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2021-2022 Endo Review Rearr. > 176b/177b/178b - Thyroid Physio, Path, Pathopys, Nodules, Cancer > Flashcards

176b/177b/178b - Thyroid Physio, Path, Pathopys, Nodules, Cancer Flashcards

1
Q

What are the imaging modalities of choice for evaluating thyroid structure?

A

Ultrasound = first line

CT if there is intrathoracic extension of large goiters

Use iodine isotopes for thyroid function

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2
Q

Which thyroid neoplasm is derived from C-cells?

A

Medullary carcinoma of the thyroid

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3
Q

Which type of thyroid cancer is associated with a history of radiation exposure?

A

Papillary carcinoma of the thyroid

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4
Q

Which thyroid neoplasm is most likely to have a hereditary component?

A

Medullary thyroid carcinoma

  • Association with MEN-2
    • Mutation in RET oncogene
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5
Q

What is the most common cause of thyroid disease worldwide?

A

Iodine deficiency

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6
Q

A patient presents with bilateral pheochromocytoma

What organ will you check next to evaluate for neoplasm?

A

Thyroid

  • Bilateral pheo = high suspicion for MEN-2
  • MEN-2A and MEN-2B both have increased risk of medullary thyroid carcinoma in addition to pheochromocytoma
  • In addition:*
  • MEN-2A: look for parathyroid hyperplasia*

MEN-2B: look for marfinoid appearance, ganglioneuroma

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7
Q

What is the most common congenital thyroid nodule?

A

Thyroglossal duct cyst

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8
Q

How does biotin supplementation affect thyroid lab values?

(TSH, T3, T4)

Why?

A
  • Falsely low TSH
  • Falsely high T4, T3

Will lead to false diagnosis of Graves’ disease!

Biotin cleaves the assay antibody (something like this)

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9
Q

What is organification? (in the context of TH synthesis)

What enzyme is responsible?

A

Organification via TPO

  • Oxidation of I- to I2
  • Iodination: Attach I2 to tyrosine residues on thyroglobulin

Result = Thyroglobulin with MIT and DIT

Will be coupled by TPO as well: Combine MIT and DIT

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10
Q

Describe the histologic features of non-invasive follicular thyroid neoplasm (NIFTP)

What is the treatment?

A
  • Nuclear features of papillary thyroid carcinoma
    • Nuclear grooves
    • Psamoma bodies
    • Orphan Annie eye inclusions
  • Well encapsulated like follicular adenoma
    • Well-encapsulated (uniform, continuous, fibrous capsule)
  • Tumors are well-behavied
    • Act like follicular adenomas
  • Tx = lobecctomy
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11
Q

Which 3 proteins bind thyroid hormone in the blood?

A
  • Thyroid binding globulin (TBG)
  • Transthyretin
  • Albumin

Affinity: TBG > Transthyretin > Albumin

Note: only very small percentages of T4 and T3 are unbound

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12
Q

Describe the 24h iodine uptake pattern that is pathognomonic for Graves’ disease

A

Diffuse, homogenous uptake

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13
Q

What is the role of molecular testing in the evaluation of thyroid nodules?

A

Test intermediate-suspicion nodules for characteristic mutations

Most useful as rule-out tests for specific pathologies

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14
Q

Where in the body is the thyroid hormone receptor alpha (TR-alpha) found?

What about thyroid TR-beta?

A
  • TR-alpha
    • Brain
    • Skeletal tissues
    • Intestines
    • Heart
  • TR-beta
    • Liver
    • Heart
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15
Q

Describe the findings associated with Grave’s Disease

  • Gross:
  • Histology:
A
  • Gross:
    • Diffuse, symmetric enlargement
  • Histology:
    • Papillary hyperplasia
    • Tall follicular cells
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16
Q

What neoplasms are associated with MEN-2? (both 2A and 2B)

Which neoplasms are specific to 2A and 2B respectively?

A
  • All MEN-2
    • Medullary thyroic carcinoma
    • Pheochromocytoma (medulla of adrenal gland)
  • MEN-2A
      • Parathyroid hyperplasia
  • MEN-2B
      • Marfanoid appearance
      • Mucosal neuroma/ganglioneuroma
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17
Q

What is the histological hallmark of thyroid papillary caricinoma?

