Thyroid Flashcards
Thyroid Test Levels
TSH
FT4
Anti-TPOAb/AntiTGAb
TSI (TSHR-SAb)
TSH - Gold Standard
0.5 - 4.5 mIU/L
FT4- 0.7 - 1.9 ng/dL
Anti-TPOAb - Variable / autoimmunie hypothyroid
TSI - undetectable - Confirms Graves
Hypothyroid Causes
T4 concentrations
TSH concentrations
Hashimoto’s thyroiditis
Surgery
Meds (Lithium, RAI, Amiodarone)
Iodine deficiency
Decreased total and free T4
Elevated TSH
MILD (Subclinical) Hypothyroidism
- TSH above upper limit (but <10)
- normal FT4
- no overt s/s
Levothyroxine
Gold-standard for treating hypothyroid
full replacement dose 1.6 mcg/kg/day
**Renal - lower 25-50 mcg decrease
12 week onset
Liothyronine
Synthetic t3, rarely needed. peak and trough = thyrotoxicosis after taking
Armour (animal thyroid)
nonphysiologic ratio, no role in modern therapy
Liotrix
LT4 and T3 combination; nonphysiologic ratio; no role in modern therapy
Use of LT4 and dosage
–general replacement
younger than 65 years w/ overt
> 65
w/ ischemic HD
newborns
Overt thyroid
Asymptomatic but--
Cardiovascular issues
pregnant
\+ TPOAb
25-50 mcg/day and titrate every 6-8 weeks based on TSH
<65 w/ overt –> 1.6-1.8 mcg/kg/day (ideal weight for fattys)
> 75 –> 1 mcg/kg/day [25-50 mcg/day, then titrate]
Heart Disease - 12.5 - 25 mcg/day and titrate
newborn- 10-15 mcg/kg/day
Target TSH w/ treatment
adjustment percent
0.5 - 2.5 mIU/L
adjust 10%-20% if out of range and re-check TSH 6-8 weeks later
Overtreatment and Undertreatment of hypothyroid
overtreatment/suppressed TSH more common
–risk of afib, anxiety, depression, osteoporosis, fx
Thyrotoxicosis / hyperthyroid causes
Graves Disease
Thyroid stimulating antibodies
Meds (Amiodarone)
Elevated total and free T4
Suppressed TSH
Treating subclinical hyperthyroid
TSH < 0.1, Graves, post menopausal, underlying cardiovascular disease
(higher risk of cardio and bone sequelae)
otherwise test q 6 months
Beta-blockers & Hyperthyroid
rapid relief of symptoms r/t Beta-Adrenergic system
- only used until better option
- propranolol and nadolol (nonselective preferred)
do not use in HF or ashma; use B-1 specific if contraindicated (metoprolol, atenolol)
Iodide
time of effect
-uses
contraindication
- t4 levels reduced in 24 hours
- lasts 2-3 weeks
- graves before surgery (7-14 days before) and thyroid storm
C/I - radioactive iodine treatment
s/e - hypersensitivity “iodism” – weight loss, depression, gynecomastic
PTU and MMI (Thionamide) [preference?]
- How they work
- Half life
- uses
- PTU beneft v MMI
- Relapse
S/e
Tx of bad s/e
interfere w/ thyroid hormone synthesis
- longer in MMI (6-9 hours)
- Methimazole (MMI) preferred tx (Radioactive iodine is considered after control with antithyroid drugs)
primary therapy for graves or preparative therapy pre-sx / iodine admin
PTU - inhibits t4 to t3;
MMI- signle daily dose, less hepatotoxic
Relapse common, esp. preggo - have plan in place,
-immunosuppressant, *Agranulocytosis (diff then temp WBC decrease - always within 3 months of therapy; fever, malaise, sore throat, ANC <1000) [sepsis and death]
if agranulo – d/c medicine, start on broad abx and filgastrim
Radioactive iodine
thyroid storm-prevention
dosage
contraindicated
ablation; common to develop hypothyroid, 6-8 weeks to work
give w/ beta blockers (take throughout) and MMI (wean off and on)
dose- weight of gland (10-15 mCi)
–c/i in pregnancy, give prednisone w/ eye disease
Surgery- calcium replacement
1250-2500mg/day calcium and 0.5mcg/day of calcitriol
- can be tapered if pt does not develop hypoparathyroid
Hyperparathyroid and preggo
give PTU in first trimester, can switch to MMI in 2-3 trimester
antithyroid therapy can suppress fetal thyroid function
switch to MMI after birth (hepatotoxicity)
Hyperparathyroid and peds
MMI (0.2 to 0.5 mg/kg/day
Thyroid Storm - Cause, Symptom and Treatment
previously hyperthyroid pt by infection, trauma, sx, radioactive iodine, or sudden withdrawal
High fever, tachycardia, tachpnea, dehyrdation ,delirium, coma
Beta blockers, IV or oral iodide, large doses of PTU or MMI
Drug-Induced Thyroid Abnormal Amiodarone Lithium Interferon-A Tyrosine Kinase Inhibitor (TKI)
A-causes subclinical hypothyroid but can resolve.
-if cant stop, LT4 helps
Hyper thyroid in iodine deficient areas
*monitor baseline thyroid labs
L- 34% of pts get hypothyroid, can occur whenever; may need LT4
I- hypothyroid in 39% treated for hep C (hyper than hypo)
