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Pharm Test: Diabetes, Thyroid, Adrenal > Thyroid > Flashcards

Thyroid Flashcards

1
Q

What drugs block conversion of T4 to T3?

A

Beta-blockers
Steroids
Amiodarone

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2
Q

What three hormones are secreted by the thyroid?

A

T3: Triiodothyronine-9%
T4: Thyroxine-90%
Calcitonin

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3
Q

What makes up T3?

A

MIT + DIT

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4
Q

What makes up T4?

A

DIT + DIT

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5
Q

Which is more potent, T3 or T4?

A

T3 is 3x more potent

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6
Q

What chemical converts iodide to iodine?

A

Peroxidase

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7
Q

What chemicals can block iodide uptake into thyroid cells?

A
  1. Inorganic ions: thiocyanate and perchlorate
  2. Cardiac glycosides: by inhibiting K accumulation
  3. Bromine, fluorine, and lithium: block transport of iodide into thyroid
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8
Q

What is organification?

A

Peroxidase catalyzes iodination of tyrosine on thyroglobulin forming MIT and DIT

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9
Q

What drugs block organification and coupling of thyroid hormones?

A

Sulfonylureas

Thionamides

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10
Q

What chemicals can block proteolytic cleavage of thyroid hormones from thyroglobulin and thus their release?

A

High doses of iodide

Lithium

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11
Q

What chemicals are thyroid hormones transported on via plasma?

A

Thyroid binding globulin (TBG)
Albumin
Thyroid-binding Pre-albumin (TBPA)

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12
Q

At what TSH level should we treat?

A

> 10: L-thyroxine

<10: children; pregnant or infertile; symptomatic; thyroid autoantibodies

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13
Q

What are some negative effects of sub-clinical hypothyroidism?

A

Increased risk of coronary heart disease
Placental abruption risk
Preterm delivery risk
Women with thyroid autoantibodies at risk of abortion

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14
Q

Hypothyroidism effects on drugs?

A
  1. Digitalis: decreased volume of distribution
  2. Insulin: impaired degradation
  3. Warfarin: decreased breakdown of clotting factors
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15
Q

Causes of primary hypothyroidism?

A
  1. Hashimotos’s disease
  2. Iatrogenic: radioactive iodine, thyroidectomy
  3. Iodine deficiency: not common
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16
Q

What are some risk factors for hypothyroidism?

A

Post-partum women
Autoimmune endocrine disorders: DM type 1, adrenal insufficiency
Other conditions: celiac disease, vitiligo, MS, pernicious anemia, Down’s syndrome

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17
Q

What is myxedema?

A

Most severe form of hypothyroidism:

  • Appear to have edema beneath skin
  • Can cause coma
  • Hypothermia
  • Altered mental status
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18
Q

What are ADRs of Levothyroxine?

A
  • Arrhythmias
  • Tachycardia
  • Angina, sweating, weight loss
  • Restlessness, Osteoporosis
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19
Q

What drugs alter the absorption of levothyroxine?

A
  • Cholestyramine
  • Ferrous sulfate
  • Sucralfate
  • Aluminum hydroxide
  • Take thyroxine 2 hrs. before or 4 hours after
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20
Q

What drugs increase metabolism of levothyroxine?

A

Rifampin
Phenytoin
Carbamazepine

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21
Q

What effect do oral contraceptives/estrogen have on levothyroxine?

A

Increase binding to globulin reducing free thyroid

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22
Q

Indications for Liothyronine sodium?

A
  • Initial therapy for myxedema and myxedema coma
  • Short-term suppression of TSH before thyroid cancer surgery
  • Patients with 5’-deiodinase deficiency who cannot convert T4 to T3
23
Q

What is liotrix?

A

4: 1 Levo/Liothyronine

- Not more effective than Levo by itself

24
Q

How do we define subclinical hyperthyroidism?

A
  • TSH<0.1

- T4 normal

25
Q

What disease causes a diffuse toxic goiter?

A

Grave’s disease

26
Q

What are some causes of hyperthyroidism?

