Lec 3 Thyroid Physiology/Therapy Flashcards Preview

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Flashcards in Lec 3 Thyroid Physiology/Therapy Deck (32):
1

Tamoxifen

Perphenazine

Oral Contraceptives (Estrogen)

Increase TBG

 (thyroxine binding globulin)

--> Decrease Free T4

 

 

2

Phenytoin

Carbamazepine

Decrease TBG

 

Increase Free T4

free T4 = active thyroid hormones

3

Thyroid Lab Test

  • THYROID STIMULATING HORMONE (TSH)
    • most accurate and specific
  • Free T4
    • Used with TSH for initial diagnosis
  • Free T3
    • To see conversion abnormalities
  • Total T4
    • not useful

4

Hypothalamus

Produces TRH

TRH --> Pituitary

 

negative feedback from Thyroid Hormone

5

Pituitary

Secretes TSH

TSH--> Thyroid

 

negative feedback from T3/T4

6

Primary HypoThyroidism

Low fT4 / High TSH

Problem with the Thyroid Itself

7

Secondary / Tertiary (Central)

Hypothyroidism

low T4 / low TSH *rarely normal

Issue is higher up the chain

Pituitary or Hypothalamus issue

 

8

Thyroid Mediated HYPERthyroidism

HIGH T4 **or normal

Low TSH

HIGH T3

 

issue @ thyroid Level

9

TSH-Mediated HYPERthryoidism

ALL LEVELS HIGH

fT4 / TSH / T3

 

issue with pituitary

10

Radioactive Iodine Uptake Scan

RAIU

Adjunct Thyroid Function Test

Measures Iodine Utilization with radiolabled Iodide

Differentiates HYPERthyroidism etiology

graves disease

11

Tests for Autoimmunity

Presense of Thyroid AB's INDICATES AUTOIMMUNE PROCESS

but is not always SPECIFIC for a particular diagnosis/etiology

  • Anti-TPO (thyroid peroxidase) Antibodies
  • Thyroglobulin AB's
  • Antimicrosomal AB's
  • Thyroid Stimulating AB's (TSab)

12

Graves Disease

  • Autoimmune production of TSab
    • stimulate thyroid hormone production from thyroid
  • HYPERthyroidism
    • may REMIT, spontaneously
    • High T4 / Low TSH 
      • + Goiter / TSaB
  • 1st Line = Thioamides
    • 2nd = thyroidectamy / ablation

13

Toxic Multinodular Goiter

TMNG

  • HYPERthyroidism
    • >2 autonomous functioning thyroid nodules
      • --> secrete excess thyroid hormones
    • High T4 / Low TSH
  • 1st line = Thyroidectamy
    • since the nodule will always be there
  • 2nd line = thioamides

14

Toxic Thyroid Adenoma

  • HYPERthyroidism
    • Benign, HYPER-functioning thyroid tumor
      • can secrete Either T3 or T4 or BOTH
    • T4 can be low normal or high
      • TSH low
  • 1st line = thyroidectamy / radioactive Iodine
  • 2nd = Thioamides

15

Adjunct Treatment for HYPERthyroidism

These only treat SYMPTOMS

  • Adrenergic blockers
  • Beta blockers
  • CCBs

16

Thioamides

PTU / MMI

  • Block thyroid Synthesis
    • --> INHIBIT TPO
  • Dose adjustments
    • due to long half life of T4
    • Dose needed FLUCTUATES

17

Methimazole

First Line Therapy

Except in 1st trimester of pregnancy (PTU is preffered)

CROSSES PLACENTA & Appears in breast milk

  • 10x more potent than PTU
  • Longer half life, and higher concentration in thyroid gland

18

Propylthiouracil

PTU

INHIBITS PERIPHERAL T4-->T3 CONVERSION

along with Inhibiting TPO

Preferred in 1st trimester of pregnancy over MMI

19

Thioamide Adverse Reactions

  • Leukopenia
    • --> Agranulocytosis
  • Transaminitis
    • --> hepatoxicity
  • Rash

20

Potassium Iodide

Adjuct treatment for HYPERthyroidism

SSKI (super saturated potassium Iodide)

Lugols solution

 

CAN SHUT DOWN THYROID PRODUCTION

so we have to beware, only short term use

21

RAI

Radioactive Iodine

HYPERthyroidism

High chance of Secondary Hypothyroidism

22

Subtotaland Total THYROIDECTAMY

HYPERthyroidism treatment

surgical removal

leads to hypothyroidism

23

Pregnancy & HYPERthyroidism

INCREASED TBG --> decreased fT4

Radioactive therapy is contraindicated

Must maintain T4 levels for the baby

PTU for 1st Trimester

greater risk of preterm delivery and heart failure

24

Thyroid Storm

Acute Process

  • Treatment = throw everything at it
    • ​Thioamide
    • Beta Blockers
    • SSKI
    • Steroid

25

Hashimotos Disease

Hypothyroidism

Autoimmune disease with AB production against the thyroid

--> Fibrosis & decreased function of thyroid

26

Lab of Hypothyroidism

Decreased TT4 / fT4

Increased TSH

Possibly + Antibodies for Hashimtos

Increased Cholesterol

27

Hypothyroidism Pharmacotherapy

Levothyroxine Sodium (T4)

Liothyronine Sodium (T3)

Liotrix (4:1 Mixture)

Armour Thyroid (Natural Thyroid)

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Initiation & Dosage of

Levothyroxine

  • Aggressive Start
    • ◦50-125 mcg/day: younger, larger, severely symptomatic patients

  • Conservative

    • ◦12.5-25 mcg/day: older, smaller, risk for hyperthyroid complication

  • Symptomatic improvement is typically evident within 2 weeks

  • Aging may lead to reduction in dose due to T4 clearance

29

Conservative Dosing Approach

Levothyroxine

  • Elderly
    • --> can lead to HYPERthyroidism
      • ​--> OSTEOPOROSIS
      • ​​--> angina
  • ​​Patients with Pre-existing CAD
    • --> angina issues

30

Pregnancy

Levothyroixine

MORE TBG in pregnant women

due to INCREASE in estradiol concentration

INCREASE DOSE BY 50%

monitor TSH levels every 4 weeks and adjust dose

31

Myxedema Coma

Life- Threatening

Long-standing, uncorrected hypothyroidism

  • slow developing symptoms
  • Thyroid Replacement ASAP
    • ​MUST BE IV
      • due to reduced GI absorption

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