Thyroid 2 Flashcards
(62 cards)
1
Q
What is acute suppurative thyroiditis?
A
- Thyroid inflammation due to bacterial but sometimes fungal infection, often L pyriform sinus fistula.
- Strep > staph > anaerobes»_space;> fungal
- Exam: warm tender thyroid with pain radiating to the ear
- Labs look for infection, thyroid labs can be all over the place
- Tx: Abx and possible I&D
2
Q
What is subacute or DeQuervain’s thyroidits?
A
- Thyroid inflammation due to a VIRAL infection.
- Exam: Painful thyroid gland
- Labs: Low TSH but not suppressed or hyperthyroidism –> euthyroidism –> hypothyroidism –> euthyroidism or permanent hypothyroidism
- Tx: NSAIDs or steroids
3
Q
How do hepatic hemangiomas affect thyroid function?
A
- They increase the activity of Type 3 deiodinase (think inactivation), which pushes T4 into rT3 and T3 into T2.
- Thus, some people call this a “consumptive hypothyroidism”.
4
Q
What is the Wolff-Chaikoff effect?
A
- A protective mechanism by which the body slows down organification of iodine in the thyroid, leading to lower levels of T4 and T3 in response to exogenous iodine.
- Can last up to 6 mos before there is escape.
5
Q
How does amiodarone affect the thyroid?
A
- Hypothyroidism: Occurs within the 1st year of tx due to decreased conversion of T4 –> T3 or via Wolf-Chaikoff effect.
- Hyperthyroidism (AKA Amiodarone-Induced Thyroiditis or AIT): Occurs mos to 3 years after tx. Type 1 AIT: Due to Jod-Basedow effect = patients w/ Graves will eat up the iodine from amio and make even more thyroid hormone leading to hyperthyroidism. Look for nodular goiter. Type 2: Inflammatory process due to high IL-6 levels which causes destruction of thyroid follicular cells and thus release of preformed thyroid hormone. Thyroid looks normal on exam.
6
Q
How do you dose levothyroxine?
A
- Neonate: 10-15 mcg/kg/d
- 3-6 mos: 8-10 mcg/kg/d
- 6-12 mos: 6-8 mcg/kg/d
- 1-3 yo: 4-6 mcg/kg/d
- 3-10yo: 3-4 mcg/kg/d
- 10-15yo: 2-4 mcg/kg/d
- Adults: 2-3 mcg/kg/d
7
Q
How do you dose levothyroxine for central hypothyroidism?
A
1.6 mcg/kg/d
8
Q
How does giving growth hormone affect thyroid function?
A
- GH causes increased somatostatin production, which will lower TSH production and thus cause hypothyroidism.
- Check TFTs before starting GH, 3-4 mos after starting, and then annually.
9
Q
What labs indicate a TSH adenoma?
A
High pituitary alpha glycoprotein
10
Q
How should you continue to check TFTs in children at risk for neonatal Graves?
A
- 3-5 DOL
- 10-14 DOL
- 1 MOL, 2 MOL, 3 MOL
11
Q
How do you treat neonatal graves using methimazole?
A
- Dose is 0.1-1.0 mg/kg/d but typically we give 0.2-0.5 mg/kg/d.
- Check TFTs q7d then q14d once stable
- Wean MMI once T4 and T3 are in normal range
12
Q
What B-blockers should be used to treat Graves disease and how do they work?
A
- Non-selective B-blocker (block B1 and B2): Propranolol, which also lowers conversion of T4 –> T3. Contraindicated in asthma given +B2 receptor.
- Selective B-blocker (blocks B1 only in heart): Atenolol or metoprolol (CNS penetration).
13
Q
What are the common side effects in order of commonality from methimazole?
A
- Rash
- Bone marrow suppression
- Liver toxicity
14
Q
What labs should you always check before starting methimazole?
A
CBC/d and LFTs
15
Q
When do you do RAI vs surgery?
A
- RAI: Must be 5+yo, minimal to no eye disease, no thyroid nodules, goiter <80g
- Surgery: The opposite.
16
Q
How do you prepare for thyroidectomy in someone with Graves disease?
A
- MMI for 1-2 mos
- Potassium iodide 1-2 drops TID for 10d before surgery
17
Q
What is familial non-autoimmune hyperthyroidism?
A
- Genetics: AD activating mutation of the TSH receptor on chromosome 14
- Phenotype: Goiter
18
Q
What is the thyroid exam like in Graves disease, Hashitoxicosis, subacute thyroiditis, and LT4 ingestion?
A
- Graves: Non-tender goiter.
- Hashitoxicosis: Non-tender goiter.
- Subacute thyroiditis: Tender goiter.
- LT4 ingestion: No goiter and non-tender.
19
Q
What are TFTs, TG levels, and uptake scan results like in Graves disease?
A
- TFTs: Overt hyperthyroidism
- TG: TG levels are high because the thyroid gland is being overly stimulated
- Scan: Increased uptake
20
Q
What are TFTs, TG levels, and uptake scan results like in Hashitoxicosis?
A
- TFTs: TSH low with normal or high T4/T3
- TG: all over the place
- Scan: decreased uptake
21
Q
What are TFTs, TG levels, and uptake scan results like in subacute thyroiditis?
A
- TFTs: TSH low with normal or high T4/T3
- TG: all over the place
- Scan: decreased uptake
22
Q
tender goiter =
A
subacute thyroiditis or acute suppurative thyroiditis
23
Q
What are TFTs, TG levels, and uptake scan results like in levothyroxine ingestion?
A
- TFTs: TSH low with high T4/T3
- TG: Low because TSH is not stimulating the thyroid
- Scan: decreased uptake
24
Q
Summarize euthyroid sick syndrome.
