Thyroid

Question 1

Where thyroglobulin is stored

Answer 1

colloid

Question 2

2 important TSH-inducible transcription factors

Answer 2

PAX-8, TTF-1

Question 3

alpha subunits that TSH GPCR is coupled to

Answer 3

Galpha-s (normal) and Galpha-q (only at high TSH levels)

Question 4

What is used to uptake iodide into follicular cells

Answer 4

Sodium-iodide symporter (NIS): 2Na for every 1 iodide

Question 5

Enzyme that oxidizes iodide using H2O2 and is localized on the apical side of the thyrocyte (near the colloid) and also allows coupling of 2 tyrosine rings (oxidative condensation)

Answer 5

Thyroid peroxidase (TPO)

Question 6

The predominant thyroid hormone in circulation

Answer 6

T4

Question 7

The active form of thyroid hormone that has much higher affinity for thyroid receptor

Answer 7

T3

Question 8

Enzymes that convert T4 to T3 within target cells

Answer 8

Deiodinases

Question 9

Synthetic T4

Answer 9

levothyroxine

Question 10

Synthetic T3

Answer 10

liothyronine

Question 11

2 thionamides used to treat hyperthyroidism

Answer 11

methimazole, propylthiouracil

Question 12

Target of thionamides

Answer 12

thyoid peroxidase, thus inhibiting iodination of thyroglobulin and coupling of MIT and DIT to generate T3 and T4

Question 13

Additional mechanism of propylthiouracil besides targeting TPO

Answer 13

Inhibits D1 and D2, inhibiting peripheral conversion of T4 to T3

Question 14

MOA of radioactive iodine

Answer 14

Uptake by NIS and concentrated in the colloid where it emits beta particles that destroy the follicle

Question 15

Ionic inhibitor used for hyperthyroidism that competitively inhibits NIS

Answer 15

Perchlorate

Question 16

Primary function of thyroid hormones

Answer 16

Maintain metabolism in the body

Question 17

Function of hypothalamus in thyroid regulation

Answer 17

Releases thyrotropin-releasing hormone (TRH)

Question 18

Function of the pituitary in thyroid regulation

Answer 18

releases thyrotropin, also known as thyroid-stimulating hormone (TSH)

Question 19

Normal TSH level

Answer 19

0.5 - 2.5 mcgU/mL

Question 20

Normal T4 levels

Answer 20

0.7-1.9 Ngo/mL

Question 21

autoimmune hypothyroidism

Answer 21

Hashimoto’s disease

Question 22

The precursor for thyroid hormones

Answer 22

Thyroglobulin (TG)

Question 23

Normal starting dose of levothyroxine for hypothyroidism

Answer 23

1-1.6 mcg/kg/day (use IBW for obesity)

Question 24

Starting levothyroxine dose for elderly and patients with CVD

Answer 24

25-50 mcg

Question 25

Reason why synthetic T4 (levothyroxine) is used over synthetic T3 (liothyronine)

Answer 25

half-life of T4 is 6-7 days, whereas T3 is only 2 days

Question 26

How often TSH/free T4 should be monitored in a pt with uncontrolled hypothyroidism

Answer 26

every 6-8 weeks

Question 27

How much should a levothyroxine dose be titrated by

Answer 27

10-20%

Question 28

How often TSH/free T4 should be checked in a patient with controlled hypothyroidism

Answer 28

annually or if symptoms

Question 29

Levothyroxine dose conversion from PO to IV

Answer 29

Give 1/2 of normal PO dose

Question 30

Dose of levothyroxine if a patient has subclinical hypothyroidism (TSH 5-10 mcgU/mL)

Answer 30

25-50 mcg/day

Question 31

Very advanced hypothyroidism with very high TSH linked to 60-70% mortality

Answer 31

myxedema coma

Question 32

Treatment of myxedema coma

Answer 32

IV levothyroxine and corticosteriods

Question 33

Autoimmune hyperthyroidism

Answer 33

Grave's disease

Question 34

3 drugs that can cause hypothyroidism

Answer 34

1. lithium 2. amiodarone 3. interferon-alpha

Question 35

BB that can be used for symptomatic relief of tachycardia associated with hyperthyroidism and also inhibits peripheral conversion of T4 to T3

Answer 35

Propranolol

Question 36

Thionamide that is preferred in pregnancy

Answer 36

Propylthiouracil

Question 37

Labs needed for thionamide monitoring

Answer 37

1. TSH/fT4 every 4-6 weeks 2. LFTs 3. CBC (if reason such as cough or fever)

Question 38

3 parts of treatment for thyroid storm (severe thyrotoxicosis)

Answer 38

1. IV BB and iodide 2. Methimazole or PTU 3. hydrocortisone