CHAPTER 22- THYROID.txt

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CHAPTER 22- THYROID.txt
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  1. Where is the thyroid from?
    1st and 2nd pharyngeal pouches
  2. Thyrotropin-releasing factor (TRF)
    • 1) released from the hypothalamus
    • 2) acts on the anterior pituitary gland and causes release of TSH
  3. Thyroid-stimulating hormone (TSH)
    • 1) released from the anterior pituitary gland
    • 2) acts on the thyroid gland to release T3 + T4 (through a mechanism that involves cAMP)
    • 3) TRF + TSH release are controlled by T3 and T4 through a negative feedback loop
  4. Superior thyroid artery
    1st branch off external carotid artery
  5. Inferior thyroid artery
    • 1) off thyrocervical trunk
    • 2) supplies inferior and superior parathyroids
    • 3) ligate close to the thyroid to avoid injury to parathyroid glands with thyroidectomy
  6. IMA artery
    occurs in 1%, arises from the innominate or aorta and goes to the isthmus
  7. Superior and middle thyroid veins:
    drain into internal jugular vein
  8. Inferior thyroid vein
    drains into the innominate vein
  9. non-recurrent laryngeal nerve
    1) in 2-3%, more common on the right
  10. Superior laryngeal nerve
    • 1) motor to cricothyroid muscle
    • 2) runs lateral to thyroid lobes
    • 3) tracks close to superior thyroid artery but is variable
    • 4) injury results in loss of projection and easy voice fatigability (opera singers)
  11. Recurrent laryngeal nerves (RLNs)
    • 1) motor to all of the larynx except the cricothyroid muscle
    • 2) runs posterior to thyroid lobes in the tracheoesophageal groove
    • 3) can track with the inferior thyroid artery but are variable
    • 4) left RLN loops around aorta; right RLN loops around right subclavian (or innominate) artery
    • 5) injury results in hoarseness, bilateral injury can obstruct airway --> needs emergency tracheostomy
    • 6) the right nerve is more likely not to be recurrent compared with the left
    • 7) risk of injury for nonrecurrent laryngeal nerve injury during thyroid surgery
  12. Ligament of Berry
    posterior medial suspensory ligament close to RLNs; careful dissection
  13. Thyroglobulin
    • 1) stores T3 and T4 in colloid
    • 2) plasma T4:T3 ratio is 15:1; T3 more active form (is tyrosine + iodine)
    • 3) most T3 produced in periphery by T4 to T3 conversion by peroxidases
  14. What do peroxidases do?
    Peroxidases link (or seperate) tyrosine and iodine
  15. Thyroid-binding globulin
    • 1) thyroid hormone transport
    • 2) T3 +T4 also bind albumin
  16. What is the most sensitive indicator of thyroid gland function?
    TSH
  17. Tubercles of Zuckerkandl
    • 1) most lateral, posterior extension of thyroid tissue
    • 2) rotate medially to find RLNs
    • 3) this portion is left behind with subtotal thyroidectomy because of proximity to RLNs
  18. Parafollicular C-cells:
    produce calcitonin
  19. Resin T3 uptake
    • 1) measures free T3 by having it bind resin
    • 2) increased resin uptake --> hyperthyroidism or decreased TBG
    • 3) decreased resin uptake --> hypothyroidism or increased TBG
  20. thyroxine treatment
    • 1) TSH levels should fall to 50%
    • 2) osteoporosis is a long term side effect
  21. Postthyroidectomy stridor
    open neck and remove hematoma emergently--> can result in airway compromise
  22. Thyroid storm
    • 1) Symptoms:
    • 1- increased HR
    • 2- fever
    • 3- numbness
    • 4- irritability
    • 5- vomiting
    • 6- diarrhea
    • 7- high output cardiac failure (most common cause of death)

    • 2) most common after surgery in patient with undiagnosed Graves Disease
    • 3) can also be precipitated by:
    • 1- anxiety
    • 2- adrenergic stimulants
    • 3- excessive palpation of the gland
    • 4) Tx:
    • 1- beta-blockers
    • 2- PTU
    • 3- lugol's solution (KI)
    • 4- cooling blankets, oxygen, glucose,fluid
    • - emergent thyroidectomy rarely indicated
  23. Wolff-Chaikoff effect
    • 1) very effective for patients in thyroid storm
    • 2) patient given high doses of iodine (lugol's solution, potassium iodide), which inhibits TSH action on thyroid and inhibits organic coupling of iodide, resulting in less T3 + T4 release
  24. Asymptomatic thyroid nodule
    • 1st- Thyroid function tests
    • 1-if elevated, give thyroxine; nodule should regress within 6 months
    • 2- if not elevated, proceed with fine-needle aspiration (FNA)

    • 2nd- FNA
    • A) Determinant in 75-90%--> follow appropriate treatment
    • 1- shows follicular cells--> thyroidectomy or lobectomy (5-10% malignancy risk)
    • 2- shows thyroid Ca--> thyroidectomy or lobectomy and appropriate treatment
    • 3- shows cyst fluid --> drain fluid (if recurs, thyroidectomy/lobectomy)
    • 4- shows colloid tissue--> most likely colloid goiter; low chance of malignancy (<1%); tx: thyroxine, thyroidectomy/lobectomy if enlarges)