A
- Generally will have a low T3 and sometimes low T4 with inappropriately normal or low TSH. However, TSH can rise in the recovery phase.
- Type 1 deiodinase goes down, so have low T3.
- Type 3 deiodinase goes up, so you have high rT3.
25
What is TBG deficiency?
- Genetics: X-linked mutation in TBG on Xq22
- Labs: Total T3 and T4 are low while everything else is low. T3 uptake is elevated.
- Tx: None
26
What is TBG excess?
- Genetics: X-linked mutation in TBG on Xq22
- Labs: Total T3 and T4 are high while everything else is low. T3 uptake is low.
- Tx: None
27
What is familial dysalbuminemic hyperthyroxinemia?
- AD or AR mutation in ALB on 4q13, making albumin bind very tightly to T4 but not T3.
- Labs: Isolated total T4.
- Tx: None.
28
isolated elevated total T4 =
familial dysalbuminemic hyperthyroxinemia
29
hyperthyroidism + hypercortisolism in an infant =
McCune Albright
30
What is considered a normal I-123 scan?
up to 16% at 6 hours or up to 24% at 24 hours
31
- Pituitary hyperplasia due to longstanding hypothyroidism
- Tx w/ LT4
32
How do anticoagulants like heparin and lovenox affect TFTs?
- High T4
- High T3
- Normal TSH
33
How does biotin affect thyroid hormone levels?
Looks like hyperthyroidism (low TSH with high T4 and high T3)
34
isolated total T4 w/ no other lab abnormalities =
familial dysalbuminemic hyperthyroxinemia
35
What are the 2 types of assays used to detect Graves disease? Which is better to use?
- Receptor assays: Immunoassays that quantify the amount of IgG stuck to the TSH receptor.
- Bioassays: Measure amount of cAMP.
- Receptor/immunoassays are preferred.
36
goiter + ADHD =
thyroid hormone resistance
37
cobblestone appearance =
Hashimoto's
38
total T4 low and total T3 low with normal TSH
TBG deficiency
39
Which nucleus in the hypothalamus releases TRH?
PVN
40
Which thyroid levels are affected by obesity?
both TSH and T3 go up
41
How often do you check labs in patients with Graves disease according to age (neonate vs non-neonate)?
- Neonate: q7d until clinically stable, then q14d
- Everyone else: q2-6 weeks
42
What is the difference between TBG and TG?
- TBG is made by the liver
- TG is made by the thyroid
43
What are TFTs like in patients with lingual thyroid glands? How do you treat a lingual thyroid gland?
- Mild hypothyroidism
- Tx w/ LT4
44
How does TSH affect TG levels?
- TSH stims the thyroid gland to make more TG.
- However, TG also high in Graves as TSH receptor is being stimulated by antibodies.
45
What is the incidence of congenital hypothyroidism?
1:2,000 to 1:4,000
46
Which drugs affect TSH?
Decrease TSH: "Little DOppy DOG"
- Lithium, Dopamine, Octreotide, Dopamine agonists (bromocriptine, cabergoline), Opiates, Glucocorticoid
Increase TSH: My Low Cortisol
- Metoclopramide (reglan, which is a dopamine receptor blocker) + Cortisol low (Addison's)
47
How do thionamides work?
inhibit thyroid hormone synthesis by blocking TPO
48
Why does obesity cause elevated TSH?
obesity --> high leptin --> stims TRH --> stims TSH
49
What is familial non-autoimmune hyperthyroidism?
- AKA hereditary toxic thyroid hyperplasia
- AD activating mutation in TSH receptor (14q31)
- Phenotype: looks like Graves
- Labs: looks like Graves
50
elevated and isolated total T4 =
familial dysalbuminemic hyperthyroxinemia
51
What is familial dysalbuminemic hyperthyroxinemia?
- Genetics: AD mutation in the ALB gene, making albumin more attracted to T4 but not T3.
- Labs: All normal except elevated total T4. T3 uptake is normal since TBG is not affected in this disorder.
- Tx: None.
52
What causes a low T3 uptake? High T3 uptake?
- low = TBG excess
- high = TBG deficiency
53
What are normal total and free T3 values?
- TT3 = 60-180
- fT3 = 130-450
54
What is TBG excess?
- Genetics: X-linked mutation in Xq22 leading to excess production of TBG
- Labs: High TT3 and high TT4, low T3 uptake, everything else is normal
- Tx: None
55
What is TBG deficiency?
- Genetics: X-linked mutation in Xq22 leading to decreasedd production of TBG
- Labs: Low TT3 and low TT4, high T3 uptake, everything else is normal
- Tx: None
56
What are the classic lab findings in euthyroid sick syndrome?
- Low TT3 since Type 1 deiodinase activity is decreased
- Normal to low fT4
- High rT3 since Type 3 deiodinase activity is increased
- Normal to low TSH although it can rise during the recovery phase
57
What deiodinases are affected in euthyroid sick syndrome?
- Type 1 deiodinase activity is decreased, leading to lower TT3 levels.
- Type 3 deiodinase activity is increased, leading to higher rT3 levels.
58
How can you tell if a patient has factitious hyperthyroidism?
TG production would be low because normally Graves disease causes a high production of TG
59
low TG =
ingestion of LT4
60
How do you prepare for thyroidectomy in patients w/ Graves disease?
MMI and KI (1 drop TID) 10d before surgery
61
When would you use RAI ablation (I-131) vs thyroidectomy for the tx of Graves disease?
- RAI: limited eye disease, goiter <80g, no nodules, 5+yo
- Surgery: opposite
62
What is the Graves remission rate w/ MMI use?
20-30%
