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Medicine > Hypothyroidism, Subacute Thyroiditis > Flashcards

Hypothyroidism, Subacute Thyroiditis Flashcards

1
Q

A disease state caused by insufficient circulating thyroid hormone

A

Hypothyroidism

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2
Q

Thyroid hormone deficiency caused by thyroid gland destruction or dysfunction

A

Primary hypothyroidism

Ex: Hashimoto’s thyroiditis

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3
Q

Most common cause of hypothyroidism

A

Hashimoto’s thyroiditis

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4
Q

Thyroid hormone deficiency caused by pituitary insufficiency
TSH deficiency occurs in the context of other anterior pituitary hormone deficiencies
Isolated TSH deficiency is rare

A

Secondary hypothyroidism

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5
Q

Thyroid hormone deficiency caused by hypothalamic disease or disruption of hypothalamic pituitary portal blood flow
TRH deficiency usually occurs in the context of other hypothalamic hormone deficiencies
Isolated TRH deficiency is very rare

A

Tertiary hypothyroidism

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6
Q

Elevated serum TSH

Normal free T4

A

Subclinical hypothyroidism

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7
Q

Autoimmune Hashimoto’s thyroiditis
Epidemiology

Incidence
Mean age
Sex

Risk

Other predisposing factors

A

W 400: 100,000
M 100: 100,000

60 years
Prevalance increases with age

Rarely seen in children

Common in Japanese
High iodine diet

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8
Q

Most common cause worldwide of hypothyroidism

A

Iodine deficiency

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9
Q

Most common cause of hypothyroidism in iodine-sufficient regions

A

Autoimmune Hashimoto’s Thyroiditis

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10
Q

Autoimmune disorder with genetic and environmental susceptibilities

Characterized by marked lymphochytic infiltration
atrophy of the thyroid follicles
absence of colloid
fibrosis

Leading to thyroid gland destruction

A

Hashimoto’s thyroiditis

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11
Q

Thyroid-cell destruction is believed to be primarily mediated by

A

CD8+ cytotoxic T cells

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12
Q

CD8 cytotoxic t cells destroy their targets by

A

Perforin induced cell necrosis

Granzyme B-induced apoptosis

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13
Q

Thyroid cells are rendered susceptible to apoptosis because of cytokines

A

IL - 1
TNF
IFN

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14
Q

End stage of Hashimoto’s thyroiditis

More extensive fibrosis
Less pronounced lymphocytic infiltration
Absence of thyroid follicles

A

Atrophic thyroiditis

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15
Q

Primary Hypothyroidism etiology

A 
Surgical: thyroidectomy
Radiation for iodine treatment in hyperthyroidism
External radiation of neck for lymphoma
Drugs 
Congenital
Infiltrative disorders
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16
Q

Congenital causes of Primary Hypothyroidism

A

Thyroid agenesis or dysgenesis
Dyshormogenesis
TSH receptor mutations (inactivating)
Maternal antithyroid hormone therapy (transient)
Maternal TSH receptor antibodies (treatment)

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17
Q

Drugs that cause hypothyroidism

A

Amiodarone
Lithium
Antithyroid drugs
Interferon alpha

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18
Q

Cause of transient hypothyroidism

A

Silent thyroiditis (postpartum thyroiditis)
Subacute thyroiditis
Shortly after iodine treatment or subtotal thyroidectomy for Grave’s disease

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19
Q

Hypothyroidism symptoms and signs

A 
Fatigue
Generalized weakness
Dry skin
Cold intolerance
Hair loss
Difficulty concentrating/poor memory 
Constipation
Weight gain with poor apetite
Dyspnea
Hoarse voice
Menorrhagia (later in the clinical course, oligo or ameno)
Paresthesia
Impaired hearing
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20
Q

Signs of hypothyroidism

A 
Dry coarse skin; cool peripheral extremities
Puffy face, hands, feet (myxedema)
Diffuse alopecia
Bradycardia
Nonpitting peripheral edema
Delayed tendon reflex relaxation
Carpal tunnel syndrome
Serious cavity effusions
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21
Q

