Endocrinology

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Pasha Otolaryngology

embryologic origin thyroid

endoderm between 1st and 2nd branchial arch on floor of pharynx (foramen cecum) invaginates 4th week and descends into mesenchymal tissue

embryologic pathology

athyreosis (rare), ectopic thyroid, thyroglossal duct cyst

inferior and superior parathyroid arteries usually arise from this

inferior thyroid artery (superior parathyroid artery may arise from superior thyroid artery)

blood supply to thyroid isthmus (and where it comes from)

aortic arch or innominate artery -> thyroid ima artery

lymphatic drainage of isthmus and medial lateral lobes
" " of inferior lateral lobes

delphian (prelaryngeal) and digastric
pretracheal and cervical nodes

SLN internal branch parallels __ and then goes through ___. may form ___ __ ___

superior thyroid artery
thyrohyoid membrane
loop of Galen (after anastomosing with sensory branch of RLN)

SLN external branch innervates

cricothyroid muscle

RLN relationship to inferior thyroid artery

near middle 1/3 of gland it crosses posteriorly or superficially to the inferior thyroid artery

describe thyroid hormone synthesis

thyroglobulin is iodinated to form MIT, DIT (mono/di iodotyrosine) which link to form triiodothyronine T3 or thyroxine T4

this is 90% of thyroid output

T4

what is thyroid hormone transported on (protein and %)

TBG thyroxine binding globulin 75%
thyroxine binding pre albumin TBPA 15%
albumin 5%

these organs convert T4 to T3 and rT3 via 5'monodeiodinase

liver, kidneys, muscle

T3 is __ x more active than T4 and binds with higher affinity to TBG

4

propylthiouracil and methimazole belong to this class

thioamides

mechanism of thioamides

blocks conversion of T4 and oxidation and organification of iodine

Wolf-Chaikoff Effect

excess iodine inhibitis thyroid hormone synthesis

this test is more specific for hypo/hyper thyroidism

free T4

this test is most sensitive for hypo/hyperthyroidism

TSH

what does RT3U (resin T3 uptake) measure

binding capacity of existing TBG, increased RT3U suggests decreased total TBG

TBG, total T4, RT3U, free T4 in normal patients

normal, normal, normal, normal

TBG, total T4, RT3U, free T4 in pregnant patients

increased, increased, decreased, normal

TBG, total T4, RT3U, free T4 in liver/renal disease

decreased, decreased, increased, normal

TBG, total T4, RT3U, free T4 in hyperthyroidism

normal, increased, increased, increased

TBG, total T4, RT3U, free T4 in hypothyroidism

normal, decreased, decreased, decreased

false negative rate of FNA

1-10%

this FNA finding suggests nodular or adenomatous goiter

uniform follicular epithelium and abundant colloid

these 2 types of finding may be benign or carcinoma, requires hemithyroidectomy to examine architecture

follicular cells, hurthle cells

hurthle cells associated with this condition

Hashimoto's thyroiditis

99mTc pertechnetate is trapped by these cells

follicular cells

this tracer used to evaluate for metastasis and also for ablation for hyperthyroidism and residual disease

131Iodine

this tracer is expensive, must be delivered daily, testing requires 2 visits at 4 and 24 hrs (shorter half life)

124 Iodine

malignancy rate for hypofunctioning/cold nodule

5-20%

malignancy rate for hyperfunctioning or autonomous functioning "hot" nodule

4%

which staging system to use for papillary/follicular/medually thyroid cancer depends on this criteria

< or > 45yo

papillary/follicular/medually thyroid cancer staging <45yo

stage I - any T, N, M0
stage II - any T, N, M1

T staging for papillary/follicular/medually thyroid cancer

T1 - <2cm
T2 - >2cm, <4cm
T3 - >4cm, minimal extrathyroidal extension
T4
4a - beyond thyroid capsule
4b - prevertebral fascia, carotid, mediastinal vessels

N staging for papillary/follicular/medually thyroid cancer

N0 - no nodes
N1a - delphian or pre/paratracheal LNs
N1b - cervical, superior mediastinal nodes

