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Flashcards in Thyroid and Diabetes intro Deck (36):
1

What is the chemical name for the hormone T3?

Liothyronine

2

Which is more pharmacologically active, T4 or T3? Which is more abundant?

T3 is more active, T4 is more abundant

3

Outline the synthesis of thyroid hormone from peroxidase

Peroxidase – oxidation of dietary iodine – iodination of tyrosine – thyroid hormone

4

What is thyroid hormone stored as?

Thyroglobulin

5

What releases TRH and TSH?

TRH – hypothalamus
TSH – pituitary

6

What is thyroid binding globulin?

The plasma protein that binds the majority of circulating T3 and T4

7

Name two common increasers of TBG

Pregnancy and oral contraceptives

8

Name a common decreaser of TBG

Anabolic steroids

9

List three functions of thyroid hormone

Stimulates protein synthesis, increases metabolic rate, increases sensitivity to catecholamines

10

How long does it take T4 (levothyroxine) to reach max efficacy?

10 days

11

How long does it take T3 (Liothyronine) to reach max efficacy?

24 hours

12

Which is "slower on and slower off", T3 or T4?

T4

13

How does the thyroid hormone dose change in pregnant individuals?

Pregnant females require nearly 50% more thyroid hormone due to increased TBG production

14

What is a typical initial dose of Synthroid?

50 to 100 µg adjusted every 30 days until TSH is normal

15

Why should thyroid hormone be taken on an empty stomach?

It sticks to food and is excreted

16

In which case should T3 be administered?

In thyroid emergencies (myxedema coma), T3 can be given IV

17

What is the effect of administering too much thyroid hormone?

Pseudo-hyperthyroidism causing a fib

18

How is pseudohyperthyroidism treated?

Discontinue medicine for seven days then recommence at lower dose

19

Why is Synthroid the preferred treatment for hypothyroidism?

Generic thyroid hormone may be significantly less biologically active

20

What is the chemical name for T4 hormone?

L – thyroxine

21

What are the hyperthyroid medications (Methimazole and PTU) method of action? How do they differ?

Inhibits the oxidation (activation) of thyroid hormone
Methimazole does not affect peripheral conversion of T4 to T3, while PTU cannot take effect until preformed T4 -T3 is exhausted

22

Which of the two hyperthyroid medications is taken 1 x a day and which is taken 3 x a day?

Methimazole – 1x a day
Propylthiouracil- 3x a day

23

Which hyperthyroid medication can be used to treat thyroid storm in high doses?

PTU – inhibits peripheral conversion of T4 to T3

24

What are the most common adverse effects of PTU?

Rash, dysphasia, agranulocytosis

25

When is iodine used?

Before thyroid surgery to firm up thyroid (negative feedback loop within thyroid causes involution)

26

What is the typical dose of iodine given preop?

Potassium iodide 60 mg Q8 hours for 10 to 14 days

27

When and how is radioactive iodine used?

Can be used to treat graves disease: selectively up taken by thyroid tissue, slowly destroys tissue, often induces hypothyroidism

28

How is thyroid storm most effectively treated?

With a nonselective beta blocker (Propanolol) IV or PO

29

How is thyroid storm treated (other than beta blocker)?

High-dose dexamethasone steroid will inhibit T4 conversion to T3

30

What is a risk of using dexamethasone to treat thyroid storm?

Can cause hyperglycemia due to steroid effect on blood glucose

31

What is hyperinsulinemia?

Increased production of insulin in people who consume excessive amounts of sugar (leads to hyperglycemia from down regulation)

32

Which cells secrete in store insulin?

Beta islet cells of pancreas

33

How is synthetic insulin made?

Either enzymatic modification of porcine insulin or recombinant technology

34

What bacteria is used in recombinant technology to produce insulin?

E. coli

35

Describe the 3 biological effects of insulin

Activates glucokinase and glucose phosphatase
Causes conversion of glucose to glycogen
Enhances arachidonic acid and K+ entry into cells

36

What is the general dosage rule for insulin?

One unit of insulin per kilogram of body weight per day