Parathyroid NM Flashcards
Parathyroid
2 pairs of gland
642 mm
30-50g
2-5% more glands
Cells
Chief
Oxyphilic
Transitional Oxyphilic
PTH
Stimulate bone resorption
Decrease tubular resorption of Phosphate
Stimulate synthesis of active form of Vit D - - stimulate calcium absorption in GIT
Primary Hyperthyroidism
Elevated PTH, Ca, fracture risk
Reduced serum phosphate
Cakcium/phosphate high in urine
PTA - - 85% single adenoma
Hyperplasia or multiple adenoma 15%
Carcinoma 0.5-1%
PHP familial
MEN1 and MEN2
PHP-jaw tumor sy
Familial hypocalciuric Hypercalcemia
Familial isolated PHP
Ectopic PTA
15-20%
Ant sup mediastinum
Post sup mediastinum along esophagus
Lower third lobe 2-3%
Middle mediastinum - very rare
Secondary hyperparathyroidism
Long hypocalcemia
Chronic renal failure - - 90% of patients with dialysis get PHP
Tertiary hyperparathyroidism
Persisting hyperparathyroidism after treatment of secondary
After kidney transplantation
Hyperplasia of all 4 glands, 20% single or double
Surgery outcome
5-10% - - persistent/recurrent HPT
Recurrent - - 6 months of normocalcemia - - regrowth
Persistent - - Immediate failure of surgery to restore normal PTH and Calcium
Radionuclides
Tc-Sestamibi - - both thyroid and parathyroid - - washout
Tc-tetrofosmin
Tl-Chloride - - both
Se-Methionine - - both
False positive
Thyroid carcinoma
Sarcoidosis
Lymphoma
MIBI uptake
Lipophilic - - fast transmembrane diffusion - - mitochondria
Both in thyroid and parathyroid within minutes
Release much faster from thyroid - - washout
80-90% sensitive for parathyroid malignancy, but no dd
After parathyroid cancer surgery - - recurrence, contralateral LN MTS, lung and bone MTS
Skeletal brown tumor accumulate MIBI
Patient preparation for double tracer
Avoid contrast 2 weeks
Withhold thyroid hormone therapy for 2-3 weeks
PTU and methimazole - for 1 week
Planar in 15 min, 2-3h
IV 20 mCi
SPECT/CT
Distinguish inferior from inferior-posterior glands
PET
FDG
C11-methionine - most promising
F-fluorocholine - most promising
FDOPA
