Thyroid Disorders Flashcards
Which is more potent? T3 or T4?
T3 is more potent than T4, but has a much shorter half-life
Role of thyroid gland?
One of the largest organs within the body’s endocrine system and is the only organ which contains cells that have the ability to ABSORB iodine
What regulates thyroid hormone production?
Thyroid stimulating hormone (TSH or Thyrotropin)
Effects of elevations of T4 levels?
Elevations in T4 levels => inhibits secretion of TSH and create a
negative feedback loop
Which is measured, T3 or T4? Why?
Free T4 (FT4) levels
This is the active form (T4)
Xtics of Hypothyroidism?
Deficiency of T4 => elevation in TSH
Xtics of Hyperthyroidism?
Oversecretion => low level of TSH
Main causes of Hypothyroidism?
Hashimoto’s dx - most common cause
Drugs (Amiodarone, Inteferons, Lithium, Nitroprusside, Tyrosine kinase inhibitors, Sunitinib - most notable)
Clinical s/sx of Hypothyroidism?
Cold intolerance
Dry skin
Fatigue
Weight gain
Hoarseness
Coarseness or loss of hair
Heavier than normal menstrual periods (menorrhagia)
Memory and mental impairment
Goiter
Myalgias
Weakness
Depression
Constipation
Bradycardia
Complications of Hypothyroidism?
CVD (cardiomyopathy, HF, hyperlipidemia, CAD)
Goiter
Depression
Infertility
Myxedema - intense cold intolerance, drowsiness, unconsciousness
Effects of hypothyroidism on body metabolism?
Hypothyroidism causes the body to SLOW down
T/4 u see classic sx of low metabolism - fatigue, weight gain
What’s the most common cause of Hypothyroidism?
Hashimoto’s dx
Diagnosis of Hypothyroidism?
Low free thyroxine (low FT4) - normal range 0.7-1.9 ng/dL
High thyroid stimulating hormone (high TSH) - normal range 0.3-3.0 mIU/L
Monitoring of hypothyroidism?
Check free T4 and TSH levels Q6-8 wks, until levels are normal
Then 6 months later, then yearly
What’s FDA pregnancy category A for hypothyroidism?
Levothyroxine
DOC in hyperthyroidism?
Levothyroxine (T4)
Imp to use a consistent preparation
What can be used to supplement Levothyroxine (T4)?
Liothyronine (T3, Cytomel and Triostat)
Or
Desiccated thyroid (T3 & T4, Armour Thyroid) - not usually favored
How should thyroid replacement therapies be used?
Take thyroid replacement in the morning, first thing, on an empty stomach, at least 30 mins b4 breakfast
Is iodine supplement used in mgt of hypothyroidism?
No!
List hypothyroid tx agents
Levothyroxine (T4) - (Synthroid, Levothroid, Levoxyl)
Thyroid Desiccated USP (T3 and T4) - (Armour Thyroid, Nature-Throid, Westhroid, NP thyroid, WP Thyroid)
Liothyronine (T3) -(Cytomel, Triostat) tablet, inj
Liotrix (T3 and T4 in 1:4 ratio) - (Thyrolar)
Brand name of Levothroxine (T4)? Used in hypothyroid tx?
Synthroid
Levothroid
Levoxyl
Are all generic Levothyroxine bioequivalent?
No!
Check AB-rating
IV to PO ratio of Levothyroxine?
IV to PO ratio = 1:2
Drugs that decrease thyroid hormone levels?
Aluminum (antacids)
Calcium
Cholestyramine
Iron
Mg
Multivitamins (containing ADEK, folate, iron)
Orlistat (Xenical, Alli)
Sevelamer
Sodium polystyrene (Kayexalate)
Sucralfate
Lanthanum
CBZ, phenobarbital, PHT, rifampin
SSRIs
Separate doses by 4 hrs
Effect of Thyroid hormone on anticoagulant?
Increases effect of anticoagulants (increased PT/INR with warfarin)
Effect of Thyroid hormone on Digoxin, Theophylline, Antidiabetic meds?
