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DEMS Unit 4 > Thyroid Dysfunction > Flashcards

Thyroid Dysfunction Flashcards

1
Q

Treatments for Graves

A

Meds, radioactive iodine (I131– kills off cells), surgery

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2
Q

medications for Graves

A
  • antithyroid drugs–inhibit synthesis of thyroid hormone (methimazole, propylthiouracil)
  • beta blockers - reduce systemic hyperadrenergic symptoms and effects (tremor, palpitations)
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3
Q

preferred antithyroid drug

A

methimazole preferred due to PTU effects on liver

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4
Q

when might you use propylthiouracil instead of methimazole in Graves?

A

pregnant women

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5
Q

what symptom common between hypothyroid and hyperthyroid

A

fatigue

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6
Q

when to treat hypothyroidism with TSH

A

almost all will treat with TSH >10. WHether to treat between 5-10 mIU/L controversial

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7
Q

preferred medication for hypothyroid treatment

A

levothyroxine- synthetic T4

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8
Q

treatment goal for hypothyroidism

A

between 1-2.5

- somewhere in nl range

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9
Q

Myxedema coma

A

extreme hypothyroidism so severe it can progress to death unless diagnosed promptly and treated vigorously

  • usually inciting event
  • high mortality– endocrine emergency
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10
Q

Sxs of myxedema coma

A

decreased cardiac output, bradycardia, respiratory depression, edema, altered mental status, hypothermia, metabolic derangements

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11
Q

Does the thyroid produce more T3 or T4

A

T4 (80-100 micrograms/day compared to 3-6 micrograms per day)

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12
Q

Which thyroid hormone is more active

A

T3

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13
Q

Deiodinase

A

converts T4 to T3

types 1 and 2 convert T4 to T3, but type 3 converts T4 to rT3 (inactive)

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14
Q

how is thyroid hormone transported

A

in blood, most is bound to proteins (TBG, TBPA, albumin)

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15
Q

is there a higher concentration of T3 or T4 in the blood

A

T3 (0.2% total TH vs 0.02%)

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16
Q

proteins binding T4 in blood

A

thyroxine binding globulin(TBG), thyroid binding prealbumin (TBPA), albumin

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17
Q

proteins binding T3 in blood

A

Thyroxine binding globulin, albumin

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18
Q

halflives of T3 vs T4

A

T3 = 1 day vs 7 days for T4

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19
Q

Causes of increased total T4 and total T3

A
  • hyperthyroidism/thyrotoxicosis
  • increased binding proteins (i.e. Estrogen increased like in pregnancy)
  • thyroid hormone resistance (rare)
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20
Q

causes of increased free T4 and free T3

A

hyperthyroid/thyrotoxicosis and thyroid hormone resistance

** binding protein issues not important

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21
Q

causes of decreased total or free T4 and T3

A
  • hypothyroidism
  • decreased serum protein binding
  • Euthyroid sick syndrome (nonthyroidal illness)
  • drugs
  • liver or kidney disease (total T4, total T3)—mostly has to do with binding proteins
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22
Q

Euthyroid sick syndrome/nonthyroidal illness

A

pt is sick for some other reason and not underlying thyroid disease; have elevated circulating cortisol, free fatty acids, cytokines that cause upregulation or type 3 deiodinase, so you get inactivation of thyroid hormone
- also have mild central hypothyroidism– have nl to decreased TSH at pituitary

  • abnormal thyroid labs with inappropriately low TH (esp T3)and low or nl TSH
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23
Q

nl TSH level

24
Q

what test do we use to look at thyroid function

A

TSH level - single best screening test for thyroid dysfunction
- indicates person’s thyroid hormone ‘set point’