Most common symptom of hypothyroidism

A

Fatigue and generalized weakness

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22
Q

Most common sign of hypothyroidism

A

Dry, coarse skin, cool peripheral extremities

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23
Q

Laboratory manifestations of hypothyroidism

A 
Normochromic, normocytic anemia
Hypercholesterolemia
Hyponatremia (in advanced hypothyroidism)
Hyperprolactinemia
Elevated creatine phosphokinase level
Hypoglycemia (myxedema coma)
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24
Q

The first-line diagnostic test for hypothyroidism and patient screening

A

Serum thyrotropin TSH

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25
Q

An elevated TSH level should be confirmed by

A

repeated measurement of TSH with FT4

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26
Q

When evaluating thyroid function in suspected hypothalamic/pituitary disease, TSH measurement

A

is inadequate

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27
Q

May be useful to define underlying cause of primary hypothyroidism although not required in all settings

A

measurement of antithyroid antibodies

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28
Q

If a patient has sustained hypothyroidism after extensive exclusion of other potential causes, it is presumed to be

A

autoimmune in origin

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29
Q

Primary hypothyroidism Initial Test

A

TSH

If normal, exclude primary thyroid abnormality
If elevated, confirm by repeat TSH and FT4

30
Q

Primary hypothyroidism thyroid function profile

A

Elevated TSH

Low FT4

31
Q

Subclinical hypothyroidism

A

Elevated TSH

Normal FT4

32
Q

TSH normal and pituitary disease suspected but

low free T4 level

A

assess for possibility of medication effects or sick euthyroid syndrome

33
Q

TSH level normal and pituitary disease suspected

Normal free T4

A

Excludes secondary and tertiary causes of hypothyroidism

34
Q

Secondary or Tertiary Hypothyroidism Lab profile

A

TSH level: highly variable usually normal

FT4: LOW

35
Q

Present in 90-95% of patients with autoimmune hypothyroidism
40-80% of patients with Grave’s
Useful in predicting progression of subclinical to overt hypothyroidism

A

TPO antibodies

36
Q

Present in 5-25% of euthyroid women
2% of euthyroid men

Not specific for diagnosis of autoimmune hypothyroidism not indicated for evaluation

Important in management of patients with differentiated thyroid carcinoma

A

Thyroglobulin autoantibodies

37
Q

Iodine scan in Hashimoto’s thyroiditis shows

A

Decreased and heterogenous tracer uptake

38
Q

When secondary or tertiary hypothyroidism is suspected, this imaging may be employed

A

MRI of pituitary gland

MRI/CT of the brain if suprasellar process suspected

39
Q

Biopsy of Hashimoto’s thyroiditis reveal

A

Lymphocytic infiltration
Follicular destruction
Fibrosis

40
Q

Treatment of choice for hypothyroidism

A

Levothroxine

41
Q

Endocrine emergency treated promptly with thyroid hormone once coexisting adrenal insufficiency is excluded

A

Myxedema coma

42
Q

Treatment for overt hypothyroidism

A

Levothyroxine 1.6 microgram/kg

Starting dose
<60: without CV disease 50-100
in severe: lower end dose recommended

43
Q

TSH should be checked once started on levothyroxine after

A

2 months

44
Q

Goal of TSH level in hypothyroidism

A

1-2 mIU/L

45
Q

Multiple levothyroxine products exist.

TSH level should be rechecked after switching to a new product to ensure adequate dosing.

