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Endocrine > 178. Thyroid Pathophysiology, Nodules, Cancer > Flashcards

178. Thyroid Pathophysiology, Nodules, Cancer Flashcards

1
Q

Lab sign for hypothyroidism

3 types of primary hypothyroidism

Best single test to evaluate thyroid fx

Tx for hypothyroidism

A

Labs: HIGH TSH, LOW T3/T4

  1. autoimmune destruction (Hashimoto’s) - #1 cause in iodine-sufficient population
  2. Iodine Deficiency - #1 cause worldwide
  3. Radiation-Induced (from lymphoma or head/neck cancer tx)

TSH test - best single test to evaluate thyroid fx

Tx: Levothyroxine (LT4) - gets converted to T3 in peripheral tissues - goal to NORMALIZE TSH

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2
Q

Hashimoto’s Thyroiditis

  • what is it
  • US finding
  • sx

Subclinical Thyroiditis

  • labs
  • when to treat
A

H: overt hypothyroidism (high TSH, low T3/T4) due to autoimmune destruction (TPO Ab’s)
US: heterogeneous (hypoechoic) echotexture - feels squishy/bacillated
Sx: nonspecific - fatigue, weight gain, constipation, hair skin changes
new menstrual irregularities, new depression, unexplained infertility, cognitive decline, +FamHx of autoimmune disease, hyperlipidemia

Subclinical: high TSH but normal T3/T4 (repeat in 1 month to show consistent TSH elevation)

Treat TSH when
TSH > 10
TSH > 7 and age >65
TSH elevated in pregnancy

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3
Q

Thyrotoxicosis

  • what is it
  • labs (which are best?)
  • signs/sx (PE)
A

Too much T3/T4 without specific etiology
Labs: LOW TSH, high T3/T4 (best labs: TSH > fT4/total T3)
Signs: weight loss (despite increased appetite), heat intolerance (always cold), hyperactivity, fatigue, irritability, anxiety, tremor, insomnia, menstrual disturbances, SoB, palpiations, pelvic/pectoral girdle muscle weakness, eye pain (graves)
Sx: tachycardia, wide pulse pressure, systolic HTN, dynamic precordium, brisk reflexes, tremor of outstretched hand, nodular/large/tender/bruits on thyroid, eyes (lid lag/stare/proptosis/EOMI restriction)
skin (warm, infiltrative dermopathy - raised hyperpigmented violaceous papules)

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4
Q

Graves’ Disease

  • what is it
  • US
  • Scintigraphy
  • Difference in eye sx b/w any thyrotoxicosis and graves’ opthalmopathy (tx for eyes too)
  • tx
A

TRAb mediated activation of TSHR (TSI, TBII, TRAb)
US: “thyroid inferno” diffuse increased vascularity; prominent extrathyroid vessles, more heterogeneous echotexture
Scintigraphy: diffuse increased homogenous I uptake

Eye: any cause hyperthyroid (lid lag, retraction, stare due to increased SNS tone)
Graves (Proptosis, diplopia, CN2 involvement, inflammatory changes - conjunctival injection, periorbital edema, chemosis)
Tx: selenium (decrease eye sx), artificial tears, avoid tobacco (worsens eye sx), teprotumumab (inhibits IGFR - next to TSHR - colocates in eye)

TX

  1. Meds: B-blockers (reduce SNS tone), Methimazole (first line, used for 12-18 months, SE: rash, urticaria, pruritis, fever, GI, major - AGRANULOCYTOSIS (low WBC need monitor CBC), contraindicated in 1st trimester pregnancy), PTU (SE: severe liver injury - fulminant hepatitis, used only during first trimester of pregnancy - safer than methimazole)
  2. Radioiodine: can cure but destroys thyroid (B particles) and may worsen Graves’ eye disease (need lifelong hormone tx)
  3. Surgery - total thyroidectomy - for pts with large goiters/compressive sx (poor venous flow, dysphagia), pregnant women, pre-pregnancy, SE to MMI
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5
Q

Toxic Adenoma/Multinodular Goiter

  • what is it
  • scintigraphy: adenoma vs. MNG
A

Autonomously functioning thyroid tissue
Adenoma: “hot nodule” of increased focal uptake, tx with 131-I at time of scan (radioablation), need US to look for other non-fx nodules
MNG: multi-focal increased uptake - need to confirm nodules on US

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6
Q

What is the effect of biotin on thyroid labs?

A

Biotin - hair/nail supplement
Cause falsely LOW levels of TSH; falsely HIGH levels of T3, T4, TSI, TRAb (lead to graves’ misdx)
dietary biotin: blocks biotinylated capture mAbs of immunoassay to bind TSH

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7
Q

Thyroiditis

  • what is it
  • course of disease state
  • post-partum thyroiditis (tx)
  • gestational thyrotoxicosis (cause, when, tx)
A

Damage to thyroid gland = leakage of stored thyroid hormone = thyrotoxicosis (for 6-8 weeks until stores deplete)
Course: hyperthyroid phase -> normal -> hypothyroid phase (depleted hormones) -> restoration of normal

Post-partum: hyperthyroid from 0-3months after (tx: B-blockers)
hypothyroid from 3-6months after (tx: levothyroxine)

