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Endocrinology/Nutrition > 03a: Thyroid > Flashcards

03a: Thyroid Flashcards

1
Q

Thyroid hormones contain (X)% (iodide/iodine).

A

X = 60-65

Iodine

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2
Q

(X) enzyme (oxidizes/reduces) (iodide/iodine) and organifies the product by attaching (Y).

A 
X = thyroid peroxidase (TPO)
Oxidizes Iodide (into iodine)
Y = thyroglobulin
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3
Q

Thyroid: (X) enzyme couples MIT and DIT to form (Y).

A 
X = thyroid peroxidase (TPO)
Y = T3 (DIT+MIT) or T4 (2DIT)
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4
Q

T/F: A small portion, about 10%, of T3 is made by peripheral conversion of T4 to T3.

A

False - 80% is made in this manner

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5
Q

(X) enzyme converts T4 to T3

A

X = D1 deiodinase (kidney and liver)

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6
Q

T/F: T3 is 20-100x more bioactive than T4.

A

True

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7
Q

T/F: rT3 is biologically inactive

A

True

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8
Q

T/F: MIT and DIT are biologically inactive.

A

True

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9
Q

(X)% of T4 is free; the rest is bound to (Y).

A 
X = 0.04
Y = TBG, transthyreitin, or albumin
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10
Q

Thyroid hormone acts at the
(hypothalamus/pituitary) to inhibit
secretion (X).

A

Both

X = TRH and TSH

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11
Q

Pregnancy may change thyroid hormone requirements due to (increase/decrease) in thyroid binding proteins

A

Increase

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12
Q

Cirrhosis and nephrotic syndrome may change thyroid hormone requirements due to (increase/decrease) in thyroid binding proteins

A

Decrease

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13
Q

OCP may change thyroid hormone requirements due to (increase/decrease) in thyroid binding proteins

A

Increase

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14
Q

T/F: T3 acts via RTK similar to IGF1.

A

False - intranuclear receptor

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15
Q

(X) is the BEST test to determine thyroid function because for every 2-fold change in (Y), there is a 100-fold change in (X).

A 
X = TSH
Y = free T4
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16
Q

Autoimmune Hypothyroidism is associated with Ab against (X)

A

X = TPO

17
Q

Most common cause of mental retardation worldwide

A

Hypothyroidism (due to iodine deficiency)

18
Q

90% of neonatal hypothyroidism is due to which cause?

A

Dysgenesis/Agenesis of thyroid (missing or severely underdeveloped)

19
Q

About 10% of neonatal hypothyroidism is due to (X). What would you see on imaging?

A

X = Dyshormonogenesis (defects in thyroid hormone production; abnormal TPO activity)

Normally placed thyroid gland that’s normal size or enlarged (goiter)

20
Q

Sarcoidosis can cause hypothyroidism, most commonly (primary/secondary/tertiary). What are other etiologies?

A

Tertiary (level of hypothalamus)

Histiocytosis, tumors, radiation

21
Q

Most common cause of goiter worldwide is:

A

Iodine deficiency (hypothyroid)

22
Q

(X) receptor mutation is a rare cause of hypothyroidism due to thyroid hormone resistance

A

X = T3

23
Q

Pt Sx include mental retardation, hearing loss, and short stature. TSH levels are high, T4 levels are high. What is the likely cause of the (hypo/hyper)-thyroidism?

A

Hypothyroidism

Resistance to thyroid hormone (T3-R defect; v rare)

24
Q

T/F: HT is symptom of hypothyroidism

A

True

25
Q

T/F: Total and LDL cholesterol levels are decreased in hypothyroidism.

A

False - elevated

26
Q

List some GI issues associated with hypothyroidism

A
  1. Abd distension, constipation

2. Autoimmune atrophic gastritis (achlorhydria, pernicious anemia)

27
Q

What’s cretinism?

A

severely stunted physical and mental growth owing to untreated congenital hypothyroidism

28
Q

Standard Rx for hypothyroidism is:

A

Oral L-thyroxine (T4)

29
Q

Hypothyroidism: once patient is on Rx and reaches steady state, how often should (X) levels be checked?

A

X = TSH

6-12 months (unless symptoms occur)

30
Q

Hypothyroidism: the rate of T4 replacement depends on which factor(s)?

A

Age and risk of CAD (titrate slowly in elderly to prevent CV issues)

31
Q

Hypothyroidism: T4 dose is determined once which list of factors has been considered?

A
  1. Age/wt of pt
  2. Previous I-131 Rx
  3. Meds/pregnancy (increase thyroid hormone proteins)
  4. Diet/GI status that may interfere with T4 absorption
32
Q

Decompensated state of severe hypothyroidism can result in (X), with as high as 50% mortality.

A

X = Myxedema coma

33
Q

T/F: Pt presenting with Myxedema Coma has very low core temp so should be treated with heat blanket asap.

A

False!!! Avoid external warmth (sudden vasodilation and vascular collapse)

34
Q

Myxedema Coma: key first steps in treatment

A
  1. IV L-thyroxine
  2. IV fluids (w glucose)
  3. Assisted ventilation (warm, moist air)
35
Q

(X) Ab are the most specific

marker for Hashimoto’s.

A

X = Antimicrosomal antibodies against TPO

Antithyroglobulin Ab less specific

Endocrinology/Nutrition (10 decks)

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