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Chemistry > Thyriod Function > Flashcards

Thyriod Function Flashcards

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1
Q

Thyroid General Info

A

Held around trachea loosely by connective tissue
3-5 cm long
15-25 g

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2
Q

Thyroid Gland Microscopic Info

A

2 types of cells
- Follicular cells
- Parafollicular cells

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3
Q

Follicular Cells

A

AKA fundamental unity of the thyroid gland
Produces thyroglobulin (glycoprotein) secreted into the interior of follicle
Site of production of thyroid hormones

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4
Q

Parafollicular Cells

A

AKA C-Cells
Secrete calcitonin

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5
Q

Calcitonin

A

Protein involved in metabolism of Calcium and Phosphorus

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6
Q

Physiological Effects of Thyroid Hormones

A

Calorigenic
Support growth, development, sexual & CNS maturation
Increase Protein synthesis
Increase heart rate and GI tract motility
Increase Sensitivity of cell receptors to catecholamines

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7
Q

Organs Unaffected by Thyroid Hormones

A

Brain
Retina
Lungs
Spleen
Testes

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8
Q

Calorigenic

A

Increase O2 consumption and metabolic rate

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9
Q

Source of Iodide

A

Dietary
Trapped from the circulation

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10
Q

Iodide Oxidized

A

Inside Follicle
Attaches to tyrosine residue of thyroglobulin

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11
Q

MIT

A

Monoiodotyrosine

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12
Q

DIT

A

Diiodotyrosine

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13
Q

Iodination of Thyroid Hormones

A

Synthesis is under action of thyroid peroxidase (TYR) and thyroid stimulating hormone (TSH)

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14
Q

T3

A

Made when MIT and DIT are combined

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15
Q

T4

A

Made when 2 DITs are combined

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16
Q

Colloid

A

Located in Follicular
Stores thyroid hormones

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17
Q

Negative Feedback for T3 & T4

A

Stimulation of the pituitary
Peptide bonds between tyrosine and thryoglobulin are cleaved by thyroglobulin proteases

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18
Q

Thyroxine (T4)

A

Major Hormone (10X T3)
Deiodinated to T3 in peripheral tissue (liver)
Less biologically active than T3

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19
Q

Triiodothyronine (T3)

A

Produced in less concentration than T4
More biologically active (3-5X T4)

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20
Q

Reverse T3 (rT3)

A

Formed from deiodination of T4
Not biologically active

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21
Q
A

T4

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22
Q
A

T3

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23
Q
A

rT3

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24
Q

Transport of Thyroid Hormones

A

Circulate bound to proteins
Free form is physiologically active form

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25
Q

TBG

A

Thyroid Binding globulins

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26
Q

Albumin

A

Catch all carrier protein

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27
Q

Free T4

A

fT4
0.03%

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28
Q

Free T3

A

fT3
0.3%

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29
Q

Bound T4

A

99.97%

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30
Q

Bound T3

A

99.7%

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31
Q

Testing for Thyroid

A

Competitive binding immunoassay
Stripping agent is added to remove TBG and other binding proteins

32
Q

Thyroid Antibodies

A

Previously thyroid microsomal antibodies
Hashimoto’s Thyroiditis - 80-99%
Grave’s Disease - 45-80%

33
Q

Antithyroglobulin Antibodies

A

Hashimoto’s thyroiditis - 6-60%
Grave’s Disease 70-100%

34
Q

Anti-TSH receptor

A

Hashimoto’s thyroiditis - 6-60%
Grave’s Disease - 70-100%

35
Q

TRH Stimulation Test

A

Inject patient with synthetic TRH after collection of baseline TSH
Collect TSH samples at 15, 30, and 60 minutes
Flat response = inability to produce TSH

36
Q

Reverse T3 Info

A

Liver converts T4 to T3, which also produces a certain % of RT3
When body is under stress, it can prevent tissues that depend on T3 from producing T3 by producing RT3
Associated with non-thyroidal illness (NTI)
Testing remains controversial

37
Q

Radioiodine Uptake Test

A

Patient given radioisotope of iodine
Gives a picture of areas of gland that are utilizing iodine

38
Q

Ultrasound Evaluation

A

Detection of small nodules
Abnormal thyroid anatomy

39
Q

Hypothyroidism

A

Deficiency in thyroid hormone activity
Can be structural or functional

40
Q

Hypothyroidism Occurence

A

As high as 15% with female preference

41
Q

Primary Hypothyroidism

A

Deficiency in thyroid hormone production

42
Q

Secondary Hypothyroidism

A

Pituitary or hypothalamic failure
- Sometimes called tertiary

43
Q

Clinical Signs and Symptoms of Hypothyroidism

A

Slowing of metabolism
Fatigue
Cold intolerance
Weight gain
Constipation
Dry Skin
Mental Slowing
Myxedema (skin on face and feet thickens)
Tongue and vocal cords may thicken
Face may become puffy

