Thyroid and Anti Thyroid Drugs Flashcards
what are the thyroid hormones
T3 - Liothyronine (triiodothyronine)
T4 - Levothyroxine (thyroxine)
what are the thyroid hormones used for? (name them)
Liothyronine and Levothyroxine
Cretinism (thyroid hormone synthesis defect - kid hypothyroidism) adult hypothyroidism (myxedema)
AE of thyroid hormones
tremors, tachycardia, arrhythmias, heat intolerance
what are the different levels of hypothyroidism
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
features of hypothyroidism
weight gain, cold intolerance, bradycardia, constipation, poor memory, hoarse voice, Queen Anne’s sign
what is Queen Anne’s sign
thinning of hair in lateral third of eyebrows
presentation of cretinism
6 Ps Pot belly Pale Puffy faced child Protruding Umbilicus Protuberant tongue Poor brain development (mentally retarded)
causes of cretinism
lack of dietary iodine
defect in T4 synthesis
developmental failure of thyroid
some causes of hyperthyroidism
Grave's Toxic multinodular goiter Toxic adenoma Molar pregnancy Post partum thyrotoxicosis Post viral thyroiditis
presentation of hyperthyroidism
weight loss heat intolerance palpitation bowel frequency insomnia abnormal menses
drugs used for hyperthyroidism
BIT DIG
Beta blocker: propanol and esmolol
131-I
Thioamides: Propythiouracil and Methimazole
Diatriazote
Iodine and Iodine salts: Lugol solution and Potassium Iodide
Glucocorticoids
what are thioamides and what other names are they called and why
Propythiouracil (PTU) and Methimazole
AKA goitrogens because they can cause goiter
mechanism of thioamides (name them)
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
why do thioamides have a slow onset of action
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)
why is propythiouracil (PTU) preferred over methimazole during thyroid storms and in preggos
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
AE for thioamides (name them)
propythiouracil and methimazole
HHARV
Heptotoxicity Hypoprothrombinemia Agranulocytopenia Rash Vasculitis
AE seen with methimazole
Teratogenic – not used in pregnancy
Aplastic Cutis Congenita (absence of hair and epidermal layer of skin on head)
What are the iodine and iodine salts
Lugol solution
Potassium Iodide
mechanism of iodine and iodine salts (name them)
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
when does Wolff Chaikoff effect wear off? What happens after it wears off?
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
AE of iodine and iodine salts (name them)
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
mechanism of radioactive 131-I
taken up and sequestered in thyroid gland –> damages tissues by emitting toxic beta rays –> only damages thyroid tissue
AE of 131-I
hypothyroidism
contraindication of 131-I
pregnant women
nursing mothers
what are beta blockers used for in hyperthyroidism (name them)
propanolol (inhibits T4 to T3) and esmolol
control nervousness, palpitation, fatigue, weight loss, heat intolerance, and tremors
what can you give to patients who have asthma or COPD and cannot tolerate beta blockers
give them CCB Diltiazem or Verapamil
other than propythiouracil, what inhibits peripheral conversion of T4 to T3
PA-DIGS
Propanolol
Amiodarone
Diatrizoate
Iohexol
Glucocorticoids
Sodium Iodide IV
drugs that inhibits iodine concentration in thyroid gland by blocking its transportation
Perchlorate
Thiocyanate
Pertechnetate
what are some more anti thyroid drugs that can provoke autoimmune or destructive inflammatory thyroiditis hence leading to hypothyroidism
Amiodarone
Interleukin 2
Interferon alpha
Lithium
what is Grave’s disease
Ab that binds to TSH receptor and stimulates the release of thyroid hormones
only medical therapy that produces permanent reduction in thyroid activity
131-I
