Thyroid NM Flashcards
Thyroid location
Level of II and III tracheal rings
4-5 cm by 1.5-2 cm
Thyroid weight
6-20 g
Pyramidal lobe
At surgery 80%
Remnant of thyroglossal duct
Can hypertrophy after thyroid resection
C cells = parafollicular cells
From neural crest
1% of cell population
Secrete Calcitonin in response to Calcium elevation
Express somatostatin receptors, Calcitonin generated peptid, gastrin releasing peptide
Medullary thyroid carcinoma
Independent of TSH
Inable to concentrate iodine
Nontoxic multinodular goiter
Increased thyroid hormone production
Only nodules >1 cm should be evaluated or <1 cm if malignant nature
Non palpable nodules ==same risk of malignancy as US confirmed palpable same size
Areas of iodine def - - goiter
4-17% fulfill criteria of malignant change, but majority is not malignant
Therapy with I131 to avoid surgery
100 microCi per g of thyroid tissue
Toxic Adenoma = Plummer Disease
TSH receptor mutation - - receptor is always activated - - rest of gland rest
Treatment with I131 in the phase of דיכוי - - kill adenomatous cells
Fixed max activity 16 mCi
Risk - genetic, female
Graves disease
AB to TSH receptor
60-80% of thyrotoxicosis
High iodine intake
Women, 20-50
Graves disease US
Diffusely enlarged
Increased vascularity on Doppler - - thyroid inferno
vs Hashimoto (normal blood flow)
Graves disease treatment
Antithyroid drugs = PTU, methimazole - - bone marrow tox, liver tox, relapse
Radioiodine therapy
Thyroidectomy when large goiter - - bleeding, laryngeal edema, hypopara, damage of recurrent laryngeal nerve
Graves disease Radionuclide treatment
I131 - - progressive destruction by beta, highly effective, cure rate 100%
Radiation thyroiditis 1-2 weeks after - - pain in anterior cervical region, thyrotoxic crisis (cytolysis)
Persistent hyperthyroidism - - second dose 8-12 months later
Fixed dose 5, 10, 15 mCi
Can conceive 6 months after
Use steroids if Ophtalmopathy
Hashimoto thyroiditis
Most common autoimmune disease, endocrine disorder, cause of hypothyroidism
Chronic inflammation
Enlarged, lymphocytic infiltration of thyroid, hypothyroidism
Primary ass with autoimmune disease
Hashimoto thyroiditis US
Hypoecho
Ground glass
Pseudonodules = bag of marbles
Tiny cystic lesions = Swiss cheese - - 2-3 mm
Fibrosis - - septa
Other forms of thyroiditis
Infectious (not viral)
De Quervain = subacute - - viral - - release of preformed thyroid hormone - - hypoecho to one lobe or a portion of lobe - - painful, palpable
Autoimmune
Riedels = chronic sclerosing thyroiditis - - overgrowth of connective tissue
Postpartum
Amiodarone
Risk for malignancy US
Microcalcification
Irregular or microlobulated margins
Hypoecho
Taller-than-wide
Hypervascular
Combi of at least 2
Tc pert
Beta and gamma, 140 keV, 6h
Iodomimetic
Transport through Na/I symporter, no organification
Max accumulation 15-20 min after IV, plateau 30 min
Image not later than after 30 min
1-10 mCi
5 min or 100000-200000 counts
High dose, high count, no preparation, lower radiation exposure
Nursing in 12-24h
I123
Pure gamma, 159 keV, 13h
Higher specificity and persistence of accumulation due to organification
Higher resolution, better visualisation of retrosternal, children, in case of low thyroid uptake
3-4h after PO 100-400 microCi
10 min or 50000-100000 counts
Breast feeding in 48 h
I131
Beta and gamma 364 keV 8 days
Limited to uptake test, monitoring of DTC treatment, ectopic thyroid (retrosternal, lingual, struma ovarii), dosimetric pretreatment evaluation
High gamma–no sternal attenuation
24h after PO
10 min or >50000 counts
Pitfalls
Medication, CT contrast - - no uptake
Acute/subacute thyroiditis
Therapy with TSH suppressive doses of HRT
Hyperthyroidism (too much hormones)
Local contamination
Esophageal activity - - drink water
Nodules
Hot = hyperfunctioning - - almost never malignant
Cold = hypofunctioning - - 3-15% malignant
Indeterminate - - 3-15% malignant
Predictive value is low, esp if nodule <1 cm
RAIU
I131 PO 30-100 microCi
Measure at 4h and 24h
24h <20% - - no therapy
Radionuclide Therapy
I131, beta, 2.4 mm range in tissue
Cellular necrosis, inflammation, follicles destruction, fibrosis
Goal - to achieve hypothyroidism and reduce volume
Radionuclide therapy of benign
preparation
