery patients need less

risk of angina: start with 12.5-25 mcg/day PO

Question 17

what does an initial dose of levothyroxine depend on?

Answer 17

endogenous thyroid function

Question 18

interactions that can affect absorption of levothyroxine?

Answer 18

may be reduced by antiacids and mineral supplementation
PPI and estrogens may interfere

anticoagulant drugs are variable

Question 19

How would you avoid possible interactions with levothyroxine?

Answer 19

separate administration by 6 hours, and usually taken in the morning

Question 20

adverse effects of levothyroxine?

Answer 20

hyperthyroidism if overtreated

possible exacerbation of angina

glycemic control may decline with initiation

Question 21

what does desiccated thyroid tablets provide?

Answer 21

T4 and T3 in fixed amounts.
comes in 30mg, 60mg, or 125mg.

Question 22

adverse effects of desiccated thyroid?

Answer 22

similar to levothyroixine

risks of CV and neurological adverse effects increase with larger doses due to T3

Question 23

what is conservative initial dose of levothyroxine?

Answer 23

25-50 mcg

Question 24

Patient returns for follow up 6 weeks after initial dose of levothyroxine and TSH value is unchanged. They take the medication every morning with an iron supplement. What is wrong?

Answer 24

Iron supplement, change time of supplement.