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Pharmacology > Thyroid > Flashcards

Thyroid Flashcards

1
Q

What is the primary function of the thyroid?

A

maintain/regulate metabolism in the body, helps children with growth and development, also temp regulation, wt, fat/CHO metabolism, HR, protein synthesis

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2
Q

3 glands involved in regulation of thyroid hormones?

A

hypothalamus, pituitary, thyroid

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3
Q

What is the normal TSH level

A

.4-4 mcg/mL

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4
Q

what is the normal T4free level?

A

.7-1.9 ng/mL

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5
Q

What is the key hormone when monitoring therapy?

A

TSH

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6
Q

What is the T1/2 of T4/T3?

A

T4- 7 days, T3- 1.5 days

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7
Q

What are the risk factors for thyroid disorders?

A

females 4x more likely, genetic predisposition

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8
Q

When to screen for thyroid disorders?

A

unexplained depression, cognitive dysfunction, hypercholesterolemia, sexual dysfunction, females>50

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9
Q

What is the hyperthyroidism prevalence?

A

1-2% of the population

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10
Q

What are the causes of hyperthyroidism

A

autoimmune (60-80%), thyroid ca, drug induced

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11
Q

What are sx of hyperthyroidism?

A

weakness, palpitations, increased sweating, tremor, nervousness, insomnia, distractibility, diarrhea, wt loss

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12
Q

What are physical findings of hyperthyroidism?

A

goiter, proptosis, blurred vision, thinning of hair, warm/moist skin, inc SBP, tachycardia, palmar erythema, high output heart failure

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13
Q

How is hyperthyroidism diagnosed?

A

increased free T4, TSH

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14
Q

What are treatment options of hyperthyroidism?

A

Thioamides, beta blocker, radioactive iodine, potassium iodine, thyroidectomy

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15
Q

Thioamides options

A

methimazole (Tapazole), propylthiouracil

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16
Q

MOA of thioamides

A

inhibit thyroid hormone synthesis by inhibiting peroxidase enzyme system of thyroid gland

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17
Q

How long do thioamides take for onset?

A

4-6 weeks, b/c does not impact the TH already available

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18
Q

What can thioamides be used for?

A

pregnancy, prior to surgery, graves’ disease

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19
Q

How does propylthiouracil work?

A

inhibits peripheral conversion of T4 to T3

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20
Q

What is the standard dosing for propylthiouracil?

A

50-150 mg TID until pt euthyroid then 50-200 mg TID for maintenance, has very short T1/2

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21
Q

How does methimazole work?

A

does not inhibit peripheral conversion, only works on the gland

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22
Q

Methimazole and propylthioruacil differences

A

M: preferred prior to surgery, PTU: preferred in pregnancy and lactation; M is 10x more potent than PTU, longer T1/2 QD

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23
Q

what is the standard dosing for methimazole

A

15-60 mg daily load, then 5-15 mg daily

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24
Q

How long is the treatment with thioamides?

A

1-2 years, then attemp tapering, 40-60% will fail off therapy, some require 5-10 therapy

25
Q

What are the ADRs of thioamides?

A

agranulocytosis, aplastic anemia, leukopenia, thrombocytopenia, GI upset, (take with meals!), hepatitis, rash, urticaria, pruritus

26
Q

How often should TSH and T4free be measured when on therapy?

A

4-8 weeks until at goal and then 3-4 months

27
Q

When are Bblockers used for hyperthyroidism?

A

adjunct only because of tachycardia, short term (4-6 weeks) until controlled

28
Q

What is the MOA of radioactive iodine?

A

ablates thyroid function without surgery, concentrates in thyroid gland and disrupt hormone synthesis, emits high energy B-particles that damages thyroid tissue

29
Q

What is radioactive iodine the treatment of choice for?

A

Graves’ disease

30
Q

How to give radioactive iodine?

A

dissolve in H2O of as a capsule, often successful after 1 dose, can repeat after 6 months

31
Q

What usually happens to pts after radioactive iodine therapy?

A

usually become hypothyroid and require supplemental TH therapy

32
Q

In what pts is radioactive therapy contraindicated?

A

pregnant pts

33
Q

How are pts monitored after radioactive therapy?

