Thyroid Function Flashcards

1
Q

What are the two types of cells in the thyroid gland?

A

Follicular and parafollicular

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2
Q

What thyroid hormones do follicular cells make and secrete?

A

T4 (L-thyroxine)

T3 (L-triiodothyronine)

rT3 (reverse T3 (biologically inactive))

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3
Q

Where are hormones stored in follicular cells?

A

Lumina of the follicle

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4
Q

What hormones do parafollicular cells secrete?

A

Calcitonin (involved in calcium regulation)

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5
Q

List the functions that thyroid hormones are involved in

A

Rate of O2 consumption

Growth

Sexual maturity

Protein and carbohydrate metabolism

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6
Q

TRH

A

Released by hypothalamus and stimulates anterior pituitary to secrete TSH

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7
Q

TSH

A

Regulates synthesis and release of the thyroid hormones

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8
Q

What regulates the secretion of TSH?

A

TRH

somatostatin: inhibitory factor

FT3 and FT4: stimulate hypothalamus to secrete somatostatin. Exert neg feedback to anterior pituitary to inhibit TSH secretion

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9
Q

H-P-T axis

A

The negative feedback loop of TRH and TSH

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10
Q

Thyroid hormones circulate the blood bound to what?

A

Thyroxine-binding globulin (TBG)

Thyroxine-binding prealbumin

Thyroxine-binding albumin

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11
Q

T/F:

Biologically inactive = physiologically active

A

TRUE

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12
Q

What is the function of TBG?

A

Principle carrier protein

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13
Q

FT3 and FT4 are physiologically ___

A

Active

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14
Q

T/F:

T3 is 4-5 times more metabolically potent than T4

A

TRUE

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15
Q

What is the most useful test for assessing thyroid function

A

TSH

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16
Q

Characteristics of hypothyroidism

A

TSH is minimally increased

FT4 stays within normal range

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17
Q

Characteristics of subclinical hyperthyroidism

A

TSH is low

FT4 is normal

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18
Q

T/F:

Up to 90% of thyroid hormone are protein bound

A

FALSE

MORE than 99.9% of thyroid protein are protein bound

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19
Q

T/F:

alteration in thyroid hormone binding proteins frequently lead to total T4 outside of normal range without representing true clinical thyroid dysfunction

A

TRUE

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20
Q

Thyroid produces approximately ___% of T3

A

20%

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21
Q

T3 contains 3 atoms of ___

A

Iodine

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22
Q

T/F:

FT4 makes up a large fraction of total thyroxine

A

FALSE

Small fraction because most are bound to thyroid carrier proteins

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23
Q

FT4 is the ___ ___ fraction of T4

A

Biologically active! It can enter the tissues.

24
Q

FT3 is elevated in ___

A

Hyperthyroidism

25
Q

What can cause the leakage of Tg into the bloodstream

A

Destruction through autoimmune hypothyroidism

OR

Inflammation of the thyroid

26
Q

In what condition do we see anti-Tg autoantibodies in 12%-30% of patients?

A

Grave’s disease

27
Q

What antibody does this describe:

Active, complement, and play an important role in the pathogenesis of hypothyroidism

CHECK THIS NOTECARD BECAUSE THE SLIDE NEEDS TO BE FACT CHECKED

A

Thyroperoxidase antibody (TPO)

28
Q

The production of this stimulating antibody can cause all forms of autoimmune thyrotoxicosis

A

Thyrotropin Receptor Antibody (TRAb)

29
Q

Grave’s disease is the most common cause of ___

A

Hyperthyroidism

30
Q

Hashimoto’s thyroiditis causes ___

A

Hypothyroidism

31
Q

In Grave’s disease, ab are produced that are directed at ___ ____

A

TSH Receptor (TSHR)

32
Q

In what condition can we observe the growth of the thyroid gland and goiter?

A

Grave’s Disease

33
Q

In what condition to antibodies lead to decreased thyroid hormone production as the thyroid gland is being destroyed

A

Hashimoto’s thyroiditis

34
Q

What does low Radioactive iodine uptake (RAIU) suggest?

A

Gland is metabolically inactive

35
Q

What does high Radioactive iodine uptake (RAIU) suggest?

A

Gland is metabolically active and producing significant amounts of thyroid hormone

36
Q

Why would we use a thyroid ultrasound?

A

To detect non-palpable nodules using high frequency sound waves

37
Q

What is a fine needle aspiration (FNA) biopsy?

A

First step and most accurate tool in the evaluation of thyroid nodules in the absence of hyperthyroidism

38
Q

How is hypothyroidism defined?

A

Low FT4

Normal-High TSH

39
Q

List primary conditions of hypothyroidism

A

Hashimoto’s

Treatment for toxic goiter

Excessive Iodine Intake

Subacute thyroiditis

40
Q

What is a secondary condition of hypothyroidism

A

Hypopituitarism

41
Q

What is a condition of tertiary hypothyroidism

A

Hypothalamic dysfunction

42
Q

What is thyrotoxicosis?

A

Many findings that result when peripheral tissues are presented with, and respond to, and excess of thyroid hormone

43
Q

What are potential causes of thyrotoxicosis?

A

Excessive thyroid hormone ingestion

Leakage of stored thyroid hormone from thyroid follicles

Excessive thyroid gland production of thyroid hormone

44
Q

What are symptoms of Grave’s disease

A

Thyrotoxicosis, goiter, opthalamopathy, dermopathy (orange peel skin(

45
Q

How do you treat thyroid disease associated with Grave’s?

A

1) Medication
2) Radioactive Iodine
3) Surgery

46
Q

What causes a toxic adenoma?

A

Autonomously functioning thyroid tissue (no TSH needed)

47
Q

What are treatment options for toxic adenoma / multinodular goiter

A

1) Surgery
2) Radioactive iodine
3) Thyroperoxidase inhibitor medications

48
Q

T/F:

Radioactive iodine often kills both the hyperactive nodule as well as functioning thyroid tissue

A

FALSE

Tends to only kill hyperactive nodules, leaving behind functioning thyroid tissue

49
Q

Amiodarone-Induced Thyroid Disease

A

A drug used to treat cardiac arrhythmias that that interfere with normal thyroid function

50
Q

What are characteristics of amiodarone?

A

A drug that is fat soluble with a long half life of 50 days

51
Q

Subacute thyroiditis

A

Conditions associated with inflammation of the thyroid gland, leakage of stored thyroid hormone, followed by repair of the gland

52
Q

What is the most common form of subacute thyroiditis?

A

Postpartum thyroiditis (5-9% of women in postpartum)

53
Q

TSH, T3, and FT4 in nonthyroidal illness and thyroid nodules

A

LOW TSH

LOW T3

LOW FT4

54
Q

T/F:

Thyroid nodules are common and are often not thyroid cancer

A

TRUE

55
Q

What is nonthyroidal illness or euthyroid sick syndrome?

A

Abnormalities in thyroid function tests without thyroid dysfunction

(Often in hospitalized or critically ill patients)