2 weeks low-iodine diet
4 weeks CeCT
3 months Amiodarone (definitive treatment for Amiodarone-induced thyrotoxicosis
3 weeks Lugol, topical iodine, Li (can block release from thyroid)
Radionuclide therapy and
Elderly, heart disease, systemic illness
Pretreatment with thionamides (PTU, MTMZL) to avoid radiation induced thyroiditis
Stop 3-5 days before, resume 2-3 days after to prevent thyroid storm
Beta blockers - no need to stop
Radionuclide therapy and pregnancy
Abs Contra
Fetal thyroid concentrates iodine by week 10-13
Stop breastfeeding and no resume
Radionuclide therapy and iodine sensitivity
Safe
Surgery benign
Tracheal narrowing <1 cm - - steroids
<5-6 mm - - surgery
80 g gland - - surgery
Induced hypothyroidism
2-3 months after radioiodide therapy
Levothyroxine as soon as TSH elevation is detected
Radioiodide therapy side effects
Inflammation with edema
Transitory hyperthyroidism - - steroids and beta blockers to prevent
Rare - - autoimmune thyroid disease 2-6 months after
Ophtalmopathy - - stop smoking, take steroids, start HRT after treatment
Efficacy of radioiodine treatment
Volume reduction to 30-40% within 1 year
Further reduction to 50-60% next year
Within 2-3 years hypothyroidism
Malignant thyroid disease
Thyroid nodule - - 4-5% of all thyroid nodules
Women
Sporadic/familial
Differentiated TC: papillary and follicular
Anaplastic TC = Stage IV
Medullary TC
Thyroid cancer M
Lung (PTC and young)
Bone (FTC and old)
Skin
Brain
Associated disease with Thyroid cancer
Gardner syndrome
Cowden syndrom - - FTC
RET oncogene
Hashimoto - - thyroid lymphoma
PET indication for thyroid cancer
DTC
Post Thyroidectomy
Eleveted Thyroglobulin
Negative I131 WBS
Tumor become iodine insensitive - - flip-flop - - FDG avid
ATC
Stage IV
IVB unresectable
Rapid grow - - big firm nodule, recently developed, 3-15 cm
Dysphonia
Dysphagia, dyspnea
30-40% regional LN and vocal cord paralysis
Surgery, chemo, EBRT
Very poor prognosis
Death from airway obstruction
Dedifferentiation of DTC
44% of ATC had previous or concurrent DTC
ATC mutations
BRAF V600E
RAS + BRAF - - resistance to vemurafenib
MTC
C-cells
Sporadic 75%
MEN2 - - 100% MTC, 50% pheo, 20-30% PHP
Hereditary - - RET mutation
Only 1% low diff - - do not produce Calcitonin - - marker
Well-diff
Elevated Calcitonin
Renal failure
Autoimmune disease
Hyperpara
FTC
Net of Pancreas
Prostate ca
Lung ca
Calcitonin in stimulation test with calcium, pentagastrin
Do not increase
MTC treatment
Surgery
I131-MIBG
Y90- and Lu177 DOTA - TOC/NOC/TATE
Advanced/recurrent/metastatic - - TKI
ATA guideline FNA
> 1 cm with high suspicion
1 cm with intermediate suspicion
1.5 cm with low suspicion
2 cm with very low suspicion (spongiform)
Cytology
Thy1 - nondiagnostic aspirate
Thy2 - benign
Thy3 - cytology is not diagnostic
Thy4 - suspicious for malignant
Thy5 - malignant
DTC NM
Espression of NIS gene reduced - - cold nodule - - can be benign nonfunctioning adenoma
Thyroid scan low specificity
FDG - - 4% increased focal uptake in thyroid - - incidentaloma - - 20% malignant
ATC NM
High levels of GLUT1 and GLUT3– FDG the best
US, CT, MRI for defining local extent
MTC NM
Neuroendocrine features
Express receptors for somatostatin - - MIBG image and therapy, FDOPA, radiolabeled somatostatin analogs therapy
FDG is suboptimal
Normal Calcitonin - - excellent response - - 10 year survival 100%
Useless imaging if Calcitonin <150 pg/mL
Calcitonin >150 pg/mL
Neck US
LN recurrence most common
Calcitonin >500 pg/mL
CT, MRI, PET
Thyroid cancer T
Thyroid cancer N
VI, VII
II-V
retropharyngeal
Thyroid cancer M0
<55 years - - Stage I
Thyroid cancer M1
<55 years - - Stage II
Thyroid cancer surgery
FTC - - solitary nodule
PTC - multifocal growth - - total Thyroidectomy - - vocal cords palsy, permanent hypopara
PTC in single small nodule - - lobectomy + neck US
Central LN dissection
Adjuvant ablation of postsurgical remnant
DTC - - to eliminate any residual, macroscopically normal thyroid left
TSH stimulation > 30 microIU/mL: stop L-thyroxine for 4-6 weeks or rhTSH 0.9 mg IM 2 days
I131 ablation 30-100 mCi
WBS 4-7 days after
No benefit from ablation
Tumor <1.5 cm
LN negative
Unifocal microcarcinoma T1a
Ablation preparation
2 weeks low-iodine diet
Stop L thyroxine for 4-6 weeks to TSH > 30 microIU/mL or rhTSH
