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Endocrine > Thyroid Disorders > Flashcards

Thyroid Disorders Flashcards

1
Q

What thyroid disorders are in your differential if you notice high T3/T4?

A

Hyperthyroidism
Thyrotoxicosis
Thyroid storm

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2
Q

What thyroid disorders are in your differential if you notice low T3/T4?

A

Hypothyroidism

Myxedema

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3
Q

Once free from the thyroid, the majority of T3-T4 circulates the body bound to which protein?

A

99% are bound to thyroid binding globulin (TBG) and albumen.

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4
Q

Where is TBG produced?

A

In the liver

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5
Q

Which thyroid hormone is most prevalent?

A

T4 (T3 is 3-8 times more potent)

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6
Q

What is the daily iodine requirement?

A

500 mcg/day

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7
Q

What can excess iodine cause?

A

hypothyroidism and thyroid nodules

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8
Q

What hormones are produced in the hypothalmus?

A

thyroid releasing hormone (TRH)

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9
Q

What hormones are produced in the pituitary?

A

thyroid stimulating hormone (TSH)

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10
Q

What hormones are produced in the thyroid gland?

A

Thyroxine (T4) and Tri-iodo-thyro-nine (T3)

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11
Q

Describe the positive feedback loop for the stimulation of thyroid hormone secretion.

A
  1. TRH is secreted by the hypothalmus
  2. TRH stimulates TSH secretion by the pituitary gland
  3. TSH stimulated TH secretion by the thyroid gland
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12
Q

Describe the negative feedback loop for the regulation of thyroid hormone secretion.

A
  1. TH inhibits TRH secretion
  2. TRH inhibition inhibits TSH secretion
  3. TSH inhibition reduces TH secretion
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13
Q

How does iodine deficiency result in a goiter?

A
  1. Without iodine, TH cannot be synthesized from its precursors.
  2. The absence of TH promotes TRH secretion
  3. This stimulates TSH secretion
  4. This stimulates synthesis of TH precursors which accumulate and enlarge the thyroid.
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14
Q

What are the characteristics of a patient with hypothyroidism?

A

Dry brittle hair with loss; edema of the face and eyelids; skin is pale,, dry and rough; cold intolerance; bradycardia; weight gain; constipation; delayed DTR

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15
Q

What do we expect to see on labs in a patient with hypothyroidism?

A

T4 and radioactive iodine uptake is low.

TSH is elevated in primary and decreased in secondary.

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16
Q

How is hypothyroidism treated?

A

T4- Levothyroxine

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17
Q

What are the essentials of diagnosis for thyroiditis?

A

Swelling of the thyroid gland sometimes causing pressure symptoms in acute and sub acute forms; painless enlargement and rubbery firmness in chronic form.

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18
Q

What is the most common cause of hypothyroidism?

A

Hashimotos

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19
Q

What are the clinical features to Hashimotos Thyroiditis?

A

Thyroid is initually diffusely enlarged, firm and finely nodular.
Pain and tenderness are not usually present.

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20
Q

What is the etiology of Hashimotos?

A

Results from abnormal T cell activation and subsequent B cell stimulation to secrete a variety of auto antibodies. (TgAb and TPOAb)

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21
Q

What is sub acute thyroiditis?

A

De Quervian thyroiditis- typically presents as a moderatley enlarged, tender thyroid with hyperthyroidism, often with dysphagia. Often follows an URI and its incidence peaks in summer.

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22
Q

What is the treatment of choice for sub acute thyroiditis?

A

asprin, which relieves pain and inflammation

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23
Q

What is suppurative thyroiditis?

A

Caused by infection of the thyroid gland, usually bacterial.

(rare since the thyroid is resistant to infection due to high iodine content and good blood supply)

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24
Q

What are the clinical features of suppurative thyroiditis?

A

Patients are typically afebrile with severe pain, tenderness, redness and fluctuation in the region of the thyroid gland.

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25
Q

What is the treatment of choice for suppurative thyroiditis?

A

Appropriate antibiotics

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26
Q

What disease presents with a thinning of the outer halves of the eyebrows?

A

Hypothyroidism

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27
Q

What are the symptoms of myxedema?

A

Puffiness of the face and eyelids; hard pitting edema; effusions to the pleural, peritoneal and pericardial cavities; cardiac enlargement “myxedema heart”; bradycardia

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28
Q

How do we treat a patient presenting with myxedema coma?

A
  1. Provide steroids, tapering them off
  2. Do random cortisol checks
  3. Start T4 replacement, thyroxine bolus (IV)
  4. IV fluids/Warming blankets
29
Q

What is hyperthyroidism/thyrotoxicosis?

A

Serum TSH levels are supressed, T3 and T4 are elevated.

30
Q

What are the essentials of diagnosis for hyperthyroidism?

A

sweating; weight loss; loose stools; heat intolerance; irritability; tachycardia; warm moist skin; stare; tremor

31
Q

What is the most common cause of thyrotoxicosis?

A

Graves Disease

32
Q

What are common findings in a patient with Graves Disease?

A

Goiter, Exopthalmos, and marked skin thickening

33
Q

What causes exopthalmos in hyperthyroidism?

A

Adipose tissue is increased due to inflammation and accumulation of hydrophilic glycosamino-glycans (GAG)

Increase in GAG creates an increase in osmotic pressure in the orbit.

34
Q

What else does GAG cause with hyperthyroidism?

A

Due accumulation in the dermis of (GAG), secreted by fibroblasts there is a marked skin thickening (least common manifestation of Graves’)

35
Q

What is likely to be the presenting feature of hyperthyroidism?

A

Atrial fibrillation may be the presenting manifestation of hyperthyroidism and may precipitate heart failure..

