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Flashcards in Thyroid Deck (21)
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1

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

2

Hypothyroid Causes

T4 concentrations
TSH concentrations

Hashimoto's thyroiditis
Surgery
Meds (Lithium, RAI, Amiodarone)
Iodine deficiency

Decreased total and free T4
Elevated TSH

3

MILD (Subclinical) Hypothyroidism

-TSH above upper limit (but <10)
-normal FT4
-no overt s/s

4

Levothyroxine

Gold-standard for treating hypothyroid
full replacement dose 1.6 mcg/kg/day

**Renal - lower 25-50 mcg decrease
12 week onset

5

Liothyronine

Synthetic t3, rarely needed. peak and trough = thyrotoxicosis after taking

6

Armour (animal thyroid)

nonphysiologic ratio, no role in modern therapy

7

Liotrix

LT4 and T3 combination; nonphysiologic ratio; no role in modern therapy

8

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

9

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

10

Overtreatment and Undertreatment of hypothyroid

overtreatment/suppressed TSH more common
--risk of afib, anxiety, depression, osteoporosis, fx

11

Thyrotoxicosis / hyperthyroid causes

Graves Disease
Thyroid stimulating antibodies
Meds (Amiodarone)

Elevated total and free T4
Suppressed TSH

12

Treating subclinical hyperthyroid

TSH < 0.1, Graves, post menopausal, underlying cardiovascular disease

(higher risk of cardio and bone sequelae)

otherwise test q 6 months

13

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)

14

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

15

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

16

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

17

Surgery- calcium replacement

1250-2500mg/day calcium and 0.5mcg/day of calcitriol
- can be tapered if pt does not develop hypoparathyroid

18

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)

19

Hyperparathyroid and peds

MMI (0.2 to 0.5 mg/kg/day

20

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

21

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)