Urine iodine content
Iodine / creatinine ratio <250 microg/g
NPO from midnight
LN suspicious
FNA, Tg
<1 cm - - I131 therapy
Bigger - - surgery, radioiodine therapy
Recurrent DTC
Poorly diff - - do not concentrate iod
FDG
TKI sorafenib and Lenvatinib
Thyroid stunning
Prior diagnostic I131 - - non ablative up to 10 Gy - - reduced NIS expression in response to irradiation induced DNA damage - - 50% reduced ability to concentrate and store radioiodide - - reduced uptake
If I131 as preablation assessment - - no more than 2 mCi and ablation within 48-72 h
I123 used as preablation assessment
Auger electrons
No stunning effect
15% of DTC dedifferentiate
After several courses of I131
Retinoic acid
Selumetinib
Reinduce iodine uptake ability
DTC +MTS, non iodine avid, rapidly grow
Only Doxorubicin
Radioiodine ablation
Relative Contra
Bone marrow depression
Impaired pulmonary function - - significant accumulation
Intracranial DTC lesion - - oedema and compression
Functional deficit of salivary gland
Radioiodine ablation
Side effects
Hypothyroidism 2-3 weeks after reintroduction of L-thyroxine
Nausea, gastric pain - - PPI
Sialoadenitis - - fluids and lemon juice
Loss or change of taste
Steroid to prevent radiation induced inflammation
Transient impairment of male gonadal function
Second malignancy or leukemia
After repeat ablation + EBRT
>500 mCi
Exposure to I131 affects outcome of pregnancy and offspring
No evidence
Diffuse lung MTS
Radiation fibrosis if 150 mCi at short intervals <6 months
<80 mCi after 48h
Levothyroxine treatment
PTC, FTC Post-op
To correct post op hypothyroidism
To suppress secretion of TSH
Young - - higher dose
T3 and T4 should be normal
No adverse effects on bone maturation, final height, pubertal development
Not to take the morning before blood test - - increase T4 by 25%
Aim - - TSH 0.1-0.5 microIU/mL
Iodine daily requirement
150 microg
Bread, milk, seafood
24h uptake <10-15%
Stimulation with recombinant human TSH
0.3 mg for MNG
0.9 mg for DTC
Measure radioiodine dose for MNG
Thyroid mass * 3.7 MBq = initial activity
Uptake 30% - - thyroid mass *3.7 : 0.3
Most common of all thyroid disease
MNG
Most common cause of hyperthyroidism
Graves
Toxic Adenoma
Graves disease risk
Infections
Iodine intake
Smoking
Psychic stress
Graves disease lab
Elevated bilirubin, liver enzymes, ferritin
Microcytic anemia. Thrombocytopenia
Thyroid scintigraphy
Indication
All cases of thyroid nodule
MNG if TSH is low
Ectopic thyroid
Retrosternal goiter
C cells vs follicular cells
Junction of Upper 1/3 and lower 2/3, along central axis
Functional independence from TSH
Inability to concentrate and retain iodide
Production and secretion of Calcitonin
Ablation
Indication
DTC moderate - high risk
No role - in ATC and poorly diff TC - - do not concentrate iodine
Benefits from adjuvant ablation
Decrease recurrence
Early detection
Sensitive I131 WBS
Any subsequent I131 therapy will be more effective
Ablation successful
90% if uptake in residue <2% - - residual mass <2g
2/3 if uptake in residue >2% - - residual mass >2g
T3 three times per day
Tachycardia
DTC follow up after primary treatment 6-12 m
Serum Tg - - 20-25% anti Tg autoAB interfere - - not reliable
Undetectable under L-thyroxine suppressive therapy - - confirm with TSH stimulation test - - can be avoided if basal Tg <0.1 ng/mL, but reserved for gray zone 0.1-1 ng/mL
Cutoff Tg 2 ng/mL (FDA 2.5 ng/mL)
I131 WBS
Neck US
Bulkier recurrence limited to LN
Surgery
No uptake on post treatment WBS
Stop treatment with I131
Uptake %
Graves 50-80%
MNG 20-30%
Normal 4h 4-15%
Normal 24h 10-30%
Tc pert high radiation dose to thyroid
Beta
High gamma
Long T1/2
Contaminants I124 and I125 increase radiation dose
Cold nodule
10-30% risk of malignancy
Nodule hot on Tc pert, but cold on I123
2-3%
Uptake dd thyroiditis vs Graves
Thyroiditis - - abnormally low
Graves - - abnormally high
Thyroid whole body scan biodistribution
Stomach, urinary clearance
Remnant thyroid or MTS
1 weeks after administration of 100 mCi I131
Residual tissue in thyroid bed
Local MTS under ablation
Physiological liver uptake
No uptake in stomach and small bowel - - >48h
FDG thyroid cancer
ATC
MTC
Hurtle cell
FDG diffuse bilateral uptake
Thyroiditis
Graves
Hypothyroidism
