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Week 51 > Thyroid > Flashcards

Thyroid Flashcards

1
Q

Drugs used in thyroid disease

A
  • Hypothyroidism
    • levothyroxine (T4)
    • Liothyronine (T3)
  • Hyperthyroidism
    • Thioamides (propythiouracil)
    • Iodide (Lugol solution)
    • Betal Blockers (Propanolol)
    • 131I
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2
Q

Clinical Presentation of Low TH

A
  • Cretinism-oral manifestations:
    • thick lips
    • macroglossia
    • malocclusion
    • delayed eruption of teeth
    • long term=impacted mandibular 2nd molars
  • Most common cause in the world= diet iodine deficiency
  • most common cause in the US=Hashimoto’s
  • Frequent signs:
    • dry, coarse skin
    • cool peripheral extremities
    • puffy face, hands and feet (myxedema)
    • diffuse aplopecia
    • bradycardia
    • peripheral edema
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3
Q

Pharmacological management: Low TH

A
  • TRH
    • diagnose TRH or TSH deficiencies, not in US
  • other agents inhibit TRH, but not alter TRH secretion.
    • Do not cause hypo or hyperthyroidism
      • bexaotene
      • dopamine
      • bromocriptine or cabergoline
      • Levodopa
      • corticosteroids
      • somatostatin
      • octreotide
      • metformin
      • interleukin-6
      • heroin
  • Levothyroxine
  • Liothyronine
  • Liotrix or desiccated thyroid=sometimes options
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4
Q

Levothyroxine

A
  • Low TH
  • synthetic T4
  • mechanism=TH(T4) agonist
  • first choice for thyroid replacement therapy
    • stable and uniform content
    • low cost
    • long half life (7 days)
    • converted to T3 intracellular so T3 administration is not necessary
  • Side effects:
    • children:
      • restlessness
      • insomnia
      • accelerated bone maturaiton and growth
    • Adults:
      • increased nervousness
      • heat intolerance
      • palpitations and tachycardia
      • unexplained weight loss
  • Impair Absorption:
    • Certain foods (Soy, bran, coffee)
    • drugs (oral bisphosphonates, PPIs, raloxifene)
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5
Q

Liothyronine

A
  • Low TH
  • synthetic T3
  • Mechanism=TH (T3) agonist
  • 3-4x more potent than levothyroxine
    • best choice for short-term TSH suppresion
  • Shorter half life (24hrs)
    • requires more doses
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6
Q

Liotrix

A
  • Low TH
  • Fixed dose combo of T3 and T4
  • Mechanism= TH(T3 & T4) Agonists
  • more expensive
  • Not more effective than liothyronine
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7
Q

Desiccated thyroid

A
  • Low TH
  • mammalian source
  • Mechanism=TH (T3 & T4) agonists
  • rarely justified
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8
Q

Low TH: Special Circumstances

A
  • Myxedema (severe hypothyroidism) and coronary artery disease
    • co-occur in older patients
    • low TH can protect heart against the increase demand
    • Myxedema corrections done with caution
  • Myxedema coma
    • results from untreated hypothyroidism
    • given IV loading dose of levothyroxine while in ICU
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9
Q

Clinical presentation of High TH

A
  • leads to:
    • increased risk of caries and perio
    • Goiter
      • affect lateral posterior tongue
    • maxillary or mandibular osteoporosis
    • Faster dental eruption
    • burning mouth syndrome
  • Increase Basal metabolism
  • Disrupted ANS
  • incidence higher in women (2%) than men (0.02%)
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10
Q

What are some conditions leading to high TH?