A
  • Grave’s disease
  • Painless thyroiditis
  • TSH-secreting adenoma
  • Human chorionic gonadotrophin-secreting tumor
27
Q

What is the most common cause of hyperthyroidism?

A

Grave’s disease:

  • Diffuse thyroid
  • Myxedema
  • Thyroid acropachy
  • IgG antibodies against TSH receptors
28
Q

In Grave’s disease is there more T3 released or T4 released?

A

T3

29
Q

Hyperthyroidism in pregnancy is almost caused by what?

A

Grave’s disease

30
Q

What is the drug of choice for hyperthyroidism in pregnancy?

A

PTU

31
Q

Treatment for hyperthyroidism during pregnancy?

A
  • Radiation of thyroid then supplement thyroid hormones

- PTU

32
Q

What drugs for hyperthyroidism are contraindicated in pregnancy?

A

RAI

Methimazole

33
Q

What characterizes a thyroid storm?

A

Severe thyrotoxicosis, high fever (over 103), tachycardia, tachypnea, dehydration, delirium-coma, N/V, diarrhea

34
Q

What is the treatment for thyroid storm?

A

Methimazole plus:
Anti-adrenergics
Corticosteroids

35
Q

What drugs are Thioamides?

A

PTU

Methimazole

36
Q

How do thioamides work?

A

Block thyroid hormone synthesis at substrates for iodination by thyroid peroxidase
-PTU also inhibits conversion of T4 to T3`

37
Q

What is drug of choice for hyperthyroidism for non-pregnant women?

A

RAI

38
Q

Which drug is more potent: PTU or Methimazole?

A

Methimazole is 10x more potent

39
Q

Most serious ADRs of Thioamides?

A
  1. Agranulocytosis-get baseline WBC count and stop if pt. gets fever or sore throat
  2. Hepatotoxicity-same as above
  3. Vasculitis-drug-induced lupus or antineutrophil
    - Can cause thyroid enlargement
40
Q

Most frequent ADRs with Thioamides?

A

Rash, arthralgia, cholestatic jaundice, lymphadenopathy, fever, psychosis, alopecia

41
Q

How do potassium iodines work?

A

Inhibition of TH secretion:

  • Blocks conversion of T4 to T3
  • Organification
  • Dilutes effects of iodine in blood and loads it in gland
  • Also blocks vascularity and size of gland
42
Q

Indications for iodines?

A
  • Pre-op for thyroidectomy (7-14 days)

- Used after RAI (3-7 days) to allow RAI to concentrate in gland

43
Q

Contraindications for iodines?

A

Do not use in breastfeeding women; can cause goiter in infants

44
Q

How do we administer iodines?

A

10-14 days before partial thyroidectomy w/ Methimazole or PTU; cannot give long-term because it will lose it effectiveness

45
Q

ADRs for iodines?

A

Hypersensitivity reaction

Lacrimation, conjunctivitis, laryngitis, thyrotoxicosis in patients w/ nontoxic goiter, drug fever, rash, metallic taste

46
Q

What are indications for radioiodine?

A

-Grave’s disease, toxic autonomic nodules, toxic multinodular goiters

47
Q

Major disadvantages of radioactive thyroid?

A
  • Hypothyroidism in most patients; usually women; can occur months or years after
  • African Americans more likely to be resistant to RAI-multiple doses
48
Q

MOA for lithium?

A

Inhibits incorporation of iodine into thyroid gland; inhibits release

49
Q

What do steroids help with?

A

-Thyroiditis or thyroid storm
Decrease thyroid function
Decrease immune response

50
Q

What drug causes the Wolff-Chaikoff effect?

A

Iodine

51
Q

What patients should not receive a thyroidectomy?

A

Patients w/ low RAI uptake

52
Q

What drugs should we give before a thyroidectomy?

A

PTU or Methimazole

53
Q

What are some complications for thyroidectomy?

A

Hyperthyroidism
Hypothyroidism
Hypoparathyroidism

Pharm Test: Diabetes, Thyroid, Adrenal (4 decks)

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