Gestational: hCG-mediated increase in T3/T4 production in late 1st/early 2nd trimester of pregnancy
sx: NO GOITER, TRAb Negative!, may cause suppressed TSH +/- high free T4 and hyperemesis gravidarum
High HCG suppresses TSH and high TSH suppresses HCG due to sharing common alpha-subunit (also LH/FSH)
tx: sx will resolve as hCG decreases

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8
Q

Subclinical Hyperthyroidism

  • labs
  • sx
  • when to tx
A

Labs: low TSH and normal fT4/T3
sx: cardiac - increased risk of AFIB
bone - increased risk of osteoporosis (lower BMD, higher fracture risk) - reversible if hyperthyroidism collected

Tx: When TSH < 0.1 or low with more RFs (higher age, osteoporosis)

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9
Q

Thyroid Adenoma

  • what is it
  • composition
  • evaluation: high suspicion US pattern, which US nodules are benign, when should US findings indicate biopsy, FNA biopsy, mLc testing
A

Most common thyroid nodule (benign solitary neoplastic nodule of follicular/Hurthle cells)
Only biopsy with low-medium suspicion of malignancy from US
High sus US: microcalcifications, shape taller than wide, irregular margins, extrathyroidal extension, interrupted rim calcification with soft tissue extrusion = 70-90% chance of malignancy!!
Hypoechoic worse (more malignant) than hyperechoic
Benign US: pure cystic nodule

FNA Biopsy: Bethesda system reports malignancy risk and recommends surgery (if indeterminate - rely on US and mLc markers)

mLc testing: inform mgmt of indeterminant nodules, best used as rule-out test (high sensitivity/NPV), certain mutations are highly predictive of malignancy (BRAF, TERT promoter)

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10
Q

Papillary Carcinoma

  • what is it
  • prevalence
  • histo
A

most common malignant thyroid tumor (80%)
well-differentiated, multifocal, with lymphatic spread (but GOOD prognosis)

Histo: papillae with vascular core, optically clear nuclei, nuclear grooves + pseudoinclusions, rare/absent mitoses, psammoma bodies (calcifications)

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11
Q

Follicular Carcinoma

  • prevalence
  • types
  • tx
A

18% malignant tumors
Minimally Invasive - vascular or capsular invasion (better prognosis)
Widely Invasive - more extensive invasion into surrounding muscles, vessels, trachea, etc. (need lots of tx/interventions)

Tx:

  1. Lobectomy or Total Thyroidectomy (depends on size)
  2. Post-Op US and TG - look for tumor markers
  3. Reactive Iodine Tx - thyroid remnant ablation + microscopic mets
  4. Levothyroxine for TSH suppression
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12
Q

What is the purpose of TSH suppression tx? what are the consequences of TSH suppression?

A

High TSH may trigger growth of malignant thyroid tissue
Low risk cancer hx - keep TSH <0.5
High risk cancer hx - keep TSH <0.1
Normal (0.4 - 4.0)

consequences of TSH suppression
- higher risk of AFib
- aggravation of postmenopausal osteoporosis
- more signs/sx of thyrotoxicosis
(best therapy for low risk patients)
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13
Q

What is the long-term mgmt of thyroid cancer?

A

Dynamic risk stratification based on initial staging and ATA risk

  • US monitoring
  • TG and TG-Ab surveillance
  • role for Iodine scans, PET scans, CT in advanced thyroid cancer
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14
Q

Anaplastic Carcinoma

  • pt population
  • prognosis
  • gross
  • three histo patterns
A

Pt: older age
Prognosis: poor survival (worst prognosis)
Gross: rapidly growing mass
Histo Patterns: (all with necrosis + hemorrhage)
1. Spindle Cells
2. Giant Cells
3. Squamoid Cells

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15
Q

Medullary Thyroid Cancer (MTC)

  • what is it
  • markers
  • prevalence
  • etiology
  • types of etiology
  • dx
  • tx
A

Neuroendocrine tumor of parafollicular C cells
Produce calcitonin + CEA
2% all thyroid ca (rare)
75% sporadic (unilateral), 25% hereditary due to MEN2 (bilateral)
MEN2: AD disorder, mutation in RET proto-oncogene
MEN2A: MTC, PCC, hyperparathyroidism (primary causes high Ca)
MEN2B: MTC, PCC, Ganglioneuromas, Marfanoid habitus

Dx: FNA biopsy, calcitonin level, mapping LN with US and CT, staging with CT of lungs and abdomen

if MTC established, screen for PCC (measure metanephrine), determine serum Ca+PTH if hyperparathyroidism possible, RET gene analysis

Tx:
Surgery - total thyroidectomy, central neck dissection/modified radial neck dissection (50% have LN mets)
MEN2 - preclinical prophylactic total thyroidectomy (before MTC presents)
Surveillance - measure calcitonin and CEA; follow-up imaging - neck US, CT of met disease if indicated

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16
Q

Thyroid Lymphoma

  • what is it
  • gross
  • ddx
  • dx

Metastatic
- prognosis

A

TL: arise in long-standing autoimmune (Hashimoto’s) thyroiditis

  • large fleshy masses - rare + rapidly growing
  • ddx: anaplastic carcinoma of thyroid
  • usually B cell lymphoma
  • immunophenotyping performed on FNA biopsy (for dx)

Metastatic Tumors: can locate in thyroid - POOR PROGNOSTIC SIGN

Endocrine (23 decks)

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