A

Bioequivalence

46
Q

In a patient of normal body weight taking >200 ug of levothyroxine with elevated TSH and normal or high FT4 may indicate

A

poor compliance

47
Q

Patients who miss doses can be advised to take up to

A

3 doses of skipped tablets at once owing to long half life

48
Q

In patients with TSH >4.5 mU/L and positive TPO antibodies

Subclinical hypothyroidism

Patient may be started on

A

Levothyroxine

If not started, monitor TSH anually

49
Q

Levothyroxine treatment on Subclinical Hypothyroidism may improve

A

Left ventricle function

Lipid profile

50
Q

In patients with history or high risk hypothyroidism who are contemplating pregnancy, they must be rendered

A

euthyroid before and throughout pregnancy

51
Q

Thyroid function of pregnant patients should be evaluated once

A

Pregnancy confirmed

2nd and 3rd trimester

52
Q

Levothyroxine doses often need to be increased by how much in pregnancy

A

> /= 30-50%

The dose may be returned to preconception levels postpartum

53
Q

In elderly persons, dose of thyroxine may be lessened by

A

20%

If with CAD, starting dose is 12.5-25 ug/d with similar increments every 2 months until TSH is normalized

54
Q

Minor complications of surgery for hypothyroidism

A 
Intraoperative hypotension
Sensitivity to anesthesia
Ileus
Hyponatremia
Central nervous dysfunction
55
Q

Drugs that interfere with thyroid hormone absorption

A 
Iron
Calcium carbonate
Cholestyramine
Aluminum hydroxide gel
Sucralfate
Dietary soy
56
Q

Medical conditions that may interfere with thyroid hormone absorption

A

GI maladaptive disorders

Previous small-bowel bypass surgery

57
Q

Postmenopausal hormone therapy requires increase in levothyroxine by

A

35%

58
Q

Myxedema coma treatment

A

Levothyroxine 500 ug

T3 IV (conversion of T3 to T4 is impaired)

Combined levothroxine and T3 as single initial bolus

Daily doses of levothyroxine and T3

59
Q

Excess T3 may provoke

A

arrhythmia

60
Q

Supportive measures for myxedema

A

Treatment of precipitating factor
Ventilatory support during first 48 hours
Parenteral hydrocortisone (50 mg q6) is indicted for impaired adrenal reserve
Hypertonic saline or intravenous glucose for severe hyponatremia or hypoglycemia
Hypotonic IV avoided
External warming if temperature <30 to avoid cardiovascular collapse
Drug clearance may be impaired
Sedatives should be avoided if possible

61
Q

Complications associated with untreated hypothyroidism

A 
Increased sensitivity to sedatives, analgesics and anesthetic agents
Hypercholesterolemia 
CAD
Diastolic dysfunction and hypertension
Decreased sensitivty to warfarin
62
Q

Painful inflammation of thyroid gland
Self-limited

Transient hyperthyroidism -> hypothyroidism -> euthyroid in a span of

A 
Subacute thyroiditis
De Quervain’s thyroiditis
Granulomatous thyroiditis
Giant cell thyroiditis
Viral thyroiditis
63
Q

Subacute thyroiditis epidemiology

Age

Sex

Season

A

peaks 30-50 years

Women 3x

Peaks in summer

64
Q

Patients with subacute thyroiditis often report with

A

antecedent viral respiratory infection

65
Q

Subacute thyroiditis predominant HLA

A

HLA B35

66
Q

Viruses implicated in Subacute Thyroiditis

A 
Mumps
Measles
Influenza
Coxsackie
Adenovirus
Echovirus
67
Q

Painful, mildly enlarged thyroid
Asymmetric
Sore throat with pain to the jaw or ear
Rare cause of chest pain

Acute onset of hyperthyroidism

Fever
Fatigue
Myalgia

A

Subacute thyroiditis

68
Q

Thyrotoxic phase of Subacute Thyroiditis

A

T4, T3 increased

Low TSH

69
Q

Ratio of T4 and T3 in Subacute Thyroiditis

A

T3>T4

Inc T4/T3 ratio

70
Q

Hypothyroid phase of Subacute Thyroiditis

A

Moderately inc TSH
Low T4,T3

after several weeks thyroid is depleted of stored thyroid hormone

71
Q

Subacute Thyroiditis

Dx

Tx

A

Radioiodine uptake and scan to assess

UTZ, FNAB not needed

Symptomatic control of thyroid pain and tenderness and non-specific symptoms
Mitigating the transient effects of hyperthyroidism

72
Q

Thyroid cancer associated with Hashimoto’s

A

Primary thyroid lymphoma

Medicine (29 decks)

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