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Endocrine > EXAM #1: HYPOTHYROID > Flashcards

EXAM #1: HYPOTHYROID Flashcards

1
Q

What are the major steps of thyroid hormone synthesis?

A

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

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2
Q

What is the Jod Basedow effect?

A

Increased T4 formation with Iodide concentration

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3
Q

What is the Wolff-Chalikoff effect?

A

Decreased T4 formation with increased iodide, after initial increase

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4
Q

What is the escape effect?

A

Increased T4 formation AFTER wolff-chalikoff effect

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5
Q

What subunit of TSH gives the hormone its specificity?

A

Beta

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6
Q

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

A

Prolactin

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7
Q

What factors increases TGB?

A

1) Estrogen (pregnancy, BCP)

2) Congenital

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8
Q

What factors decreases TGB?

A

1) Systemic illness

2) Glucocorticoids

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9
Q

What is the best test of thyroid function?

A

TSH

*Note that this will be inversely proportional to thyroid function

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10
Q

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

A
  • High TSH
  • Low FT4

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

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11
Q

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

A
  • Low TSH
  • High FT4

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

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12
Q

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

A

This is used to determine thyroid function

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13
Q

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

A

Changes in TSH with normal FT4

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14
Q

What labs are associated with primary hypothyroidism?

A
  • High TSH

- Low T3/4

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15
Q

What are the possible etiologies of primary hypothyroidism?

A

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

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16
Q

What are the possible etiologies of secondary hypothyroidism?

A

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

17
Q

What will the TSH and T4 be in secondary hypothyroidism?

A
  • LOW TSH

- Low T4

18
Q

What is a delayed relaxation phase?

A

Testing DTR, takes a long time for muscles to relax

*Associated with hypothyroidism

19
Q

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

A

Hashimoto’s Thyroiditis

20
Q

What is Hashimoto’s Thyroiditis?

A

Auto-immune destruction of the thyroid

21
Q

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

A

1) Goiter

2) Bossillated feel

22
Q

What antibody is usually elevated in Hashimoto’s Thyroiditis?

A

TPO antibodies

*Note that these are NOT required for diagnosis

23
Q

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

A

Heterogenous appearance

24
Q

What causes goiter in iodine-related hypothyroidism?

A
  • Deficiency= gland has to work harder

- Increased TSH= increases size of thyroid gland

25
Q

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

A

Wolff-Chaikoff phenomenon

26
Q

How is hypothyroid treated?

A

Levothyroxine (T4)

Roughly 1.5 mcg/kg/day

27
Q

When is treatment indicated for hypothyroidism?

A

TSH greater than 10

28
Q

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

A

Give a levothyroxine trial

29
Q

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

A

4-6 weeks

*UNLESSS, patient switches brands of medication, starts birth control, or is pregnant

30
Q

What is Liothyronine?

A

T3

*Note that this is not usually recommended as therapy

31
Q

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

A

Both T3 and T4

32
Q

How do the thyroid hormone needs change in pregnancy?

A

Needs for thyroid hormone increase

33
Q

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

A

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

34
Q

What is myxedema coma?

A

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

35
Q

What is the treatment for myxedema coma?

A

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

36
Q

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

A

Free T4

37
Q

What should T4 NOT be used for?

A

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

Endocrine (34 decks)

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