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gi block > Endo: Thyroid Dysf > Flashcards

Endo: Thyroid Dysf Flashcards

1
Q

Which is the active form of thyroid hormone: T3 or T4?

Does most T3/4 exist free or bound to protein?

A

T3 is more active

Most T3/4 exists bound to protein

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2
Q

Name 2 causes of increased total T4/3

Name 2 causes of decreased total T4/3

A
  • Increased total T3/4
    • Hyperthyroidism
    • Increased binding proteins due to estrogen (OCP, pregnancy)
  • Decreased total T3/4
    • Hypothyroidism
    • Decreased binding proteins due to renal or liver disease
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3
Q

Name one cause of increased free T3/4

Name one cause of decreased free T3/4

A
  • Increased free T3/4 = hyperthyroidism
  • Decreased free T3/4 = hypothyroidism
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4
Q

What labs do we use to evaluate thyroid function? (3)

Which is most important?

A
  • TSH - most important
  • Free T4
  • Antibodies
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5
Q

Describe the results of a T3 Resin Uptake test

(assuming normal TBG levels)

A
  • When TBG is normal, amount of radiolabeled T3 taken up is indicative of TBG saturation
  • High T3RU (​a lot of radiolabeled T3 left on resin) indicates hyperthyroidism
  • Low T3RU (very little radiolabeled T3 left on resin) indicates hypothyroidism
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6
Q

What does it mean if Total T4 and T3RU go in opposite direction?

What about same direction?

A
  • Opposite direction Total T4 and T3RU indicates an abnormality in the amount of TBG
  • Same direction Total T4 and T3RU indicates a true thyroid hormone production problem
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7
Q

Symptoms of hyperthyroidism

  • Temperature
  • Weight
  • Skin/Hair (2)
  • Ocular (2)
  • GI (2)
  • MSK (1)
  • Neuro
  • CV (3)
A

Hyperthyroidism

  • Heat intolerance
  • Weight loss
  • Skin/Hair: warm skin, onycholysis
  • Ocular: exophthalmos (Grave’s), lid retraction
  • GI: Increased defecation, increased appetite
  • MSK: Osteoporosis
  • Neuro: anxious, restless, insomnia, tremors
  • CV: tachycardia, dyspnea, HTN
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8
Q

Compare overt and subclinical hyperthyroidism labs

A
  • Overt
    • low TSH
    • Elevated T3/4
  • Subclinical (can still have symptoms)
    • low TSH
    • T3/4 within normal
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9
Q

Define thyrotoxicosis

A

High level of T3/4 for any reason

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10
Q

What is the purpose of a iodine uptake scan?

A

Iodine uptake scans can be used together with a TSH level to determine whether the thyroid is responding appropriately to the TSH.

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11
Q

What is the use of thyroid uptake scans in patients with elevated T3/T4?

A

Thyroid uptake scan will differentiate hyperthyroidism from thyroiditis

  • Hyperthyroidism: elevated or normal iodine uptake (despite suppressed TSH)
  • Thyroiditis: low iodine uptake (appropriately responding to suppressed TSH)
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12
Q

Compare the overall cause of hyperthyroidism and thyroiditis.

A

Hyperthyroidism: Increased production of T3/4

Thyroiditis: Increased release of pre-formed T3/4 (due to inflammation or destruction)

*Both are forms of thyrotoxicosis (elevated T3/4)

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13
Q

Grave’s disease pathophys?

A

Grave’s Disease

  • Auto-antibodies against TSH receptor (TSI-IgG) continually stimulates TSH receptor on thyroid
  • Type II hypersensitivity
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14
Q

Tx of Hyperthyroidism (4)

A
  • Thyroid hormone synthesis inhibitors, beta blockers
  • Radioactive Iodine
    • Targeted killing of thyroid gland
  • Surgery
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15
Q

What is thyroiditis?

Explain its clinical course.

A
  • Thyroiditis = inflammation of thyroid leading to increased release of pre-formed T3/4
  • Timeline
    • High T3/4, low TSH for a few months
    • Once T3/4 stores are depleted, T3/4 is very low (thyroid is still sick and can’t produce hormones) and TSH becomes high
    • Healing and return to normal occurs a few months later (self-limited)
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16
Q

Compare the labs of overt and subclinical hypothyroidism

A
  • Overt
    • Elevated TSH
    • Low Free T4
  • Subclinical
    • Elevated TSH
    • Free T4 is within normal
17
Q

Symptoms of hypothyroidism

  • Temp
  • Weight
  • Skin/hair (3)
  • Ocular (1)
  • GI (2)
  • MSK (2)
  • Neuro (2)
  • CV (2)
A

Hypothyroidism

  • Cold intolerant
  • Weight gain
  • Skin/hair: Hair loss, dry cold skin, generalized edema
  • Ocular: periorbital edema
  • GI: Constipation, decreased appetite
  • MSK: carpal tunnel, myoedema
  • Neuro: lethargic, depression, decreased reflexes
  • CV: Bradicardia, exertional dyspnea
18
Q

Compare the lipid profiles in hyper and hypothyroidism

A

Hypothyroidism: Hypercholesterolemia

Hyperthyroidism: decreased LDL, HDL, total cholesterol

19
Q

Pathophysiology of Hashimoto’s Thyroiditis

A
  • Auto-Ab’s against thyroid cause thyroid damage, leading to insufficient T3/4 production
  • Ab’s against thyroid peroxidase or thyroglobulin
20
Q

What is the treatment for hypothyroidism?

When do we initiate tx?

A
  • Levothyroxine (synthetic T4)
  • If TSH above 10
21
Q

What is one thyroid emergency?

A

Myxedema coma: extreme form of hypothyroidism

Pt has bradycardia, hypothermia

22
Q

Name 4 symptoms that occur in both hyper and hypothyroidism

A
  • Fatigue
  • Proximal weakness
  • Menstrual changes and infertility
  • Decreased libido
23
Q

What is the most common cause of hyperthyroidism?

A

Grave’s disease

24
Q

Grave’s disease is associated with what genotypes?

A

Grave’s disease = HLA-DR3 and HLA-B8

25
Q

2 Unique symptoms of Grave’s disease

Why do these occur?

A
  • Pretibial myxedema due to dermal fibroblast activation
  • Exophthalmos due to T cell and fibroblast activation
26
Q

What genotype is assocaited with Hashimoto’s thyroiditis?

A

HLA-DR3

27
Q

Is the thyroid tender or non-tender in Hashimoto’s thyroiditis?

A

NON-tender

28
Q

What is postpartum thyroiditis?

How does it present?

Histology?

A
  • Self-limited thyroiditis following childbirth
  • Hypo or hyperthyroidism with painless thyroid
  • Histology: lymphocytic infiltrate
29
Q

What is Reidel thyroiditis?

Is it associated with hyper or hypothyroidism?

Describe palpation of the thyroid

A
  • Thyroid replaced by fibrous tissue with inflammatory cells
  • Causes hypothyroidism
  • Thyroid is a fixed, very hard, painless goiter
30
Q

What is de Quervain thyroiditis?

Histology? (1)

Findings? (3)

A
  • Self-limited hypothyroidism following viral infection
  • Granulomatous inflammation
  • Elevated ESR, jaw pain, painful thyroid (Quervain)

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