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Endorepro Midterm > Thyroid Gland > Flashcards

Thyroid Gland Flashcards

1
Q

Which hormone, T3 or T4 is active?

A

T3

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2
Q

Which thyroid hormone is the main secretory product?

A

T4 (90%)

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3
Q

What is the secretory product of the thyroid gland?

A

Iodothyronines

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4
Q

How is T4 converted to T3?

A

Peripheral conversion w/ deiodinase

enzyme = 5’ - iodinase

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5
Q

Iodide =

A

I-

Inside follicular cell

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6
Q

Iodine =

A

I2

In apical lumen

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7
Q

What is a treatment for hyperthyroidsm?

A

PTU –> Inhibits peroxidase + NIS

Wolff-Chiakoff Effect –> increased levels of I- (iodide) prevents the synthesis of thyroid hormones cause you need decreased iodide for deiodinase to convert

T4 –> T3 and get them out of storage form and into blood stream

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8
Q

How is iodine stored?

A

It is stored in follicular colloids iodinated as tyrosines attached to thyrogobulin (need to use deiodinase to break them apart)

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9
Q

How can you assess the activity of the thyroid gland?

A

By radioactive iodine uptake

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10
Q

Which thyroid hormone has a longer half life?

A

T4 –> 6 days

vs. 1 day for T3

thats why T4 = most circulating hormone

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11
Q

How can we assess circulating levels of TBG?

A

With a resin uptake test

Thyroid function involves the interaction of many hormones, including triiodothyronine (T3) and thyroxine (T4). Both of these hormones exist in two forms in the blood. The more abundant forms are bound to a carrier protein called thyroxin-binding globulin (TBG), which helps transport the hormones through the body. The less abundant forms circulate unattached or “free.” Only the free forms of the thyroid hormones (free T4 and free T3) are available to affect body processes.

The T3 resin uptake is used by doctors to estimate the amount of TBG in the blood, and how much T4 and T3 in the blood is free form and available to affect the body.

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12
Q

Explain what happens to TBG, T4, and T3 in these disorders during the resin uptake test:

Hyperthyroidism

Hypothyroidism

High TBG

Low TBG

Hepatic Failure

Preganancy

A
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13
Q

What enzyme converts Iodide to Iodine?

A

Thyroid Peroxidase (via pendrin transporter)

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14
Q

What factors stimulate thyroid hormone secretion?

A

TSH

Thyroid stimulating immunogobulins

Increased TBG levels –> ex = pregnancy

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15
Q

What factors inhibit thyroid hormone secretion?

A

I- deficiency –> can’t make T3

Deiodinase deficiency

Excessive I- intake (Wolff-Chaikoff effect)

Perchlorate + thiocyanate –> inhibit Na + I- cotransport

Propylthiouracil (PTU) –> inhibits peroxidase enzyme

Decreased TBG levels –> ex = liver disease

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16
Q

What do people with hypothyrodism take?

A

Thyroxine (T4) injection, increases BMR

17
Q

Review this chart (good things to look for in stem)

A
18
Q

Are TSH levels low or high in hyperthyroidism?

A

Low

19
Q

Are TSH levels low or high in hypothyroidism?

A

High

20
Q

What is the other name for hyperthyroidism?

A

Thyrotoxicosis

21
Q

What is primary hyperthyroidism?

A

Grave’s Disease

22
Q

What causes Grave’s disease?

A

Thyroid stimulating immunogobulins (TSI’s) stimulate the TSH receptor without actually having the TSH hormone.

Soooo TSH receptor is being constantly stimulated!

But, you still have low TSH hormone cause all the high T3 + T4 hormones are stopping it from making more through negative feedback.

Remember main symptom = exophthalmos

23
Q

What causes Hashimoto’s Thyroiditis?

A

Usually thyroid gland destrction –> causing impaired thyroid hormone synthesis and decreased T3 + T4 levels

TSH = high –> causes trophic effect (Goiter)

24
Q

What is caused by untreated postnatal hypothyroidism?

A

Cretinism

25
Q

The TSH test is used for diagnosing both hyperthyroidism and hypothyroidsim.

What would the levels of TSH, T3/T4, TSI, and Radioactive Iodine Uptake test be for these diseases:

Hyperthyroidism

  1. Grave’s
  2. Thyroditis (w/ hyperthyroidism)
  3. Thyroid nodules

Hypothyroidism

  1. Hashimoto’s disease
  2. Pituitary abnormality
A

Endorepro Midterm (11 decks)

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