EXAM #1: HYPOTHYROID

Question 1

What are the major steps of thyroid hormone synthesis?

Answer 1

1) Trapping of iodide (NIS)
2) Organification (add I to thyroglobulin)
3) Coupling (MIT and DIT)
4) Storage (Colloid)
5) Secretion

Question 2

What is the Jod Basedow effect?

Answer 2

Increased T4 formation with Iodide concentration

Question 3

What is the Wolff-Chalikoff effect?

Answer 3

Decreased T4 formation with increased iodide, after initial increase

Question 4

What is the escape effect?

Answer 4

Increased T4 formation AFTER wolff-chalikoff effect

Question 5

What subunit of TSH gives the hormone its specificity?

Answer 5

Beta

Question 6

Aside from TSH, what else can be increased by TRH?

Answer 6

Prolactin

Question 7

What factors increases TGB?

Answer 7

1) Estrogen (pregnancy, BCP)

2) Congenital

Question 8

What factors decreases TGB?

Answer 8

1) Systemic illness

2) Glucocorticoids

Question 9

What is the best test of thyroid function?

Answer 9

TSH

*Note that this will be inversely proportional to thyroid function

Question 10

What are the expected values of TSH and free T4 in hypothyroidism?

Answer 10

• High TSH
• Low FT4

*Note that the TSH will be above the reference range before FT4; thus, more sensitive

Question 11

What are the expected values of TSH and free T4 in hyperthyroidism?

Answer 11

• Low TSH
• High FT4

*Note that the TSH will be below the reference range before FT4; thus, more sensitive

Question 12

What is the utility of radionuclide scans in evaluating the thyroid?

Answer 12

This is used to determine thyroid function

Question 13

What does “subclincal” refer to in regards to interpreting the results of FT4 and TSH levels?

Answer 13

Changes in TSH with normal FT4

Question 14

What labs are associated with primary hypothyroidism?

Answer 14

• High TSH

- Low T3/4

Question 15

What are the possible etiologies of primary hypothyroidism?

Answer 15

1) Thyroiditis
2) Iodine deficiency
3) Radiation
4) Surgery
5) Infiltrative
6) Drugs

Question 16

What are the possible etiologies of secondary hypothyroidism?

Answer 16

1) Surgical
2) Infiltrative/ metastatic
3) Radiation therapy
4) Apoplexy

Question 17

What will the TSH and T4 be in secondary hypothyroidism?

Answer 17

• LOW TSH

- Low T4

Question 18

What is a delayed relaxation phase?

Answer 18

Testing DTR, takes a long time for muscles to relax

*Associated with hypothyroidism

Question 19

What is the most common cause of hypothyroidism in iodine-sufficient areas?

Answer 19

Hashimoto’s Thyroiditis

Question 20

What is Hashimoto’s Thyroiditis?

Answer 20

Auto-immune destruction of the thyroid

Question 21

What are the major clinical features of Hashimoto’s Thyroiditis?

Answer 21

1) Goiter

2) Bossillated feel

Question 22

What antibody is usually elevated in Hashimoto’s Thyroiditis?

Answer 22

TPO antibodies

*Note that these are NOT required for diagnosis

Question 23

What is the hallmark US finding in Hashimoto’s Thyroiditis?

Answer 23

Heterogenous appearance

Question 24

What causes goiter in iodine-related hypothyroidism?

Answer 24

• Deficiency= gland has to work harder

- Increased TSH= increases size of thyroid gland

Question 25

What is the name of the effect that can cause iodine to lead to hypothyroidism?

Answer 25

Wolff-Chaikoff phenomenon

Question 26

How is hypothyroid treated?

Answer 26

Levothyroxine (T4) | Roughly 1.5 mcg/kg/day

Question 27

When is treatment indicated for hypothyroidism?

Answer 27

TSH greater than 10

Question 28

If the TSH is below 10 but the patient is symptomatic, what should you do?

Answer 28

Give a levothyroxine trial

Question 29

When treating hypothyroid, how long should you wait to check a TSH after a dose change?

Answer 29

4-6 weeks *UNLESSS, patient switches brands of medication, starts birth control, or is pregnant

Question 30

What is Liothyronine?

Answer 30

T3 *Note that this is not usually recommended as therapy

Question 31

What is contained in "natural" thyroid sources, such as Armour Thyroid?

Answer 31

Both T3 and T4

Question 32

How do the thyroid hormone needs change in pregnancy?

Answer 32

Needs for thyroid hormone increase

Question 33

Clinically, what do you need to do with pregnant patients regarding thyroid?

Answer 33

1) Check TSH at diagnosis of pregnancy 2) Monitor TSH 4-6 weeks 3) Doses redcuced post delivery

Question 34

What is myxedema coma?

Answer 34

Acute medical emergency w/ 1) Mental status change 2) Hypothermia 3) Hypoglycemia 4) Resp. failure 5) Hypotension 6) Bradycardia *More common in women, precipitated by infection, CVA, or MI

Question 35

What is the treatment for myxedema coma?

Answer 35

1) Supportive measures/ tx of underlying cause 2) IV thyroxine replacement 3) Hydrocotisone

Question 36

What should you use to guide dose adjustments in secondary hypothyroidism?

Answer 36

Free T4

Question 37

What should T4 NOT be used for?

Answer 37

1) Shrinking nodules 2) Weight loss 3) Treating depression 4) Lowering cholesterol