Endocrine GW Flashcards

1
Q

Thyroid hormones

A

T3 triiodothyronine

T4 tetraiodothyronine

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2
Q

What cells trap iodide in thyroid

A

Thyroid follicular cells trap iodide through the iodide pump

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3
Q

Iodide is oxidized to form 1 of 2 molecules

A

MIT or DIT

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4
Q

One MIT and one DIT molecule =

A

T3

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5
Q

One DIT and one DIT molecule =

A

T4

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6
Q

What does the anterior pituitary gland produce and secrete

A

TSH - thyroid stimulating hormone

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7
Q

Hypothalamus produces and secretes what hormone

A

TRF - thyrotropin releasing factor

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8
Q

Which RP can be used for but is not recommended for routine imaging

A

I131

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9
Q

Indications for thyroid imaging

A

Relate gland structure to function
Evaluate size and nodules/masses
Identify ectopic tissue

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10
Q

Thyroid RPs and doses

A

pertechnetate 2-10 mCi (imaging)

I123 0.1-0.2 (uptake)
- 0.2-0.6 (imaging)

I131 0.004-0.01 (uptake)
- 0.05 - 0.2 (imaging)

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11
Q

Administration to imaging time for each RP for thyroid

A

Pertechnetate 15-30 minutes

I123 3-4 or 16-24 hours

I131 6-24 hours

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12
Q

How long may a low iodine diet be recommended prior

A

3-10 days prior

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13
Q

How to magnify views with pinhole collimator

A

Bring collimator closer to neck

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14
Q

Most interfering drugs and procedures must be withheld

A

2-4 weeks

Thyroxine (thyroid med) 4-6 weeks

Antithyroid meds 2-8 days

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15
Q

Which lobe of thyroid is larger

A

Right

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16
Q

Nonfunctioning “cold” nodules means

A

Cancer
Cyst
Hematoma
Inflammatory conditions
Benign adenoma

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17
Q

Hot nodules mean

A

Typically benign

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18
Q

Thyroid uptake at 2-6 hours reflects what function

A

Iodide trapping and organification

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19
Q

Iodide uptake is useful for

A

Hyperthyroidism who need i131 therapy
Organification defects
Thyroiditis

20
Q

Thyroid uptake and imaging prep

A

Fast from midnight the night before and for 2 hours after taking pill

21
Q

What distance is the uptake probe

A

25-30 cm

22
Q

Normal uptake values

A

4 hours: 6-18%

24 hours: 10-35%

23
Q

Factors that can increase uptake

A

Iodine deficiency
Pregnancy
Lithium
Rebound after stoping thyroid meds

24
Q

Factors that can cause decreased uptake

A

Renal failure, severe congestive heart failure
Excess iodine including recent contrast
Meds containing T4 and antithyroid meds

25
Q

Whole body thyroid imaging after thyroidectomy to identify residual tissue or areas of mets RP and dose

A

I131 1-10 mCi (controversial)

123 1-2 mCi (is being considered)

26
Q

Administration to imaging time for WB thyroid imaging

A

24 hours

48 optimal?

27
Q

TSH level must be _____ before WB thyroid residual post thyroidectomy imaging

A

Greater than 30-50 mU/L

28
Q

Parathyroid imaging is useful for

A

Hyperparathyroidism

  • excess PTH
29
Q

Excess PTH does what

A

Stimulates removal of calcium from bones and causes hypercalcemia in the blood

30
Q

Parathyroid imaging pt prep

A

None

31
Q

Parathyroid dual phase RP, dose, and technique

A

99mTc Sestamibi 5-25 mCi
-Localizes in both thyroid and parathyroid but washes out of thyroid

Early imaging (10 mins)
And delayed imaging (1.5-2.5 hours)

32
Q

Parathyroid dual tracer RPs and where they localize

A

99m Tc pertechnetator OR i123
-localize in thyroid
AND
99mTc sestamibi OR Tl201
- localizes in both thyroid and abnormal parathyroid

33
Q

Which RP is subtracted from which in dual tracer parathyroid imaging

A

The ones that localize in thyroid or subtracted from the ones that localize in abnormal parathyroid

34
Q

What pathology is often coincided with hyperparathyroidism

A

Thyroid disease - can cause false positive and non uniform uptake

35
Q

Which parathyroid technique has more advantages

A

Dual phase

36
Q

Which RP should go first in dual tracer parathyroid

A

Either one but the advantage to tech going first is that the pt doesn’t have to remain in one position as long as

37
Q

Disadvantage of tech/Tl201 dual tracer parathyroid imaging

A

Downscatter

38
Q

Adrenal gland cortex produces

A

Steroid hormones
-cholesterol is a building block

39
Q

Adrenal medulla produces what hormone

A

Catecholamines

40
Q

RP and dose used to image adrenal medulla

A

I123 mIBG 10 mCi
I131 mIBG 0.5 mCi

41
Q

RP used to image adrenal cortex

A

I131 radiolabeled cholesterol

42
Q

Where is free iodine secreted

A

Urine

43
Q

Adrenal imaging acquisition

A

I131 - Imaged at 1, 3, and 7 days

I123 - 24-48 hours

*Image from vertex to pelvis

44
Q

Normal i123 or i131 mIBG uptake

A

Liver, spleen, heart

Maybe salivary glands and bladder from free iodine

45
Q

Pt prep for adrenal imaging

A

Lugols solution 1 day prior and 6-7 days after administration

46
Q

Common antithyroid drugs

A

Propylthiouracil, methimazole (tapazole), carbimazole

47
Q

Common thyroid meds

A

Synthroid, cytomel, levothyroxine