25
what is the relative level of TSH in primary hypothyroidism
elevated (lack of negative feedback)
26
what is the relative level of TSH in primary hyperthyroidism
suppressed (excess negative feedback)
27
when is TSH not reliable
abnormal pituitary (panhypopituitarism, TSHoma, idiopathic central hypothyroidism)
28
sxs of hyperthyroidism
nervousness, weight loss, change in appetite -- normally increased, fatigue, tremor, heat intolerance, palpitations, hyperdefecation, trouble sleeping, diaphoresis
29
Labs in Overt hyperthyroidism/thyrotoxicosis
increased free T4 and free T3 but low TSH
30
subclinical hyperthyroidism
low TSH but nl free T3 and T4
31
thyrotoxicosis
high levels of circulating thyroid hormone | - can be due to overproduction of T3, T4 or high release of preformed/stored T3 adn T4 (not true hyperthyroidism)
32
How to determine cause of thyrotoxicosis
- thyroid uptake and perhaps radioactive iodine scan - If TSH suppressed, should be no iodine uptake since TSH stimulates iodine uptake/synthesis of T3/T4 - "normal" or elevated iodine uptake in setting of low TSH is abnormal-- autonomous production -- True hyperthyroid - low uptake - hormone excess due to high release of preformed thyroid hormone
33
radioactive iodine uptake
gives info on category of hyperthyroidism/thyrotoxicosis
34
What does high iodine uptake in setting of low TSH mean
true hyperthyroid-- pattern gives info on etiology (Graves' vs hot nodule vs multinodular goiter)
35
Etiologies of Low uptake Hyperthyroidism
- Subacute thyroiditis (granulomatous thyroiditis (viral); de Quervain's) - Chronic lymphocytic thyroiditis (Hashimoto's), postpartum thyroiditis, - radiation-induced thyroiditis, - infectious thyroiditis, -Drug-induced thyroiditis, - ectopic thyrotoxicosis (factitious or struma ovarii)
36
etiology of high uptake hyperthyroidism with low TSH
- Thyrotropin receptor Ab (Graves'; Hashitoxicosis) - Thyroid autonomu (toxic adenoma, toxic multinodular goiter---MNG) - HCG (hydatidiform mole, choriocarcinoma) - TSH (TSH-oma --pit tumor, thyroid hormone resistance
37
which hyperthyroidism conditions are painful
Granulomatous thyroiditis, radiation-induced thyroiditis, infectious thyroiditis
38
Graves disease
type of hyperthyroidism where you have Ab to TSH receptor, constantly activating it to make more thyroid hormone
39
Destructive thyroiditis
examples = subacute/granulomatous and postpartum
40
clinical course of destructive thyroiditis
have initial hyperthyroid phase with high free T4 and low TSH then transition to low free T4 with high TSH - about 20-25% remain hypothyroid
41
labs in overt hypothyroidism
elevated TSH, low free T4
42
subclinical hypothyroidism
high TSH but nl free T4; small decrease in T4 can have a large increase in TSH
43
sxs of hypothyroidism
mental slowness, weight gain, appetite change- usually decreased, fatigue, muscle cramps, cold intolerance, bradycardia, constipation, hypersomnia, dry skin
44
main categories of hypothyroidism
primary and central (secondary/tertiary)
45
etiologies of primary hypothyroidism
- Chronic autoimmune (Hashimoto's) thyroiditis - Transient hypothyroidism (silent or postpartum thyroiditis, subaute or granulomatous thyroiditis) - iatrogenic (thyroid surgery/thyroidectomy, radioactive iodine, external neck irradiation) - iodine deficiency or excess - drugs - infiltrative diseases - infections - congenital
46
drugs that can cause hypothyroidism
antithyroid, lithium, amiodarone, tyrosine kinase inhibitors, Fe, cholestyramine, phenytoin, carbamazepine
47
infiltrative diseases causing hypothyroidism
hemochromatosis, sarcoidosis, amyloidosis, fibrous (Reidel's) thyroiditis, scleroderma
48
infections that can cause hypothyroidism
M. tuberculosis, P. carinii
49
Hashimoto's thyroiditis
autoimmune condition where you have antibodies that destroy the thyroid's ability to make thyroid hormone
50
Thyroid autoantibodies in Hashimotos
TPO (thyroid peroxidase) Tg (thyroglobulin) - some have anti- TSHR Ab (thyroid stimulating hormone receptor Ab)
51
is hypothyroidism more common in males or females
females
52
what thyroid antibodies are present in Graves' disease
- most have Anti-TSHR Ab | - some also have Anti-TG (50-80%)and Anti-TPO (50-80%)
53
what other conditions besides Graves and Hashimoto's might you see thyroid antibodies
- normal population (TG, TPO) - relatives of those with autoimmune thyroiditis (TG, TPO) - Type I DM (TG, TPO) - Pregnant women (TG, TPO)
54
positive thyroid Ab with elevated TSH, what proportion develop hypothyroidism
rate of 5% per year. If just Abs alone ~2% per year
55
hypothyroid treatment goal
~ 0.5-3

DEMS Unit 4 (16 decks)

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