Reduce digoxin, theophylline levels and effect of antidiabetic agents
Xtics of Hyperthyroidism (Thyrotoxicosis)?
High FT4 and low TSH
Main causes of Hyperthyroidism?
Graves dx
Clinical s/sx of Hyperthyroidism?
Heat intolerance or increased sweating
Weight loss (or gain)
Agitation, nervousness, irritability, anxiety
Palpitations and tachycardia
Fatigue and muscle weakness
Freq bowel movements or diarrhea
Insomnia
Light or absent menstrual periods
Goiter
Thinning hair
Tremor
Exophthalmos (exophthalmia), diplopia
Drugs that can cause hyperthyroidism?
Iodine
Amiodarone
Interferons
Any pt taking excessive doses of any forms of any available forms of thyroid hormone
Tx of choice of for Grave’s dx?
Radioactive iodine (RAI-131)
Role of beta-blocker in grave’s dx?
Beta-blocker should be given first for sx control (to reduce palpitations, tremors and tachycardia)
Mao of Thionamides (used for Hyperthyroid tx)?
Inhibits synthesis of thyroid hormones by blocking the oxidation of iodine in thyroid gland
PTU also inhibits peripheral conversion of T4 to T3
Drugs used for hyperthyroid tx?
Propylthiouracil (PTU) - (Propyl-Thyracil)
Methimazole (Tapazole)
BBW of Propylthiouracil (PTU) - (Propyl-Thyracil) & Methimazole (Tapazole) - used for hyperthyroid tx?
Severe liver injury and Acute liver failure (with PTU)
SEs of Propylthiouracil (PTU) - (Propyl-Thyracil) & Methimazole (Tapazole) - used for hyperthyroid tx?
GI upset
SLE-like syndrome
Hepatitis
Agranulocytosis (rare) - see MD at once if u develop yellow skin, abdominal pain, high fever or severe sore-throat
How do u use Propylthiouracil (PTU) - (Propyl-Thyracil) & Methimazole (Tapazole) - used for hyperthyroid tx - in pregnancy?
Propylthiouracil (PTU) - (Propyl-Thyracil) - preferred in 1st trimester
Methimazole (Tapazole) - used in 2nd and 3rd trimesters
Due to increased risk of liver toxicity from PTU
Hyperthyroid tx preferred in thyroid storm?
Propylthiouracil (PTU) - (Propyl-Thyracil)
Is PTU first-line in hyperthyroidism?
No!
Except in pts who can’t tolerate other options or conditions where other antithyroid therapies are CI
Iodides - used in hyperthyroidism?
Potassium Iodide + Iodine Solution (Lugol’s solution) used off-label
Saturated soln of Potassium Iodide (SSKI, ThyroShield)
MOA of Iodides - used in hyperthyroidism?
Temporary inhibit secretion of thyroid hormones; T4 and T3 levels will be reduced for several weeks, but effect will it be maintained
What’s thyroid storm?
Life-threatening medical emergency caused by decompensated hyperthyroidism
S/sx of thyroid storm?
Fever > 103 degree F
Tachycardia
Tachypnea
Dehydration
Profuse sweating
Agitation
Delirium
Psychosis
Coma
Tx of thyroid storm?
PTU 900-1200mg PO - divided Q4-6 hrs
+
Inorganic iodide therapy such as, SSKI 3-5 drops PO Q8H or
Lugol’s soln 5-10 drops PO Q8H (iodine to be given 1 hr AFTER PTU)
+
Beta-adnerergic blockage (eg. Propranolol 40-80 mg PO Q6H)
+
Corticosteroid therapy (eg. Dexamethasone 2-4 mg PO Q6H)
+
Aggressive cooling with APAP + cooling blankets + other supportive tx (eg. Antiarrhythmics, Insulin, Fluids, Electrolytes, etc)
Pregnancy category of Levothyroxine (Synthroid, Levoxyl)?
A
