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ABBEY MSII Unit 5 > Pharm: thyroid and antithyroid drugs > Flashcards

Pharm: thyroid and antithyroid drugs Flashcards

(47 cards)

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1
Q

what is the precursor for thyroid hormone

A

tyrosine

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2
Q

T4

A

thyroxine

prohormone

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3
Q

T3

A

3,5,3 triiodothyronine

active hormone

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4
Q

reverse T3

A

3,3,5 triiodothyronine

inactive***

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5
Q

how is T4 converted to T3

A

type 1 (D1) and type 2 (D2) deiodinases

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6
Q

D1 expressed where

A

liver and kidney

~24% T4-T3 conversion

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7
Q

D2 expressed where

A

CNS, pituitary, thyroid, heart, adipose, skeletal muscle

~60% T4-T3 conversion

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8
Q

Type 3 (D3) deiodinase

A

predominantly expressed in the brain and skin in healthy adults
functions to INACTIVATE T3 - converts to T2 and reverse T3

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9
Q

how is iodide transported into thyroid

A

sodium-iodide symporter

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10
Q

what are the diseases caused by defective sodium-iodide symporter

A
  • symporter gene mutation (congenital hypothyroidism)

- autoimmune (Hasimoto’s) thyroiditis (autoantibodies against the symporter)

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11
Q

what enzyme leads to the synthesis of thyroid hormone from tyrosine

A

thyroid peroxidase (adds iodine and couples tyrosines)

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12
Q

what transports thyroid hormone to target cells in blood?

A

thyroxin-binding globulin (TBG)

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13
Q

how is thyroid hormone transported from colloid to blood?

A

endocytosed, fuse with lysosome, free thyroid hormone released

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14
Q

how is thyroid hormone transported into the target cells?

A
  1. simple diffusion
  2. MCT (monocarboxylate transporter family)
  3. OATP (organic anion transporting polypeptides)
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15
Q

where are MCT and OATP expressed? what are they important for?

A

expressed in liver, kidney, brain, heart

maintain intracellular concentrations of thyroid hormone

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16
Q

regulation of thyroid function (hypothalamus, anterior pituitary)

A

hypothalamus: TRH

anterior pituitary: TSH

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17
Q

TSH and T4 levels in: hyperthyroidism, hypothyroidism primary, hypothyroidism secondary

A

hyperthyroidism: TSH low and T4 high
hypothyroidism primary: TSH high and T4 low
hypothyroidism secondary: TSH low and T4 low

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18
Q

what does binding of T3 to thyroid hormone receptor lead to?

A

transcriptional regulation (activation or suppression) of thyroid hormone regulated genes

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19
Q

what hormone is released from the thyroid?

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A

80% T4 and 20% T3

20
Q

symptoms of hypothyroidism

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A

fatigue, depression, sensitivity to cold (lower metabolism), weight gain, goiter, muscle weakness, coarsening of the skin, dry or brittle hair, constipation, muscle cramps, increased risk of miscarriage

21
Q

hypothyroid diseases

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A
  1. hashiimoto’s thyroiditis: autoimmune antibodies against thyroid peroxidase or sodium-iodide symporter or TSH receptor
  2. iodine deficiency
  3. thyroid ablation
  4. secondary (central) hypothyroidism (pituitary or hypothalamus)
22
Q

myxedema

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A

severe form of hypothyroidism, mostly adult onset

23
Q

cretinism

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A

infancy/childhood hypothroidism. causes mental retardation and dwarfism

24
Q

treatment for hypothyroidism

Study These Flashcards
A

thyroid hormone replacement therapy

  1. levothyroxine sodium T4
  2. liothyronine sodium T3
  3. liotrix mixture of T4:T3
25
what is the preferred drug for use in the treatment of hypothyroidism? how is it administered?
``` levothyroxine sodium (T4) - longer half life and can be converted to T3 in peripheral tissues oral administration - IV or IM for people with GI diseases ```
26
which drug is for more acute scenarios of hypothyroidism
IV liothyronine - more rapidly effective (2-4 hr) | *it is also more potent than levothyroxine)
27
side effects of thyroid replacement drugs
dose related and more quickly occur with liothyronine - heart palpitations - nervousness - heat intolerance - excessive sweating - insomnia - tremor - frequent bowel movements - excessive weight loss
28
in which patients should thyroid hormone replacement be used with caution
``` angina, coronary artery disease, hypertension pregnant women (need adequate doses) ```
29
what is the most common preventable cause of mental handicap in the world?
iodine deficiency
30
iodine sources
soil and water
31
symptoms of hyperthyroidism
- rapid heart beat - weight loss - nervousness and alertness - heat intolerance - fatigue - increased bowel frequency - loss of sleep - tremors - excessive sweating - exophthalmus
32
grave's disease
MCC hyperthyroidism | autoimmune thyroid-stimulating antibodies causing overproduction of thyroid hormone
33
what are the causes of hyperthyroidism
1. graves disease 2. nodular goiter (most are benign) 3. thyroiditis 4. thyroid cancer
34
lab findings for hyperthyroidism
serum TSH decreased | T3 and free T4 elevated
35
hyperthyroid treatment strategies
1. subtotal thyroidectomy + replacement of T4 2. irradiate thyroid gland (radioactive iodine 131I) + replacement of T4 3. inhibit thyroid peroxidase activity with antithyroid drugs (propylthiouracil, methimazole, carbimazole) 4. interfere with thyroid hormone facilitation of sympathetic activite (beta blocker propranolol)
36
what are the antithyroid drugs
propylthiouracil, methimazole, carbimazole (prodrug of methimazole)
37
what is the mechanism of action of the antithyroid drugs propylthiouracil, methimazoke, carbimazole?
inhibits the organification of iodide and coupling of iodotyrosine causing inhibition of thyroid hormone synthesis (blocks thyroid peroxidase enzyme)
38
which antithyroid drug has additional activity and what is it?
propylthiouracil also reduces the deiodination of T4 to T3 by inhibiting D1 deiodinase activity
39
methimazole and propylthiouracil severe side effects
agranulocytosis, hepatitis, lupus-like syndrome
40
which antithyroid drug is safer with respect to agranulocytosis?
methimazole
41
which drug is the choice for pregnant women?
propylthiouracil
42
people developing one of the severe side effects from antithyroid drugs are then treated with what?
131I or surgery since agranulocytosis, hepetitis, and SLU Like syndrome are absolute contraindications
43
131 I
thyroid specific 131 I isotope is used to destroy sufficient thyroid tissue to restore euthyroid
44
what does 131 I emit
gamma rays and beta particles
45
how are patients with severe hyperthyroidism looking to use 131 I treated?
combination with antithyroid drugs or a beta blocker because effects are not seen for over 4 weeks
46
contraindications for radioiodine
pregnancy and breast feeding
47
mechanism for beta-adrenergic-antagonist drugs | which ones are used?
propranolol, metoprolol, atenolol, nadolol used as adjunctive agents in patients with graves' hyperthyroidism to control symptoms such as tremor, anxiety, palpitations

ABBEY MSII Unit 5 (8 decks)

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