Staging for papillary/follicular/medually thyroid cancer >45yo

I - T1, N0, M0
II - T1-2, N0, M0
III - T1-3, N0-1a, M0
IVa - T1-4a, N0-1b, M0
IVb - T1-4b, N0-1b, M0
IVc - T1-4b, N0-1b, M1

T staging for anaplastic thyroid cancer

T4a - intrathyroidal/surgically resectable
T4b - extrathyroidal/surgically unresectable

Staging for anaplastic thyroid cancer

IVa - T4a, any N, M0
IVb - T4b, any N, M0
IVc - T4b, any N, M1

thyroid neoplasia - high risk criteria

AMES
age (>41yo men, >51yo women)
metastases
extrathyroidal, major capsular involvement
size (>5cm)

single most significant overall indicator of poor prognosis

distant mets, especially to bone

most common type of benign adenoma

follicular adenoma

most common thyroid cancer and %

papillary, 70-80%

this syndrome is a risk factor for papillary thyroid cancer (PTC)

Gardner's syndrome

histopath for PTC

psamomma bodies (calcific)
Orphan Annie eyes (intranuclear vacuoles)
multicentric
unencapsulated neoplastic cells (ground glass appearance) with fibrovascular stalks

improvement in survival with elective neck dissection in PTC?

no

neck management in PTC?

modified neck dissection for palpable nodes only

may consider lobectomy and isthmusectomy in these patients with PTC

<1cm in younger patients, controversial

follow up in this amount of time for RAI after thyroidectomy for PTC

6 weeks

second most common thyroid cancer and %

follicular carcinoma (FTC), 10%

20-50% of FTC have this type of spread

hematogenous spread with distant metastasis (lymphatic spread rare)

histopath for FTC

unifocal
malignancy differentiated by presence of extracapsular spread, invasion of lymphatics or vasculartor or metastasis
solid, trabecular, or follicular growth patterns

5 year survival for PTC, FTC and FTC with distant mets, and hurthle cell tumor (oncocytic carcinoma)

95% for PTC
70-85% for FTC (20% with distant mets)
50% for hurthle cell (oncocytic carcinoma)

do Hurthle cell tumors take up radioactive iodine?

no, less sensitive to thyroid suppression and diagnostic and therapeutic radioactive iodine therapy

2 types of medullary thyroid cancer (MTC), their prevalence (%), centricity, laterality, which one is worse prognosis

familial (20-25%), multifocal, bilateral
sporadic (70-75%), unifocal, unilateral, worse prognosis

medullary thyroid cancer derived from this cell type

neuroendocrine parafollicular or C-cells (produce calcitonin)

mutation and chromosome for MTC

Ret-3 oncogene, chromosome 10

management for MTC

total thyroidectomy, elective modified neck dissection, medical thyroid suppression therapy

consider this in childhood with positive germline RET mutations

prophylactic thyroidectomy

prognosis for anaplastic carcinoma including median survival

uniformly fatal (2-6 month median)

histopath of anaplastic carcinoma

bizarre cells
giant and spindle cell variation with high mitotic activity, large areas of necrosis, significant infiltration

primary lymphomas of the thyroid are most commonly this type of tumor

non Hodgkin B cell tumors

primary lymphoma of the thyroid associated with these conditions

chronic lymphocytic thyroiditis, Hashimoto's thyoiditis

MEN I, II (2a), III (2b)

MEN I (Werner's) - PPP pituitary adenoma, pancreatic tumors, parathyroid hyperplasia
MEN II (Sipple's) - MPP medullary thyroid cancer, pheochromocytoma, parathyroid hyperplasia
MEN III (2b) - MPMM medullary thyroid cancer, pheochromocytoma, mucosal neuromas, marfanoid habitus

may consider prior to thyroidectomy to reduce vascularity of gland

Lugol's solution (potassium iodine)

indications for thyroidectomy

suspicion of malignancy
mediastinal extension
compression symptoms (airway compromise, dysphagia)
cosmesis
failed medical management Grave's or hyperthyroidism
pregnancy in Grave's or Hashimoto's thyroiditis
documented metastasis from thyroid carcinoma

