Endocrine Conditions: Thyroid Disorders Flashcards
Two thyroid hormones produced by the thyroid gland are
T3 and T4
T3 formed from breakdown of T4
T3 = more potent than T4 but shorter half life
Thyroid hormone production regulated by….
TSH
Thyroid stimulating hormone (TSH)
Which Thyroid hormone is monitored in patients with thyroid disorders
Free T4 (FT4), unbound active form
Hypothyroidism is….
deficiency in T4 and elevation in TSH
more commonly in females (~80%)
Most common cause of Hypothyroidism is…..
Hashimoto’s disease, autoimmune condition where patients own antibodies attack the thyroid gland
Myxedema coma
uncommon but potentially fatal complication of hypothyroidism
treatment = IV Levothyroxine
Hypothyroidism lab results
Low free T4 = normal range 0.9 - 2.3 ng/dL
High TSH = normal range 0.3 - 3 mIU/L
How to monitor thyroid function in those receiving thyroid hormone replacement with drug txm
TSH every 4-6 weeks until normal then 4-6 months, then yearly
Drug of choice for Hypothyroidism is….
Levothyroxine = T4
Levothyroxine starting full replacement dose
1.6mcg/kg/day (IBW), titrate from there
Armour Thyroid is mix of…
T3 and T4 in variable amountsA
Armour Thyroid starting dose
15-30mg QD (15mg in cardiac disease) and titrate by 15mg.
usual doses 60-120mg
Levothyroxine PO notes
take with water at same time each day, at least 60min before breakfast or at bedtime 3hrs after last meal
Levothyroxine IV to PO conversion
0.75 to 1
Hypothyroidism txm
LEvothyroxine = T4
Thyroid Desiccated = T3 & T4
Liothyronine = T3
Hypothyroidism txm warnings
decrease dose in cardiovascular disease
Orangutans will vomit on you right before they become large proud giants
orange = 25
white = 50
violet = 75
olive = 88
yellow = 100
rose = 112
brown = 125
turquoise = 137
blue = 150
lilac = 175
pink = 200
green = 300
Drugs that decrease levothyroxine absorption
antacid and polyvalent cations containing iron, calcium, aluminum, mag, multivitamin, sevelamer and sucralfate = separate doses by 4 hrs
estrogen, SSRI, beta blockers, bunch more. top part most important
In hyperthyroidism, then FT4 is ____ and TSH is ____
FT4 is high
TSH is low
Most common cause of hyperthyroidism is….
Graves Disease
most common in females ages 30-50
autoimmune disease that stimulate Thyroid to produce too much T4
Drug induced causes of hyperthyroidism
iodine
amiodarone
interferons
Treating hyperthyroidism with antithyroid medications
take 1-3 months of high doses to control symptoms, once controlled dose should be reduced to prevent hypothyroidism
Propylthiouracil (PTU) mechanism of action
inhibits peripheral conversion of T4 to T3
Boxed warning for PTU
severe liver injury and acute liver failure
preferred in 1st trimester
Methimazole notes
drug of choice overall except in thyroid storm and preferred in 2nd/3rd trimester
Methimazole & PTU side effects
GI side effects
headache
rash
fever
constipation
When is iodine used?
usually in prep for thyroidectomy
it temporarily inhibits secretion of thyroid hormones but isn’t permanent
What blocks accumulation of radioactive iodine in thyroid gland and prevents thyroid cancer?
Potassium iodide
Thyroid storm
life threatening medical emergency characterized by decompensated hyperthyroidism
Signs and Symptoms of Thyroid storm
Fever > 103
Tachycardia
Tachypnea
Dehydration
Profuse sweating
Agitation
Delirium
Psychosis
Coma
Thyroid Storm treatment
PTU preferred (Loading dose 500-100mg + 250mg Q4h)
+
inorganic iodide therapy (SSKI = 5 drops in liquid) Q6h or Luqols solution = 4-8 drops Q6-8hr)
+
beta blocker (propranolol 40-80mg Q6h)
+
systemic steroid (dex 2-4mg Q6h)
+
aggressive cooling with APAP/ cooling blankets/other supportive treatments
Pregnancy and Hypothyroidism
Levo is preferred
will have to inc dose by 30-60% during pregnancy likely
Pregnancy and Hyperthyroidism
PTU = 1st trimester
Methimazole = 2nd and 3rd trimester
