Endocrine Critique

Endocrine glands _____ and ______ hormones

produce and secrete

What is a Right to left shunt

hole in right ventricle to the left ventifcle

deoxygenated blood enters left side and goes systemic circut

• causes numerous issues - espeically in brain and kidneys

What is one of the biggest disadvantages of the dual-tracer parathyroid imaging compared to dual-phase?

patient has to stay on camera, and stay still for method to work well

What is the first test typically performed when evaluating thyroid function?

blood draw (blood work)

What is the function of hormones?

regulate body’s growth, metabolism, and sexual development and function

What shape is the thyroid commonly compared w/?

butterfly

What hormones does the thyroid produce?

T-3 and T-4 hormones

What is the function of the thyroid hormones?

regulates cellular activity - e.g. metabolism of cells

Describe the physiological process of the thyroid’s conversion of iodine into hormones (start from how iodine gets to the thyroid)

iodine absorved into bloodstream from digestive tract

blood transport iodine in form of iodide to thyroid gland, where it’s trapped and organified by thyroid follicular cells

iodide oxidized to form:

MIT (monoiodotyrosine

DIT (diiodotyrosine)

T-3 = 1MIT moluecule and 1 DIT molecule

T4 = 2 DIT molecules

T/F: All endocrine cells can absorb iodine

False

What endocrine cells can absorb Iodine?

thyroid cells only

T/F: the majority of all release thyroid hormones is in the form of T4

True

T/F: The majority of release thyroid hormones is in the form of T3

False

What percent of released thyroid hormone is T4 vs T3?

90% = T4

10% = T3

Metabolic activity is determined by the _____ amount of T3 and T4 hormones

free

Thyroid stimulation and it’s secretion of hormones is controlled by a _________ feedback mechanism

Negative

What hormone causes the thyroid to create and secrete T3 and T4 hormones?

TSH- thyroid stimulating hormone

Describe the negative feedback mechanism regulating the thyroid.

hypothalamus releases TRH (Thyrotropin releasing hormone) or TRF (thyrotropin releasing factor)

Pituitary gland releases TSH (thyroid stimulating hormone)

TSH causes thyroid to make and secrete T3 and T4 hormones

The hypothalamus releases ____ and ___ hormones, stimulating the pituitary gland to secrete TSH

TRH - thyrotropin releasing hormone

TRF - thyrotropin releasing factor

________ circulating hormone (T3, T4) will signal the pituitary gland to decrease the amount of TSH it is producing

Increased

________ circulating hormone (T3, T4) will cause the pituitary gland to increase the amount of TSH it is producing

Decreased,

A patients bloodwork showed elevated TSH. Does this patient have hypo or hyper-thyroidism?

hypothyroidism

A patients bloodwork showed decreased TSH. Does this patient have hypo or hyper-thyroidism?

hyperthyroidism

Hormone production problems are caused by what condition?

hyper and hypothyroidism

Mechanical issues (ex. trouble swallowing or hoarseness)  are typically caused by 

swollen gland

Nodules or lumps in the thyroid could be caused by:

cancerous lumps or leison

What can cause hypothyroidism?

Iodine deficiency or excess

inherited enzyme deficiiency

post ablation

end stage toxic

Mets

thyroiditis

pituitary or hypothalamus dysfunction

What causes primary hypothyroidism?

failure of thyroid gland to synthesize and release thyroid hormones

What causes secondary hypothyroidism?

TSH is deficient

can be either congenital or from tumor in pituitary

In patients w/ hypothyroidism, ___ will be elevated, and ___ will be low

TSH will be elevated

T4 willl be low

In patients w/ hyperthyroidism, ____ will be low, and _____ will be elevated

TSH will be low

T4 will be elevated

What are some causes of hyperthyroidism?

Grave’s disease

Solitary nodule

Multinodular goiter (MNG)

Thyroiditis

What are some symptoms of hyperthyroidism?

(unofficially: think about Gary)

Elevated metabolic rate

Excessive perspiration

Rapid, Irregular heartbeat

Nervousness

Weight loss

Exophthalmos: protrusion of the eyeballs caused by edematous tissue behind the eyes

What are some symptoms of hypothyroidism?