44
Q

Etiology of Hypothyroidism

A

Acquired secondary to thyroid surgery or treatment
Inflammation = Thyroiditis

45
Q

Acute Thyroiditis

A

Infection with Gram Positive Cocci
(S. pyogenes, S. pneumoniae, S. aureus)

46
Q

Subacute Thyroiditis

A

Usually viral in origin

47
Q

Chronic Thyroiditis

A

Hashimoto’s

48
Q

Hashimoto’s Thyroiditis

A

Most common cause in US
Women > Men
Genetic predisposition
Present with goiter

49
Q

Neoplasms Hypothyroidsm

A

Rare in US
Papillary carcinmona ( young patients & women)
- Forms a firm, solitary nodule

50
Q

Follicular carcinoma

A

Middle age and can metastasize

51
Q

Medullary carcinoma

A

Parafollicular cells

52
Q

Primary Congenital Hypothyroidism

A

Creatinism

53
Q

Creatinism

A

Deficiency in thyroid tissue
Inborn defects and pituitary or hyopthalamic disorders
Untreated congenital hypothyroidism can cause developmental defects

54
Q

Creatinism Symptoms

A

Respiratory distress
Skeletal malformations
Hypothermia
Physiologic jaundice beyond 3 days
Edema
Hoarse cry
Thick tongue
Mental retardation

55
Q

Creatinism Screening

A

State Health Departments as a newborn

56
Q

Thyroid Testing for Primary Hypothyroidism

A

TSH - increased
fT4 - decreased
T3 - decreased

TSH is the single most sensitive test for hypothyroidism

57
Q

Hyperthyroidism

A

Increase in circulating hormone both free and total = Thyrotoxicosis
Weight loss
Nervousness
Sweating
Heart palpitation
Heat intolerance
Muscle weakness
Goiter - Enlarged thyroid gland
Exophthalmos (eyelid retraction)

58
Q

Hyperthyroidism - Thyroid Storm

A

Emergency Situation
Associated with infection, childbirth, diabetic ketoacidosis
Tachycardia, heart failure, high fever, nausea, and vomiting
Neurologic and psychiatric disorders, coma
Untreated: 70-80% cases fatal

59
Q

Hyperthyroidism Excess Stimulators

A

Grave’s Disease - Toxic Diffuse Goiter

60
Q

Grave’s Disease Info

A

10X more frequent in women
30-50 years of age
Autoimmune
Follicles stimulated to produce excess T4
Not under normal negative feedback regulation

61
Q

Symptoms of Grave’s Disease

A

Hyperthyroidism
Goiter
Exopthalmos

62
Q

Hyperthyroidism - Other Causes

A

Toxic nodular goiter (nodules secrete hormone)
Iatrogenic and factitious causes

63
Q

Primary Hyperthyroidism Testing & Treatment

A

TSH - decreased
fT4 - increased
T3 - increased

Ablation
Medical
Radiation

64
Q

Euthyroid Syndromes

A

Refers to a condition in which thyroid function tests are abnormal in seriously ill patient
Patient does NOT have Primary or Secondary thyroid disease
Metabolism of hormones at peripheral tissues is altered or binding protein concentration is altered (usually decreased)

65
Q

Non-Thyroidal Illness (NTI) or Euthyroid Sick Patients

A

Low TBG
ICU patients
Drug therapy = Decreased TBG

66
Q

Test Summary for NTI

A

Total T4 = Decreased
- Amount of binding protein is decreased
- Artifactual result of test method
Free T4 = Decreased
TSH = Decreased
T4 = Decreased
rT3 = Increased

67
Q

Euthroid Estrogen Therapy

A

High TBG
Increased TBG from estrogen

68
Q

Euthroid Estrogen Causes

A

Birth Control Pills
Pregnancy
Estrogen Therapy

69
Q

Test Summary for Euthroid Estrogen

A

Total T4 = Increased
fT3 = Normal
fT4 = Normal

70
Q

Summary of Primary Hypothyroidism

A

Total T4 = Decreased
Free T4 = Decreased
TSH = Increased

71
Q

Summary of Secondary Hypothyroidism

A

Total T4 = Decreased
Free T4 = Decreased
TSH = Decreased

72
Q

Summary of Euthyroid Sick

A

ICU/Drugs
Dependent on degree of illness
Total T4 = Decreased
Free T4 = Decreased to Normal
TSH = Decreased to Normal

73
Q

Summary of Primary Hyperthyroidism

A

Total T4 = Increased
Free T4 = Increased
TSH = Decreased

74
Q

Summary of Secondary Hyperthyroidism

A

Total T4 = Increased
Free T4 = Increased
TSH = Increased

75
Q

Summary of Euthyroid Estrogens

A

Estrogen Therapy & Pregnancy
Total T4 = Increased
Free T4 = Normal
TSH = Normal

Chemistry (11 decks)

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