Thyroid Disorders

Question 1

Levothyroxine

Answer 1

IND: Hypothyroidism, post-partum thyroiditis, myxedema coma, TSH suppression in certain thyroid cancers. Most used.
MOA: Synthetic T4
BOX: Not for weight loss. Larger doses that can elicit weight loss also produce life threatening rxns
CON: Uncorrected adrenal insufficiency
ADR: In excessive doses, s/s of hyperthyroidism can occur = level check and possible dose reduction
Peak therapeutic effect not seen for 4-6 weeks

Question 2

Levothyroxine Dosing and Management

Answer 2

Take first thing in the am, 30 min before food or at night 3-4 hrs after a meal. Don’t administer within 3-4 hours of iron or calcium contrast
Drug interactions: Binders, acid reducers, enhances warfarin.

60 or under: 1.6mcg/kg/day to start. ~50-150mcg daily
Over 60: 25-50mcg/day
CHD: 12.5-50mcg/day
Hospital: If pt is NPO, wait 3-5 days and IV dose is HALF THE ORAL DOSE

Question 3

Liothyronine

Answer 3

IND: Hypothyroidism, myxedema coma, TSH suppression
MOA: Synthetic T3
BOX: Not for weight loss, those doses are life threatening
CON: Uncorrected adrenal insufficiency, thyrotoxicosis, artificial rewarming of pts
ADR: Nothing unless the dose is too high = hyperthyroid s/s

Shorter half life and faster onset, peaks in 2-3 days. Taken 2x/day. 25mcg = 100mcg of levothyroxine

Question 4

Armour Thyroid, Nature-Thyroid

Answer 4

IND: Hypothyroidism
MOA: Dessicated animal thyroid glands; acts as endogenous T3/4. “More natural” and has potency and consistency concerns
BOX: Not for weight loss
CON: Thyrotoxicosis or uncorrected adrenal sufficiency
ADR: Same as hypothyroid drugs.
60mcg = 100mcg levothyroxine

Question 5

Liotrix

Answer 5

IND: Hypothyroidism
MOA: Synthetic t3/4
BOX: same as Levothyroxine
CON: same
ADR: same
No advantages

Question 6

Thionamides

Answer 6

IND: Hyperthyroidism
MOA: Blocks oxidation of iodine IN THE THYROID GLAND; stops T3/4 synthesis
BOX: n/a
CON: n/a
ADR: n/a
Takes up to 4 months for euthyroid state

Question 7

Methimazole

Answer 7

IND: Hyperthyroidism, first line EXCEPT PREGNANT OR THYROID STORM
MOA: Blocks oxidation of iodine IN THE THYROID GLAND; stops T3/4 synthesis (thionamide). No effect outside of thyroid. Longer half life and dosed 1x/day
BOX: n/a
CON:
ADR: Agranulocytosis. Can convert pt to hypothyroid state. Neonatal hypothyroidism.

Question 8

Propylthiouracil

Answer 8

IND: Hyperthyroidism in pregnancy and thyroid storm
MOA: Blocks oxidation of iodine IN THE THYROID GLAND, AND PERIPHERY
BOX: To USE it in pregnancy, instead of methimetazole
CON:
ADR: agranulocytosis, conversion to hypothyroid.
shorter half life, dosed 3-4 times/day

Question 9

Radioactive Iodine

Answer 9

IND: Hyperthyroidism
MOA: Emits Beta rays to destroy the thyroid
BOX: n/a
CON: Pregnancy and breast feeding
ADR: HUGE incidence of delayed hypothyroidism and treatment takes months

Question 10

Strong Iodide Solution

Answer 10

IND: Thyroidectomy, Thyroid storm
MOA: stops T3/4 synthesis and release into the blood, and decrease iodide uptake by thyroid
BOX: n/a
CON: TB, dermatitis herpetiformis, vasculitis, nodular thyroid disease with heart disease
ADR: Hypothyroidism w/long term use

Question 11

Beta Blockers

Answer 11

Suppress tachy and s/s of Grave’s/Thyroid storm
Works faster than other treatments for symptomatic relief
Co-prescribed in thyroid storm every time unless CON
Can be added on in Grave’s