Low metabolic rate

Always cold

Constipation

Dry skin

Weight gain

Puffy face

Hair loss

What is Myxedema?

Swelling of the body or face that often accompanies hypothyroidism.

What does thyroid storm mean?

Sudden release of large amounts of thyroid hoormones

What is Exophthalmos?

bulging of eyes that often accompanies hyperthyroidism

What does Goiter mean?

swelling of the thyroid gland

What is Cretinism?

infantile hypothyroidism - shows stunted growth, thickened facial features, abnormal bone development and delay in mental development

How is hyperthyroidism treated?

Surgical resection

radioactive iodine treatment

anti-thyroid medications

beta blockers (only treats symptoms)

How is hypothyroidism treated?

hormone replacement medications

What signs/symptoms of Benign thyroid nodules?

family history of Hashimotos thyroiditis or benign thyroid nodule or goiter

• symptoms of hyper or hypothyroidism

• pain or tenderness associated w/ a nodule

• Soft, smooth, mobile nodule

• simple cyst on ultrasound

What is the palatable difference between a benign thyroid nodule and a malignant nodule?

Benign - soft, smooth, mobile nodule

Malignant - firm, irregular, and fixed nodule

What are some signs and symptoms of malignant thyroid nodules?

common in ages < 20 or age >70

• new onset of swallowing difficulties or hoarseness

• history of external neck irradiation during childhood

• firm, irregular and fixed nodule

• presence of cervical lymphadenopathy (swollen hard lymph nodes in the neck)

• previous history of thyroid cancer

• nodule that is "cold" on scan

• solid or complex on ultrasound

What are the indications for a thyroid WB scan?

pre-ablation

post-treatment

routine follow up

What is the ½ life, energy and emission of I-131?

8.1 days

364keV

Gamma and Beta

What is the ½ life, energy and emission of I-123?

13hrs

159keV

Gamma

What is the ½ life, energy and emission of Tc-99m?

6hrs

140keV

gamma

What is the energy of I-131?

364keV

What is the energy of I-123?

159keV

What is the ½ life of I-131?

8.1 days

What is the ½ life of I-123?

13hrs

What is the mechanism of uptake of I-131 or I-123?

Organified by the thyroid - bound to thyroglobulin

What is the mechanism of uptake of Tc-99m pertechnetate?

active transport - trapped in follicle

What are the contraindications for a thyroid study?

Meds that have not been stopped

What pt. history should be acquired prior to a thyroid scan?

Family history of cancer/thyroid disease

Taking any thyroid medication or anything that contains iodine

Neck swelling or lumps

Weight changes / comfort or discomfort with base temperature

Recent Xrays, taking vitamins

Lab work

What restrictions/patient prep should be followed prior to a thyroid NM study?

low iodine diet

anti-thyroid medications

hormone replacements

What is the dose of I-123 for a thyroid uptake scan?

200-300 µCi I-123

What is the dose of I-131 for a thyroid uptake?

5-10µCi I-131

When can you obtain counts for a thyroid uptake scan? When are counts most commonly obtained?

@ 2, 4, 6, 24, or 48 hrs

most commonly obtained @ 24 hrs

How do you calculate the % of radioactive iodine uptake?

% Uptake =

[(net neck counts - net thigh counts)x 100]

(net standard counts - background counts) (decay factor)

Calculate the uptake of this patient @ 4hrs:

4 hour uptake: 4 hour decay factor= 0.810

 Capsule   734,915 cpm

 Bkgd   103 cpm

 Thyroid  29,760 cpm

 Thigh  683 cpm

                       29,760 cpm – 683cpm

%uptake= ----------------------------------------------- x 100 = 4.8%

                       (734,915 cpm – 103cpm)(0.810)

What is a normal radioactive iodine uptake values @ 4-6 hrs?

5-20%

What is a normal radioactive iodine uptake values @ 24 hrs?

7-35%

 < __ uptake of radioactive iodine @ 24hrs would indicate Hypothyroidism

<7%

> __ uptake of radioactive iodine @ 24hrs would indicate hyperthyroidism

>35%

What uptake value range would indicate hypothyroidism?

< 7%

What uptake value range would indicate hyperthyroidism?