A

Atypical nuclear morphology

  • Nuclear grooves
  • Orphan Annie eye inclusions
  • Hypochromasia
  • Psamoma bodies
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18
Q

Describe the thyroid findings of Hashimoto’s thyroiditis

  • Gross:
  • Histology:
  • Cytology:
A
  • Gross:
    • Diffusely enlarged
  • Histology:
    • Lymphocytes and plasma celsl infitrate parenchyma
    • Atrophic follicles
  • Cytology:
    • Hurthle cells + heterogeneous lymphocytes
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19
Q

What is the classic histological finding of a follicular adenoma of the thyroid?

A

Normal-looking thyroid cells surrounded by a continous fibrous capsule

Note: FNA cannot distinguish between adenoma and carcinoma, but histologically, the carcinoma capsule will invade

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20
Q

What is the first line medication for anti-thyroid drug therapy?

Are there exceptions?

A

Methimazole

  • Use acutely to cool the pt down prior to radioiodine or surgery
  • Use long term for 12-18 months, then stop to assess remission

Exception = 1st trimester of pregnancy; use propylthiouracil (PTU) instead

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21
Q

List 3 substances that negatively regulate TRH secretion from the hypothalamus

A

Somatostatin

Dopamine

T3 (negative feedback)

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22
Q

What supplement may interfere with TSH, T3, T4 assays?

A

Biotin!

Will cause falsely low TSH, falsely high T3, T4

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23
Q

What etiology of hyperthyroidism will have bilateral increased iodine uptake?

A

Graves’ disease

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24
Q

What percentage of medullary thyroid carcinomas are hereditary?

What gene is likely mutated?

Which syndrome is associated?

