Thyroid and Anti Thyroid Drugs

Question 1

what are the thyroid hormones

Answer 1

T3 - Liothyronine (triiodothyronine)

T4 - Levothyroxine (thyroxine)

Question 2

what are the thyroid hormones used for? (name them)

Answer 2

Liothyronine and Levothyroxine

Cretinism (thyroid hormone synthesis defect - kid hypothyroidism)
adult hypothyroidism (myxedema)

Question 3

AE of thyroid hormones

Answer 3

tremors, tachycardia, arrhythmias, heat intolerance

Question 4

what are the different levels of hypothyroidism

Answer 4

primary - due to thyroid itself not producing T3 or T4 as seen in Hashimoto’s thyroiditis –> anti TPO with Iodine deficiency

secondary - due to pituitary - low TSH

tertiary - due to hypothalamus - low TRH

Question 5

features of hypothyroidism

Answer 5

weight gain, cold intolerance, bradycardia, constipation, poor memory, hoarse voice, Queen Anne’s sign

Question 6

what is Queen Anne’s sign

Answer 6

thinning of hair in lateral third of eyebrows

Question 7

presentation of cretinism

Answer 7

6 Ps
Pot belly
Pale
Puffy faced child
Protruding Umbilicus
Protuberant tongue
Poor brain development (mentally retarded)

Question 8

causes of cretinism

Answer 8

lack of dietary iodine
defect in T4 synthesis
developmental failure of thyroid

Question 9

some causes of hyperthyroidism

Answer 9

Grave's
Toxic multinodular goiter
Toxic adenoma
Molar pregnancy
Post partum thyrotoxicosis
Post viral thyroiditis

Question 10

presentation of hyperthyroidism

Answer 10

weight loss
heat intolerance
palpitation
bowel frequency
insomnia
abnormal menses

Question 11

drugs used for hyperthyroidism

Answer 11

BIT DIG

Beta blocker: propanol and esmolol
131-I
Thioamides: Propythiouracil and Methimazole

Diatriazote
Iodine and Iodine salts: Lugol solution and Potassium Iodide
Glucocorticoids

Question 12

what are thioamides and what other names are they called and why

Answer 12

Propythiouracil (PTU) and Methimazole

AKA goitrogens because they can cause goiter

Question 13

mechanism of thioamides (name them)

Answer 13

Propythiouracil and Methimazole

block iodination of thyroglobulin and inhibit coupling reaction of DIT with MIT (to form T3) or with another DIT (to form T4) by inhibiting the enzyme used, TPO –> thyroperoxidase

Question 14

why do thioamides have a slow onset of action

Answer 14

they inhibit formation of newly formed T3 and T4 by inhibit TPO, thyroperoxidase

they don’t inhibit the preformed thyroid hormones so takes about 2-3 weeks to see full effect

propythiouracil does inhibit formation of T3 from T4 (but not methimazole)

Question 15

why is propythiouracil (PTU) preferred over methimazole during thyroid storms and in preggos

Answer 15

it also has inhibitory effect on 5-deiodinase so T4 cannot be turned to active T3

also less teratogenic so used in pregnancy

SN: most thyroid hormones released are T4 and need to be activated/deiodinated to T3 to be active

Question 16

AE for thioamides (name them)

Answer 16

propythiouracil and methimazole

HHARV

Heptotoxicity
Hypoprothrombinemia
Agranulocytopenia
Rash
Vasculitis

Question 17

AE seen with methimazole

Answer 17

Teratogenic – not used in pregnancy

Aplastic Cutis Congenita (absence of hair and epidermal layer of skin on head)

Question 18

What are the iodine and iodine salts

Answer 18

Lugol solution

Potassium Iodide

Question 19

mechanism of iodine and iodine salts (name them)

Answer 19

lugol solution and potassium iodide

large amount of iodine –> TPO thyroperoxidase inhibition –> inhibit thyroid hormone synthesis –> decrease organification and release —> Wolff Chaikoff Effect

also reduce size and vascularity of hyperplastic glands

Question 20

when does Wolff Chaikoff effect wear off? What happens after it wears off?

Answer 20

it wears off after 10-14 days –> Jod Basedow Effect which is hyperthyroidism after administering iodine –> goiter

hence Iodine and its salts are used short term

Question 21

AE of iodine and iodine salts (name them)

Answer 21

lugol solution and potassium iodide

CABE
Chronic Iodide intoxication
Anaphylactoid reaction - angioedema and swelling
Brassy taste and Burning of teeth and gums
Enlargement of parotid and maxillary glands

Question 22

mechanism of radioactive 131-I

Answer 22

taken up and sequestered in thyroid gland –> damages tissues by emitting toxic beta rays –> only damages thyroid tissue

Question 23

AE of 131-I

Answer 23

hypothyroidism

Question 24

contraindication of 131-I

Answer 24

pregnant women

nursing mothers

Question 25

what are beta blockers used for in hyperthyroidism (name them)

Answer 25

propanolol (inhibits T4 to T3) and esmolol

control nervousness, palpitation, fatigue, weight loss, heat intolerance, and tremors

Question 26

what can you give to patients who have asthma or COPD and cannot tolerate beta blockers

Answer 26

give them CCB Diltiazem or Verapamil

Question 27

other than propythiouracil, what inhibits peripheral conversion of T4 to T3

Answer 27

PA-DIGS

Propanolol
Amiodarone

Diatrizoate
Iohexol
Glucocorticoids
Sodium Iodide IV

Question 28

drugs that inhibits iodine concentration in thyroid gland by blocking its transportation

Answer 28

Perchlorate
Thiocyanate
Pertechnetate

Question 29

what are some more anti thyroid drugs that can provoke autoimmune or destructive inflammatory thyroiditis hence leading to hypothyroidism

Answer 29

Amiodarone
Interleukin 2
Interferon alpha
Lithium

Question 30

what is Grave’s disease

Answer 30

Ab that binds to TSH receptor and stimulates the release of thyroid hormones

Question 31

only medical therapy that produces permanent reduction in thyroid activity

Answer 31

131-I