A
  • Diffuse toxic goiter or Graves disease
  • toxic nodular goiter
  • toxic adenoma
  • thyroiditis
  • follicular carcinoma
  • TSH-producing tumor of pituitary
  • Therapy-induced hyperthyroidism
    • xs T3 or T4 substitution
  • Xs iodine intake
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11
Q

Pharmacological management of high TH

A
  • Thiomides:
    • Methimazole
    • Propylthiouracil (PTU)
  • Anion inhibitors:
    • perchlorate
    • pertechnetate
    • thiocyanate
  • Radioactive iodine (131I)
  • Iodides:
    • Lugol’s solution
    • Potassium iodide
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12
Q

Thioamides

A
  • High TH
  • Include:
    • Methimazole
    • Propylthiouracil (PTU)
  • Mechanism: TH synthesis inhibitors
  • Both:
    • inhibit thyroid peroxidase-catalyzed rxns
    • block iodine organification and coupling of iodotyrosines
      • PTU also inhibits peripheral deiodination of T3 & T4 also
  • Methimazole
    • 10x more potent than PTU
    • drug of choice for adults and children
  • PTU
    • black box warning-severe liver toxicity
  • BOTH have short half lives, accumulation in thyroid=antithyroid action
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13
Q

Thioamides: Side effects

A
  • Nausea
  • GI distress
  • altered sense of taste or smell
    • in 3-12% for methimazole
  • Maculopapular pruritic rash
    • 4-5%
  • Rare side effects:
    • urticarial rash
    • acute arthralgia
    • agranulocytosis
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14
Q

Anion Inhibitors

A
  • High TH
  • Include:
    • perchlorate
    • pertechnetate
    • thiocyanate
  • Mechanism: TH synthesis inhibitors
    • different part of pathway than thioamides
  • All block uptake of iodide by thyroid
    • competitive inhibition of iodide transport mechanism
  • Main use
    • block thyroid reuptake of I- in patients with iodide-induced high TH
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15
Q

Radioactive Iodide (131I)

A
  • High TH
  • Only isotope used to tx Thyrotoxicosis
    • emits beta rays to destory thyroid parenchyma
  • Mechanism:
    • Thyroid Destruction
  • Contrainidicated in pregnant women
    • crosses placenta to destroy fetal thyroid
    • excreted in breast milk
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16
Q

Iodides

A
  • High TH
  • Include:
    • Lugol’s solution
    • potassium iodide
  • Mechanism:
    • TH synthesis inhibitors/release inhibitors
  • Were the major antithyroid agents before thioamides
  • inhibit organification and hormone release
    • decrease size and vascularity of thyroid
  • Usually used after start of thioamide therapy
    • if used alone-thyroid will escape iodide block in 2-8 weeks
      • withdrawal=severe exacerbation of thyrotoxicosis
  • Contraindicated in pregnant
    • cross placenta
    • induce fetal goiter
17
Q

Pregnant women with High TH

A
  • Both PTU and methimazole cross placenta and concentrated by fetal thyroid
  • PTU recommended
    • ONLY first trimester
      • black box warning-sever liver injury
    • bc it’s more tightly protein bound than methimazole
18
Q

Thyroid storm or thyrotoxic crisis

A
  • Suddent acute exacerbation of symptoms of thyrotoxicosis (High TH)
  • Beta blockers
    • propanolol or esmolol
    • control cardio manifestations
    • Propanolol also inhibits peripheral conversion of T4 to T3
  • Potassium iodide
    • ​slow release of TH from thyroid
  • Methimazole
    • ​blocks TH synthesis
  • Glucocorticoids
    • ​protect against ashock
    • block peripheral conversion of T4 to T3
19
Q

Throditis

A
  • Viral infection
  • destruction of parenchyma can lead to thyrotoxicosis
    • release of stored hormones
    • similar to hasimotos
  • Tx:
    • Propanolol or metoprolol
      • for tachycardia
    • Supportive therapy un resolution
      • recommened tx
20
Q

Graves Disease

A
  • Autoimmune disorder
    • antibodies against thyroid antigens
    • elevated free T3 and T4
    • suppressed TSH
  • TX:
    • thioamides or radioactive iodine(preffered tx in pts over 21)
    • Propranolol or metroprolol
      • tachycardia or cardiovascualr disease

Week 51 (8 decks)

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