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Thyriod Function Flashcards

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
TBG
Thyroid Binding globulins
26
Albumin
Catch all carrier protein
27
Free T4
fT4 0.03%
28
Free T3
fT3 0.3%
29
Bound T4
99.97%
30
Bound T3
99.7%
31
Testing for Thyroid
Competitive binding immunoassay Stripping agent is added to remove TBG and other binding proteins
32
Thyroid Antibodies
Previously thyroid microsomal antibodies Hashimoto's Thyroiditis - 80-99% Grave's Disease - 45-80%
33
Antithyroglobulin Antibodies
Hashimoto's thyroiditis - 6-60% Grave's Disease 70-100%
34
Anti-TSH receptor
Hashimoto's thyroiditis - 6-60% Grave's Disease - 70-100%
35
TRH Stimulation Test
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
Reverse T3 Info
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
Radioiodine Uptake Test
Patient given radioisotope of iodine Gives a picture of areas of gland that are utilizing iodine
38
Ultrasound Evaluation
Detection of small nodules Abnormal thyroid anatomy
39
Hypothyroidism
Deficiency in thyroid hormone activity Can be structural or functional
40
Hypothyroidism Occurence
As high as 15% with female preference
41
Primary Hypothyroidism
Deficiency in thyroid hormone production
42
Secondary Hypothyroidism
Pituitary or hypothalamic failure - Sometimes called tertiary
43
Clinical Signs and Symptoms of Hypothyroidism
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
Etiology of Hypothyroidism
Acquired secondary to thyroid surgery or treatment Inflammation = Thyroiditis
45
Acute Thyroiditis
Infection with Gram Positive Cocci (S. pyogenes, S. pneumoniae, S. aureus)
46
Subacute Thyroiditis
Usually viral in origin
47
Chronic Thyroiditis
Hashimoto's
48
Hashimoto's Thyroiditis
Most common cause in US Women > Men Genetic predisposition Present with goiter
49
Neoplasms Hypothyroidsm
Rare in US Papillary carcinmona ( young patients & women) - Forms a firm, solitary nodule
50
Follicular carcinoma
Middle age and can metastasize
51
Medullary carcinoma
Parafollicular cells
52
Primary Congenital Hypothyroidism
Creatinism
53
Creatinism
Deficiency in thyroid tissue Inborn defects and pituitary or hyopthalamic disorders Untreated congenital hypothyroidism can cause developmental defects
54
Creatinism Symptoms
Respiratory distress Skeletal malformations Hypothermia Physiologic jaundice beyond 3 days Edema Hoarse cry Thick tongue Mental retardation
55
Creatinism Screening
State Health Departments as a newborn
56
Thyroid Testing for Primary Hypothyroidism
TSH - increased fT4 - decreased T3 - decreased *TSH is the single most sensitive test for hypothyroidism*
57
Hyperthyroidism
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
Hyperthyroidism - Thyroid Storm
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
Hyperthyroidism Excess Stimulators
Grave's Disease - Toxic Diffuse Goiter
60
Grave's Disease Info
10X more frequent in women 30-50 years of age Autoimmune Follicles stimulated to produce excess T4 Not under normal negative feedback regulation
61
Symptoms of Grave's Disease
Hyperthyroidism Goiter Exopthalmos
62
Hyperthyroidism - Other Causes
Toxic nodular goiter (nodules secrete hormone) Iatrogenic and factitious causes
63
Primary Hyperthyroidism Testing & Treatment
TSH - decreased fT4 - increased T3 - increased Ablation Medical Radiation
64
Euthyroid Syndromes
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
Non-Thyroidal Illness (NTI) or Euthyroid Sick Patients
Low TBG ICU patients Drug therapy = Decreased TBG
66
Test Summary for NTI
Total T4 = Decreased - Amount of binding protein is decreased - Artifactual result of test method Free T4 = Decreased TSH = Decreased T4 = Decreased rT3 = Increased
67
Euthroid Estrogen Therapy
High TBG Increased TBG from estrogen
68
Euthroid Estrogen Causes
Birth Control Pills Pregnancy Estrogen Therapy
69
Test Summary for Euthroid Estrogen
Total T4 = Increased fT3 = Normal fT4 = Normal
70
Summary of Primary Hypothyroidism
Total T4 = Decreased Free T4 = Decreased TSH = Increased
71
Summary of Secondary Hypothyroidism
Total T4 = Decreased Free T4 = Decreased TSH = Decreased
72
Summary of Euthyroid Sick
ICU/Drugs Dependent on degree of illness Total T4 = Decreased Free T4 = Decreased to Normal TSH = Decreased to Normal
73
Summary of Primary Hyperthyroidism
Total T4 = Increased Free T4 = Increased TSH = Decreased
74
Summary of Secondary Hyperthyroidism
Total T4 = Increased Free T4 = Increased TSH = Increased
75
Summary of Euthyroid Estrogens
Estrogen Therapy & Pregnancy Total T4 = Increased Free T4 = Normal TSH = Normal

Chemistry (11 decks)

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