Treatment of Thyroid dz Flashcards
function of the thyroid
metabolic rate. Iodine uptake, thyroglobulin production. Hormone secretion T3 and T4
thyroid physiology
iodide transport into thyroid–>thyroid peroxidase oxidized iodide–>Binds to iodinated tyrosine in thyroglobulin–>Combone to form T3 T4—>further breakdown of T4 to T3
What is feedback loop for thyroid homeostasis?
Hypothalmic pituitary thyroid axis - negative feedback.
Drugs that increase TBG will mean?
Less free thyroid hormone (more binding will occur)
Increase serum TBG is the result of?
Estrogen, Tamoxifen, Heroin, Methadone, Mitotane, Fluorouracil
Decreased serum TBG is result of?
Androgens, Anabolic steroids, Slow release nicotinic acid, Glucocorticoids
diagnostic criteria for hyperthyroidism
Decreased TSH, Increased T3 and T4 (free and total)
TX for hyperthyroidism
ATD, RAI, Surgery, Smptomatic (Beta-blockers)
What is first line tx for hyperthyroidism?
Thioamides, Methimazole for most PTU for thyroid storm of 1st trimester moms.
MOA Thioamides
inhibits thyroid synth. Depletes stored hormon.
PTU-inhibits T4 to T3 conversion within hours. For pregnant pt’s -PTU preferred in 1st trimester. When breastfeeding Methimazole is preferred PTU can cause hepatotoxicity
Dosing of Thioamide (methimazole)
Methimazole: Initial Mild: 15mg/day Moderate: 30-40 mg/day Severe: 60 mg/day Continue 4-8 weeks until euthyroid
Maintenance: 5-15mg/day
Dosing of PTU
Intial :
100-150mg q 6-8h
Continue 4-8wks until euthyroid
Maintenance:
50-150mg/day
when should you test TSH after starting a pt on thioamides?
Don’t test for first 2-3 mos. Not accurate
When should you test for T4 after starting pt on thioamides?
4-8 weeks after starting. After remission (1year normal values) can follow up every 6-12mos.
P’Kinetics of Thioamides
A: well absorbed from GI tract
D: Concentrates in Thyroid, 80% protein bound PTU
M: Liver
E: Renal
H: methimazole 5-13 hours, PTU 1-2 hours
ADE thioamides
GI upset Arthralgia Rash, urticaria, pruritis Serious: Agranulocytosis, Hepatotoxicity
Caution with PTU
Watch for: Hepatotixicity, jaundice, joint pain, and pain etc. Check LFT’s, WBC’s Free T4
How soon should TSH be tested a after patient achieves remission?
2-3 mos.
Iodides MOA
Inhibits thyroid hormone release
Decrease thyroid hormone synthesis
Decrease thyroid gland vascularity
initial effect within 24 hours max 10-15 days of continuing therapy.
Uses for iodides in thyrotoxicosis
Reduced vascularity prior to thyroid surgery
prepare patients with Graves Dz for surgery
Decrease thyroid iodine accumulation in thyrotoxic crisis
prevent thyroid uptake of RI
ADE for Iodide
Rash, GI upset, Parasthesia, Immune hypersensitivity rx, Salivary gland swelling.
Iodism-burning in mouth or throat, metallic taste, sore teeth and gums, cold symptoms
MOA Lithium
Blocks T4 and T3 from release of gland-not recommended in ATA/AACA guidelines. d/t adverse effects
What do Beta Blockers do for pt’s with hyperthyroid?
Symptomatic treatment of palpitations, tachycardia, tremor, heat intolerance. Tx/ for thyrotoxicosis, thyroid storm, mono therapy for thyroditis
MOA beta blockers
Blocks beta adrenergic receptors to stop thyrotoxicosis