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pharmacology 2 > thyroid drugs > Flashcards

thyroid drugs Flashcards

1
Q

thyroid hormones

A

T3 and T4

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2
Q

T3

A

triiodothyronine

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3
Q

T4

A

thyroxine

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4
Q

controller of production of thyroid hormone

A

TSH

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5
Q

TSH causes

A
  1. increase blood flow to thyroid
  2. uptake of iodine into thyroid
  3. iodination of tyrosine in thyroglobulin
  4. formation of thyroglobulin associated T3 and T4
  5. release of stored T3 and T4

increases all steps

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6
Q

dietary form of iodine

A

iodide

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7
Q

movement of iodide

A

transported by high efficiency active transport into the cell
peroxidase strips off electron to make iodine into a radical
iodine binds tyrosine
3 iodines added to make T3 or 4 added to make T4

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8
Q

thyroglobulin

A

once properly iodinated is transported into the follicle and released under direction of TSH
taken up into vessicle where proteases cleave the protein and release the T3 and T4 amino acids and insert them into circulation

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9
Q

activity of thyroperoxidase

A

facilitates radicalisation and iodination and diodination

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10
Q

effects of thyroid hormones

A
  • growth and maturation
  • increased metabolic rate - increased uptake of amino acids and glucose, increased production of ATP
  • adrenergic facilitation
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10
Q

effects of thyroid hormones

A
  • growth and maturation
  • increased metabolic rate - increased uptake of amino acids and glucose, increased production of ATP
  • adrenergic facilitation
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11
Q

ligand for thyroid hormone receptor

A

T3

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12
Q

thyroid hormone receptor requires

A

retinoid x receptor

has to meet T3 together to become a transcription factor and enter the nucleus

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13
Q

TRE

A

thyroid hormone response element - the sequences of DNA recognised by the complex of thyroid hormone receptor and retinoid x receptor

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14
Q

hypothyroidism may be caused by

A
  • autoimmune thyroid disease
  • odine deficiency
  • surgical removal or radio-iodine treatment
  • drug induced (lithium, antithyroid drugs, amiodarone)
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15
Q

hyperthyroidism may be caused by

A
  • graves disease (TSH receptor antibodies)
  • thyroid adenoma
  • thyroid hypertrophy (iodine sufficiency after deficiency)
  • over production of TSH (rare)
16
Q

replacing T3

A

more rapidly effective, eliminated more rapidly
available as IV formulation, for rapid treatment or life threatening hypothyroidism
also available as oral

17
Q

replacing T4

A

longer half life

available oral formulation

18
Q

adverse effects of supplementing T3 and T4

A
  • sinus tachycardia and other arrhythmias
  • angna
  • restlessnesss
  • tremor
19
Q

hyperthyroidism

A
  • remove gland and replace T4
  • irradiate gland and replace T4
  • inhibit thyroperoxidaase
  • prevent peripheral deiodination of T4
  • interfere with sympathetic nervous system facilitating action of T3 and T4
20
Q

irradiate thyroid gland

A

taken orally as an iodide salt (radioactive form)
actively incorporated by thyroid epithelium
beta emission leads to death of thyroid tissue
half life of 8 days
patient ultimately becomes hypothyroid
then needs T4 replacement

21
Q

thiourylenes

A

carbimazole (a pro-drug for mathimazole) and methimazole
propylthiouracil

short half life, so dosed 2-4 times daily
slow onset of action, depletes follicle contents over 3 to 4 weeks

22
Q

adverse effects of thiourylenes

A

excessive suppression leads to hypothyroid
immunological, idiosyncratic
- marrow aplaasiaa or agranulocytosis
- skin rashes and other immune-mediated injuries
- severe liver toxicity with propulthiouracil

23
Q

potassium iodide

A

big doses
very rapid suppression of hyperthyroidism
onset at around 12 hours
control is quickly lost

24
Q

mechanism of potassium iodide

A

suppresses release of stored thyroid hormone

inhibits peripheral conversion of T4 to T3

25
Q

clinical use of potassium iodide

A

fast, temporary suppression of hyperthyroidism

  • life threatening hyperthyroidism
  • hyperthyroid patient facing emergency surgery
26
Q

monitoring T4 replacement and anti-thyroid drugs

A
  • TSH level more generally useful
    high TSH = needs more T4 or less antithyroid
    low TSH = needs less T4 ore more antithyroid
    free T4 measurement appropriate in some specific clinical situations
27
Q

high TSH

A

high TSH = needs more T4 or less antithyroid

low TSH = needs less T4

28
Q

low TSH

A

low TSH = needs less T4

29
Q

beta adrenergic blockaade

A

antagonises thyroid hormone facilitation of sympathetic activity
adjunct in managing hyperthyroid-related tachyarrhythmias
suppresses sympathetic manifestations - tachycardia, tremor, eyelid retraction

pharmacology 2 (19 decks)

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