Rx for respiratory distress from postop hematoma

immediately remove sutures and open wound

mortality rate from thyroid storm

20-50%

Rx thyroid storm

inorganic iodine
PTU (propylthiouracil)
propranolol
corticosteroids
supportive measures (glucose containing IVF, cooling blanket, O2, antipyretics), ICU admission for cardiac monitoring

another name for toxic nodular goiter

Plummer's disease

PPx Grave's disease

thyroid stimulating immunoglobulins (TSIs) stimulate glandular hyperplasia via TSH receptor -> goiter and increased T3, T4 secretion

risks for graves

radiation exposure, women (adolesence or 30-40yo), genetic disposition

SSx grave's

exophthalmos (autoimmune - T cell - retrobulbar fibroblast interaction which has Ag similar to TSH receptor, secrete GAGs, collagen deposition. previously thought to be extraocular muscle deposition)
diffuse goiter, hyperthyroid symptoms, infiltrative dermopathy

these types of thyroiditis can be painful

subacute granulomatous thyroiditis (de Quervain's)
acute suppurative

another name for Hashimoto's thyoiditis

chronic autoimmune

PPx Hashimoto's

antithyroglobulin and antimicrosomal antibodies -> TSH receptor -> transient hyper, then hypothyoidism

Dx Hashimoto's

antithyroid peroxidase (antimicrosomal ABs, anti-TPO, and anti-Tg)
ESR, TFT, FNA for suspicious nodules

thyroid fibrosis of unknown origin, rock hard thyroid, local pressure, hypothyroidism

Riedel's thyroiditis

these parthyroids have a more variable location

inferior (generally 1-2cm from entrance of inferior thyroid artery to lower thyroid pole)
superior paras - 1cm above intersection RLN with inferior thyroid artery

parathyroid embryology

third dorsal branchial pouch ->inferior paras and thymus
fourth dorsal branchial pouch -> superior paras and C-cells of thyroid

embryologic pathology of parathyroids

supernumeray parathyroids
aberrant parathyroids (most commonly at anterior superior mediastinum)

action of parathyroid hormone (PTH)

increases serum calcium, decreases phosphate by stimulating osteoclastic resorption from bone, increasing Ca absorption in kidney, activating 25-hydroxyvitamin D to 1,25 dihydroxyvitamin D, increasing phosphate excretion

causes of hypercalcemia

CHIMPANZEES
Calcium (exogenous)
Hyperparathyroidism
Immobility
Metastases to bone
Paget's disease
Addison's disease
Neoplasia (solid tumors prostate, lung, colon, breast)
Zollinger Ellison (hypergastrinemia)
Endocrine (familial hypocalciuric hypercalcemia, hyperthyroidism, pheochromocytoma)
Exogenous (excess vit A, D, thiazides, lithium, estrogens, milk-alkali syndrome)
Sarcoidosis (also other granulomatous disease TB, berylliosis)

SSx hypercalcemia/hyperparathyroidism

stones, bones, psychiatric overtones
nephrolithiasis, cholelithiasis
osteitis fibrosa cystica
confusion

medical management hypercalcemia

saline diuresis
bisphosphonates
plicamycin
calcitonin
glucocorticoids
gallium
hemodialysis

most common cause of secondary hyperparthyroidism

chronic renal disease

how does thallium technetium subtraction scan work? sensitivity?

thallium taken up by thyroid + paras
technetium taken up by thyroid only
90%

indications for parathyroidectomy

symptomatic hyperaparathyroidism (bone pain, pathologic fractures, ectopic calcifications, intractable itching)
persistently elevated serum calcium

radioguided parathyroidectomy - how it works

tracer injected 1.5-2 hrs prior to surgery, gamma probe to identify abnormal gland

SSx hypoparathyroidism and hypocalcemia

tetany or neuromuscular excitability
Chvostek's sign
Trousseau's sign

DiGeorge embryology

congenital abnormality of third and fourth branchial pouches, agenesis of parathyroid glands, may have athymia

pseudohypoparathyroidism etiology

end organ resistance to effects of PTH

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