A

20-25% are hereditary

RET proto-oncogene

  • MEN-2 (2A or 2B)
    • Association with mutations in
  • Also can just be familial tumors
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25
What (general) lab values are associated with subclinical hyperthyroidism? When should it be treated?
**Low TSH, normal free T3/T4** Treat if TSH \<0.1 to avoid atrial fibrillation, osteoporosis
26
What is the vertebral level of the thyroid?
C5 - T1
27
Which micronutrient is essential for the synthesis of thyroid hormone? What is the recommended daily allowance?
Iodine 150 mcg/day
28
What etiology of hyperthyroidism will have unilateral increased uptake?
Toxic _adenoma_ * The rest of the thyroid is trying to uptake less * This is a "hot nodule" = **less likely to be malignant**
29
Describe the clinical course of post-partum thyroiditis
Hyperhtyroid -\> Hypothyroid -\> Euthroid
30
Which cells of the thyroid secrete calcitonin?
C cells
31
Hurtle cells are associated with which thyroid pathology?
Hashimoto's thyroiditis
32
What is the first-line managment for Graves' opthalmopathy?
**Seleinum** Also: * Artificial tears * Avoid tobacco exposure * Even 2nd hand smoke * Teprotumumab * Monoclonal antibody that inhibits IGF-1 receptor; cross-reacts with TSH receptor?
33
Which enzyme converts T4 to reverse T3?
5 (mono)deiodinase | (DIO3)
34
What are the characteristics of a solid thyroid nodule on ultrasound? (3)
Many echo reflections Back wasll indistinct No acoustic enhancement
35
What are the (general) TSH and T4 levels in subclinical hypothyroidism? When should it be treated?
**High TSH** with **normal free T4** * Treat if TSH \> 10 (even if asymptomatic) * ALWAYS treat if TSH elevated in pregnancy * Ideally, pre-pregnancy
36
What is the most common malignant thyroid nodule?
**Papillary** thyroid carcinoma
37
Which enzyme converts T4 to T3?
5' (mono)deiodinase | (Either DIO1 or DIO2)
38
Describe the presentaiton of an anaplastic thyroid carcinoma What is the prognosis?
Suddenly enlarged neck Poor prognosis - usually extensive metastasis at time of presentation
39
What is the most common cause of hypothyroidism in the USA? Worldwide?
USA = **Hashimoto's thyroiditis** World = **Iodine deficiency**
40
When a thyroid problem is suspected, which lab should be checked first?
TSH *Then* check free T4 and total T3 (Don't want to only check T4/T3 and miss a central problem)
41
Why does thyroid gland move when we swallow or speak?
The thyroid gland is **attached to the tonge by the thyroglossal duct**
42
What percentage of thyroid noduels are benign?
90% (VAST majority are benign; many foudn incidentally)
43
Describe the signaling cascade activated when TSH binds to its receptor: * Gs: * Gq:
* **Gs**: * Activates **adenylyl cyclase** * Increase **cAMP** * Phosphorylation + activation of **PKA** * **Activation of targets in cytosol and nucleus** * **Gq**: * **IP3/CA2+** * Activates **PLC** * **Iodination, H2O2 production**
44
After a thyroid nodule is found on ultrasound, what is the next diagnostic step?
Fine needle aspiration if the ultrasound is concerning
45
Which genetic mutations are assoicated with papillary carcinoma of the thyroid?
**BRAF** RET
46
What is the classic histologic finding in follicular carcinoma of the thyroid?
Follicular celsl surrounded by a capsule - will see **capsular and vascular invasion** *Vs. follicular adenoma - caspule will be uniform and continuous*
47
What is the best management of a patient with newly dignosed Grave's disease?
Start **methimazole** (if not pregnant; PTU if 1st trimester) +/- propanolol, glucocorticoids * Re-evaluate in 3 weeks and discuss: * Continued medical therapy * Radioiodine ablation * Surgical ablation *Typically, pts are not thinking super clearly during Graves' presentation/exacerbation; cool them off first, then discuss long term management*
48
What are the characteristics of a thyroid cyst on ultrasound? (3)
Anechoic center Smooth black wall Acoustic enhancement
49
What is the main driver of the increase in incidence of thyroid nodules and thyroid cancer?
Increased ultrasound use
50
What is the imaging modality of choice for thyroid _function_?
**Iodine isotopes** *Use ultrasound for thyroid _structure_*
51
Does a "hot" thyroid nodule need to be biopsied?
No! Need to cool off nodule before biopsy Also, most hot nodules are benign
52
What is the most likely diagnosis of a patient with elevated free T4 and very low iodine uptake in the thyroid gland?
Thyroiditis * Thyroid gland is damaged * -\> Not working and **pre-stored thyroid hormone is spilling out into the system** * Will eventually get to a hypothyroid state
53
What are the symptoms of hypothyroidism? (6)
New symptoms of: * Menstrual irregularity * Infertility * Depression * Cognitive decline * Hyperlipidemia * Hair/skin changes * Nonspecific * Fatigue, weight gain, constipation
54
Antibodies against thyroglobulin and TPO are round in whihc thyroid pathology?
Hashimoto's thyroiditis
55
What are the indications for: * **123I scan:** * **131I scan:** * **99TcO4 scan:**
* **123I scan:** * Evaluate thyroid iodine uptake * Whole body scan; evaluate metastasis * **131I scan:** * **​**Ablate thyroid cells that uptake 131I via beta decay * **99TcO4 scan:** * Evaluate thyroid function
56
What is the functional unit of the thyroid?
Follicle
57
What is the treatment of choice for hypothyroidism?
Levothyroxine
58
What is coupling? (In the context of TH synthesis) What enzyme is responsible?
**Coupling via _TPO_** *Occurs after organification by TPO that results in MIT and DIT bound to thyroglobulin* * MIT and DIT are coupled to form T4 and T3 * T4 = DIT + DIT * T3 = MIT + DIT
59
Describe the pathophysiology of gestational thyrotoxiosis
**hCG** -\> **increase in thyroid hormone production** * Occurs in late 1st and early 2nd trimester, when hCG is high * hCG binds to TSH receptor * -\> **increased thyroid hormone production** * **-\> decreased TSH**
60
What is the embryologic tissue of origin of the thyroid?
Neuroectoderm (1st pharyngeal arch)

2021-2022 Endo Review Rearr. (19 decks)

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