> 35%

What tracers can we use for a thyroid scan?

I-123 

Tc-99m pertechnetate

What is the Tc-99m pertechnetate dose for a thyroid scan?

2-10 mCi Tc-99m pertechnetate

Imaging for a thyroid scan using Tc-99m would begin ____ post inj

15-30 min

When would imaging for a thyroid scan using Tc-99m Pertechnetate begin?

15-30min post inj

How is Tc-99m Pertechnetate given for a thyroid scan?

Via IV

What is the dose for I-123 for a thyroid scan? How is it given?

200-500 µCi

Via IV

When are images taken for a thyroid scan using I-123?

4hrs

18-24hrs delay

Images using I-123 for a thyroid scan can be acquired @ ___ and ___ hrs post administration

4hrs

18-24hr delay

What views are acquired for a thyroid scan using I-123 or Tc-99m Pertechnetate?

Anterior

Anterior with marker

RAO

LAO

What type of collimator is used for a thyroid scan using I-123 or Tc-99m pertechnetate?

pinhole

What are the imaging acquisition time parameters for a thyroid scan using Tc-99m?

100,000-200,000 count image or 5-min

What are the imaging acquisition time parameters for a thyroid scan using I-123?

50,000-100,000 counts or 10min

What does normal uptake on a thyroid scan look like?

• Euthyroid / homogenous uptake

• Lt typically smaller than rt plus pyramidal lobe

• Location – inferior thyroid cartilage and superior to supra sternal notch

• Uptake = or > salivary gland

What is the energy peak of Co-57?

122keV

Uptake was 10.15%. Is this scan normal or abnormal

normal

How would Plummers – autonomous multinodular goiter, appear on a Thyroid scan?

hot or cold solitary or multiple

If a patient w/ the clinical symptoms of hyperthyroidism but no visualization of the thyroid on the scan, what could this be a sign of?

thyroiditis

How would thyroiditis present on a thyroid scan? 

non visualization of the thyroid, but clinical symptoms of hyperthyroidism

How would graves disease present on a thyroid scan?

enlarged, high uptake

How would Hashimotos thyroiditis present on a thyroid scan?

enlarged, mottled

How would thyroid cancer present on a thyroid scan?

solitary nodules - typically cold, sometimes hot

What types of artifacts may appear on a thyroid scan?

Iodine contaminants I-123

• Tc99mO4- less accurate, lower uptake high background

Metal on neck

Improper collimator for isotope

Markers being placed incorrectly

Patient movement

What types of variations can we use when performing a thyroid scan? What are the reasons for these?

Perchlorate wash-out - test for problems w/ organifcation

• i.e. Hashimotos or congenital enzyme deficiencies

TSH and TRH stimulation tests

T3 – triodothyronine (cytomel) suppression test to diagnose hyperthyroidism

The 24hr calculated uptake was 73%. What is your impression of this scan?

hyperthyroidism - Graves disease

What is your impression of this scan?

cold nodule

Pt. is a 61 year-old female with suppressed (low) TSH, and a diffusely enlarged thyroid. What is your impression of this scan?

Toxic Multinodular Goiter

Why should you obtain lateral views for a thyroid scan for pediatric patients?

bc thyroid originates sublingual-ly

What are the 2 types of thyroid cancer?

Papillary

Follicular

What is the most common type of thyroid cancer? Papillary or Follicular

papillary

Why do we use high doses of I-131 to treat cancer, compared to a relatively low dose for treating hyperthyroidism?

Bc we are trying to treat relatively small amounts of thyroid tissue

when treating hyperthyroidism, relatively larger target

want to minimize target to non-target radiation exposure 

For a thyroid uptake scan:

• does the patient typically have a thyroid

• what radiopharms can we use

• and what images are we acquiring

yes - although can be part of i-131 pretreatment scan, in which case there is no thyroid

I-123 or I-131

n/a - acquiring counts not images

For a thyroid scan:

• does the patient typically have a thyroid

• what radiopharms can we use

• and what images are we acquiring

yes - although can be part of i-131 pretreatment scan, in which case there is no thyroid

I-123 or Tc-99m O4

• Ant

• Ant w/ marker

• obliquee