Endocrinology Flashcards
Where do the superior and inferior parathyroids lie in relation to the RLN?
Superior - DEEP and about 1 cm above crossing of RLN and ITA
Inferior - Superficial to RLN
What is the blood supply to the parathyoids and where does it arise from?
ITA - from the thyrocervical trunk
Course of RLN on right and left?
Right - Loops around subclavian a., courses more LATERAL
Left - Loops around aortic arch, courses more MEDIAL
Both enter posterior to cricothyroid joint
What does RLN innervate?
What does SLN innervate?
RLN - All intrinsic muscles except cricothyroid and all sensory to larynx
SLN - External branch = cricothyroid (Internal branch = sensory, enters via thyrohyoid membrane).
Function of parathyroid hormone?
-Maintain an extracellular concentration of calcium
through the following effects:
-Stimulates osteoclasts
-Increases distal tubular reabsorption of Ca2+
-Decreases Phosphate reabsorption
-Increases production of 1,25 (OH)2 Vit D
Primary hyperparathyroidism Ca2+ levels and PTH levels?
Serum calcium levels > 10.2 mg/dl, in the setting of an elevated PTH level (Normal serum values for PTH are 10 - 55 picograms per milliliter (pg/mL)
*Don’t forget to rule out Familial Hypocalciuric Hypercalcemia (elevated serum calcium, LOW urinary calcium. True hyperparathyroid will have BOTH elevated)
What is deemed acceptable for PTH after adenoma is removed?
PTH should fall at least 50% in cases of successful single adenoma disease (or into normal range), though the half life of PTH is roughly 5-8 minutes it is advised to wait at least 15 to 20 minutes post excision.
Indications for ASYMPTOMATIC primary hyperparathyroidism?
- Serum calcium > 1 mg/dL above upper limit of normal
- Creat clearance reduced by > 60 mL/min (reduced by 30%)
- Age < 50 years
- T score < 2.5 (post menopause and age > 50), Z score < 2.5 (pre menopause, age < 50)
- Patient wants surgery
- 24 urinary calcium > 400 mg/dL
- Ectopic parathyroid
- Parathyroid carcinoma (think if serum ca > 14, high PTH, neck mass)
Where does thyroid develop from and when?
Develops at foramen cecum starting at 5th week.
Treatment for HYPERcalcemia?
LOOP diuretics (thiazides can CAUSE hyperCa2+), bisphosphinates, calcitonin, saline hydration, dialysis, cincalcinet
Location of external branch of SLN in relation to STA?
Usually DORSAL (behind) the STA
Treatment for thyroid storm?
Antithyroid medication (usually PTU), antipyretic (tylenol), steroids, beta blocker, iodine solution, cooling measures.
Primary cells in the parathyroid?
Chief cells (monitor calcium levels and make PTH)
Treatment options for Graves orbitopathy?
Aim is to induce a euthyroid state - antithyroid medication, RAI or surgery. However, do NOT do RAI for active and rapidly progressive orbitopathy due to concern for compressive optic neuropathy.
What percentage of thyroid tumors are comprised of lymphoma and who is at risk?
2-5%, non Hodgkins associated with Hashimotos
Patients with Hashimotos are at increased risk for non-hodgkins lymphoma (hodkins thyroid is very rare).
Sensitivity and specificity of FNA for thyroid?
Both > 90%
How is NPV affected as thyroid tumor size increases and what is recommended for tumors >4 cm?
NPV for tumors > 4 cm is poor. Therefore, for nodules > 4 cm with NEGATIVE FNA, surgery is still recommended (since increased size has increased PPV for being malignant).
Features of MEN1, MEN2A, MEN2B?
MEN1: Pituitary adenoma, Parathyroid hyperplasia, Panreatic tumors (PPP)
MEN2A: Parathyroid hyperplasia, Medullary thyroid carcinoma, Pheochromocytoma (MPP)
MEN2B: Marfinoid, medullary thyroid carcinoma, mucosal neruomas, pheochromocytoma (MMM + P)
What is BRAF mutation specific for in thyroid cancer?
Papillary thyroid cancer - predicts more aggressive course
Thyroid Cancer Staging
T1a T < 1 cm
T1b T > 1 cm, = 2 cm
T2 T > 2 cm, = 4 cm, limited to thyroid
T3 T > 4 cm:
T3a T > 4 cm limited to thyroid
T3b Tumor of any size with ETE into strap muscles
T4 Advanced disease
T4a Moderative advanced disease: ETE into nearby structures of neck
T4b Very advanced disease: ETE toward spine, carotid, prevertebral fascia
N1 Metastasis to regional nodes
N1a Metastasis to level VI or VII. Unilateral or bilateral
N2b Metastasis to lateral neck nodes (levels I – V) or RP nodes. Unilateral or bilateral
M1 Any distant metastasis
What is the mechanism of PTU and Methimazole?
Inhibit T4 to T3 conversion by preventing organification/oxidation of iodine
What stages can a patient < 55 be for thyroid cancer and what is the difference between them?
Can only be stage I or II
I: No distant mets
II: Yes distant mets
What is this histopath and when is it usually seen?
Psamomma bodies, found in papillary thyroid cancer (and meningiomas)
Why do you do thyroid hormone withdrawal or give thyrogen prior to RAI?
TSH stimulates RAI uptake so you either give thyrogen (recombinant humane TSH) or withdraw thyroid hormone to increase TSH! TSH should be elevated to at least 30 mU/L.
What is Levothyroxine? Liothyronine?
Levothyroxine: T4
Liothyronine: T3 (10% of circulating thyroid hormone)
How common is follicular thyroid carcinoma? How does it usually spread?
2nd most common (after papillary thyroid)
Usually hematologic spread, found in iodine deficient areas
Distant mets more common than papillary
Mortality is directly related to recurrence
What are the four pharyngeal POUCH derivitives?
1st: Middle ear + ET
2nd: Palatine tonsils
3rd: Thymus + inferior parathyroids
4th: Superior parathyroids + ultimobranchial body (give rise to thyroid parafollicular c cells –> secrete calcitonin)
Where do the parafollicular c cells arise from and what do they secrete?
From ultimobranchial body (4th pouch), secerete calcitonin
Medullary thyroid cancer - gene, what do you use to monitor, histopath, TX?
-RET gene
-Associated with MEN2A + MEN2B
-Calcitonin secreting
-Stains + on congo red
-RAI does NOT work for this
What is one unique feature about Hurthle cell carcinoma?
Highest rate of distant mets (~30%)
Variants of papillary thyroid cancer, which is most common and least aggressive?
Follicular (most common, least aggressive)
Tall cell –> consider completion
Columnar cell –> consider completion
Indications for radioactive iodine treatment?
Size > 4 cm
Extrathyroidal extension
Distant metastasis
Extensive vascular invasion
Elevated TG levels
Bulky or > 5 positive LNs
For US of thyroid nodal basins, what features are suspicious and need further investigation?
Lymph nodes that have microcalcifications, cystic aspects, peripheral vascularity, hyperechogenicity and ROUND shape are suspicious for metastatic disease and warrant further investigation