36
Q

How do we diagnose hyperthyroidsim?

A
  • If low TSH and elevated ft4/t3

- May need to get thyroid US

37
Q

What is the treatment for hyperthyroidism?

A
  • PTU decreases Thyroid hormone synthesis

- Methimazole and PTU decrease release of thyroid hormone and peripheral conversion T4 to T3

38
Q

What is the key antibody patients with Graves Dz have?

A

TSH- receptor stimulating antibody

39
Q

What are Toxic Adenoma & Multinodular Goiter?

A

Common causes of hyperthyroidism, second in prevalence only to Graves’ disease.

About 95% of thyroid nodules are benign.

40
Q

What is the clinical picture of a patient with a toxic adenoma?

A

The classic clinical picture is a hyperthyroid patient with a palpable thyroid nodule that corresponds to an area of increased radioiodine concentration on thyroid scan.

41
Q

How does a patient with a Toxic Multinodular Goiter present?

A

Typically presents with one or more focal areas of increased radioiodine uptake.

42
Q

What are the clinical features of a patient with thyroid storm?

A

marked delirium, severe tachycardia, vomiting, diarrhea, dehydration, and, in many cases, very high fever.

43
Q

What is the treatment for thyroid storm?

A
  • Admit to ICU
  • IV fluids/cooling measures
  • Monitor for lytes/BP and temp
  • Hydrocortisone
44
Q

What are the essentials of diagnosis for a patient with thyroid cancer?

A
  • Painless swelling in region of thyroid.
  • Thyroid function tests usually normal.
  • Positive thyroid needle aspiration
45
Q

How do we diagnose thyroid cancer?

A
  • If you feel a firm nodule…REFER

- Can order an US but fine needle biopsy is required

46
Q

What is the most common type of thyroid cancer? Which has the worst prognosis?

A

Papillary; Anaplastic- 5% but a mortality of 98%

47
Q

What are the risk factors for thyroid cancer?

A

History of thyroid cancer in one or more first degree relatives
History of external beam radiation as a child
Exposure to ionizing radiation in childhood or adolescence
Prior hemithyroidectomy with discovery of thyroid cancer
18FDG avidity on PET scanning
MEN2/FMTC-associated RET proto-oncogene mutation
Calcitonin >100 pg/mL.
MEN, multiple endocrine neoplasia
FMTC, familial medullary thyroid cancer.

48
Q

How do we treat thyroid cancer?

A

U/S guided FNA

Total Thyroidectomy

49
Q

What is the cause of hypothyroidism?

A

May be due to the failure or resection of the tyroid gland itself or deficiency of pituitary TSH.

50
Q

What is the single best test for hypothyroidism?

A

TSH; it is increased with primary hypothyroidism, but low or normal with hypopituitarism

51
Q

What is a complication in therapy for hypothyroidism?

A

Pre-existent coronary artery disease and heart failure may be exacerbated by levo-thyroxine therapy.

52
Q

If a patient with hypothyroidism presents with hypothermia how do we treat?

A

Warm only with blankets since faster warming can precipitate cardiovascular collapse

53
Q

What is the pathogenesis of Graves Disease?

A

Involves the formation of auto-antibodies that bind to the TSH receptor in the thyroid cell membranes and stimulate the gland to hyperfunction. Such antibodies are called thyroid stimulating immunoglobulins (TSI) or TSH receptor antibodies.

54
Q

What it the treatment for hyperthyroidism?

A 
propranolol (initial treatment of choice in thyroid storm)
thiourea drugs (PTU and methimazole)- PTU IF PREGO!
radioactive iodine (destroys overactive thyroid tissue)
Thyroid surgery (thyroidectomy)
55
Q

What is myxedema?

A

A nonpitting fluid retention state due to mucopolysaccharide buildup. It most commonly occurs in the periorbital area.

56
Q

What is the hallmark of myxedema coma/crisis?

A

altered mental status

57
Q

What is the most common cause of suppurative thyroiditis?

A

S. aureus

58
Q

How do we diagnose suppurative thyroiditis?

A

fine needle biopsy is required and gram stain culture

59
Q

What is the most common cause of a painful thyroid?

A

Sub acute thyroidits

60
Q

What is fibrous thyroiditis?

A

Riedel thyroiditis, dense fibrous tissue in the thyroid gland. An asymmetric, hard, “woody”, thyroid may be palpated.

Diagnosis is made by biopsy

Treatment: may respond to long-term tamoxifen treatment

61
Q

What is a nontoxic goiter?

A

a slowly enlarging thyroid gland over years, that usually is asymptomatic unless impinging or causing thoracic inlet obstruction. Multiple painless nodules are palpable.

62
Q

What is a solitary thyroid nodule?

A

Thyroid adenoma is the most common, it is asymptomatic.

63
Q

How can we differentiate a solitary thyroid nodule from a multinodular goiter?

A

the nodule of the adenoma is encapsulated, but the nodules of the multi nodular goiters are not.

64
Q

What is the most common type of a solitary thyroid nodule?

A

follicular adenoma

65
Q

What is the most sensitive test to detect thyroid lesions?

A

US

66
Q

When should we be concerned of malignancy of the thyroid?

A

In the presence of irregular or indistinct margins, heterogeneous echogenicity, intra-nodular vascular margins, micro-calcifications, complex cyst patterns, or a size > 1 cm

67
Q

What is the most common type of thyroid cancer?

A

papillary

68
Q

What is the presentation of thyroid cancer?

A

painless neck swelling and a palpable, single firm nodule is the most common presentation

69
Q

What is the treatment for thyroid cancer?

A

surgical resection is indicated and patients are required to be on T4 replacement therapy for life.

Endocrine (8 decks)

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