A

TSH and thyroid scan

34
Q

Potassium iodide MOA

A

block thyroid hormone synthesis and release, dec thyroxine synthesis, dec iodination of tyrosine and dec coupling of iodinated tyrosine residues, dec size and vascularity of thyroid gland

35
Q

When is potassium iodide used?

A

as preop treatment in Graves to incrrease gland firmness, in pts experiencing thyrotoxic crisis

36
Q

What are two forms of potassium iodide?

A

logol’s solution: 5% iodide, 10% KI, and SSKI

37
Q

What is the dose of lugol’s solution?

A

3-5 drops TID for 10 days prior to surgery, 1 mL TID for thyrotoxic crisis

38
Q

What is the dose of SSKI?

A

place drops in glass of water, juice or milk (1g/mL solution)

39
Q

ADR for potassium iodide?

A

unpleasant/metallic taste, burning sensation in mouth and throat, soreness of teeth and gums, GI upset

40
Q

When should thyroidectomy be performed?

A

in malignancy, large goiter, lack of remission w/ drug therapy, contraindication to drug therapy, usually use thionamides until euthyroid

41
Q

What decreases the size of thyroid gland (before surgery)?

A

preoperative iodides

42
Q

What is a thyroid storm?

A

life-threatening medical er with high mortality rate, tachy, hyperthermia, arrythmia, nausea, vomiting, diarrhea, delerium, coma

43
Q

What precipitates severe hyperthyroidism?

A

infection, surgery, trauma, radioactive iodine, or withdrawal from anti-thyroid meds

44
Q

How to treat thyroid storm?

A

treat precipitating cause, IV bblockers, iodide, PTU 300-400 mg PO TID and hydrocortisone 100 mg IV TID to combat hypoadrenalism

45
Q

What is the prevalence of hypothyroidism?

A

3-5%, increases w/ age, and F>M

46
Q

What are the causes of hypothyroidism?

A

presence of a goiter, autoimmune, Hashimoto’s disease, drugs (amiodarone, lithium, interferon-a), or absence of goiter- primary hypothyroidism, surgery/radiation, iodine deficiency, or secondary hypothyroidism

47
Q

What are symptoms of hypothyroidism?

A

fatigue, depression, cold intolerance, wt gain, dry skin, constipation, muscle aches, loss of taste, bradycardia, thin nails, arthralgias, goiter, thnning/yellow skin, lethargy, hair loss, HF

48
Q

How is hypothyroidism diagnosed?

A

elevated TSH>4.6, decreased free t4/T3

49
Q

What are the treatment options for hypothyroidism?

A

Levothyroxine, liothyronine (cytomel), also thyroid USP, thyroglobulin, liotrix, desiccated thyroid

50
Q

What is levothyroxine MOA?

A

synthetic T4, converted to T3

51
Q

Dosage and forms of levothyroxine?

A

25-300 mcg once daily, IV too, start lower dose in elderly- 25-50 mcg

52
Q

What is the education of levothyroxine?

A

take on empty stomach, 30-60 min before breakfast, take at same time each day, do not switch between brand

53
Q

What is monitoring of levothyroxine?

A

obtain TSH every 6 weeks at initiation until stable, obtain TSH every 6 weeks after each dosage, no sooner, titrate dose based on TSH level, once stable can obtain TSH every 6 months or if symptomatic

54
Q

What will increase TSH?

A

stress!!

55
Q

ADRs of levothyroxine?

A

symptoms of hyperthyroidism if excessive dose

56
Q

Drug interactions of levothyroxine?

A

cholestyramine, iron, fiber, antacid all decrease levels, CYP inducers increase the clearance

57
Q

MOA of liothyronine (Cytomel)

A

synthetic T3, shorter T1/2 than levothyroxine- more peaks and troughs which present similarly to hyperthyroidism, can use in adjunct to levothyroxine

58
Q

What is myxedema Coma?

A

advanced hypothyroidism with high mortality, acute decomposation of hypothyroidism, hypothermia, severe hypothyroid sx and coma

59
Q

How is myxedema coma treated?

A

IV levothyroxine and corticosteroids, improvements in 24 hours

Pharmacology (61 decks)

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