    • B) Indeterminant in 10-25% --> get radionuclide study
    • 1- hot nodule--> thyroxine for 6 months; if size does not decrease, perform lobectomy
    • 2- cold nodule-->
    • 1) thyroidectomy or lobectomy (more likely malignant than hot nodule)
    • 2) 85% of thyroid nodules are bengin
    • 3) thyroid nodules have female predominance
  25. Goiter
    • 1) any abnormal enlargement
    • 2) most identifiable cause is iodine deficiency
    • 3) Tx: iodine replacement
    • 4) diffuse enlargement without evidence of functional abnormality= nontoxic colloid goiter
    • 1- tx: try to suppress with thyroxine, 131I (may be ineffective), thioamides, subtotal thyroidectomy, or lobectomy on side of goiter if medical treatment ineffective
  26. Substernal goiter
    • 1) usually secondary (vessels originate from superior and inferior thyroid arteries
    • 2) primary substernal goiter- rare (vessels originate from innominate artery)
    • 1- Tx: try to suppress with thyroxine, 131I (may be ineffective), thioamides, subtotal thyroidectomy/lobectomy on each side of goiter if medical treatment ineffective
  27. Mediastinal thyroid tissue
    most likely from acquired disease with inferior extensions of a normally placed gland
  28. Abnormalities of thyroid descent:
    Pyramidal lobe- occurs in 10%, extends from isthmus toward the thymus

    • Lingual thyroid:
    • 1) thyroid tissue that persists in the area of the foramen cecum at the base of the tongue
    • 2) symptoms: dysphagia, dyspnea, dysphonia
    • 3) 2% malignancy risk
    • 4) Tx: thyroxin suppression; abolish with 131I or resection if it is enlarged or suggestive of cancer, or if it does not shrink after medical therapy
    • 5) is the only thyroid tissue in 70% of patients who have it

    • Thyroglossal duct cyst
    • 1) classically moves upward with swallowing
    • 2) susceptible to infection and may be premalignant
    • 3) Tx: resection--> need to take midportion or all of hyoid bone along with the thyroglossal duct cyst
  29. Propylthiouracil (PTU) and methimazole
    • 1) Good for:
    • 1- young patients
    • 2- small goiters
    • 3- mild T3/T4 elevation

    • PTU (thioamides)
    • 1- Inhibits peroxidases and prevents DIT and MIT coupling
    • 2- Side effects: aplastic anemia or agranulocytosis (rare)

    • Methimazole
    • 1- inhibits peroxidases and prevents DIT and MIT coupling
    • 2- side effects: cretinism in newborns (crosses placenta) and aplastic anemia or agranulocystosis
  30. Radioactive Iodine (I131)
    • 1) good for patients who are poor surgical risks or unresponsibe to PTU
    • 2) Radioactive iodine should not be used in children or during pregnancy--> can traverse the placenta
  31. Thyroidectomy
    • Good for:
    • 1- large glands
    • 2- cold nodules in toxic glands
    • 3- toxic multinodular goiters not responsive to medical therapy
    • 4- toxic adenomas not responsive to medical therapy
    • 5- pregnant patients not controlled with medical therapy

    2) Best time to operate is 2nd trimester (decreased risk of teratogenic events and premature labor)

    3) subtotal thyroidectomy can leave patient euthyroid
  32. Graves Disease:
    • 1) toxic diffuse goiter
    • 2) Associated with:
    • 1- women
    • 2- expothalmos
    • 3- pretibial edema
    • 4- atrial fibrillation
    • 5- heart dysfunction
    • 6- heat intolerance
    • 7- thirst
    • 8- increased appetite
    • 9- weight loss
    • 10- sweating + palpitations
    • 2) Graves is the most common cause of hyperthyroidism (80%)
    • 3) caused by IgG antibodies to TSH receptor (long-acting thyroid stimulator, thyroid-stimulating immunoglobulin)
    • 4) if large, can get cervical compression syndromes
    • 5) Dx:
    • 1- high 123I uptake (thyroid scan) diffusely in thyrotoxic patient with goiter
    • 2- LATS level
    • 3- decreased TSH
    • 4- increased T3/T4
    • 6) Tx:
    • 1- thioamides (70% recurrence)
    • 2- 131I (10% recurrence)
    • 3- subtotal thyroidectomy (10% recurrence)
    • 4- total thyroidectomy with thyroxine replacement if medical therapy fails
    • 7) medical therapy usually manages hyperthyroidism
    • 8) Unusual to have to operate on these patients unless in setting of suspicious nodule
    • 9) preop preperation:
    • 1- PTU or methimazole until euthyroid
    • 2- beta-blocker
    • 3- 1 week before surgery, lugol's solution for 10-15 days to decrease friability and vascularity (start only after euthyroid).
    • 10) Operation: bilateral subtotal or total thyroidectomy
    • 11) Indications for surgery:
    • 1- noncompliant patient
    • 2- recurrence after medical therapy
    • 3- children
    • 4- pregnant women not controlled with medical therapy
    • 5- concomitant suspicious thyroid nodule
  33. Toxic multinodular goiter:
    • 1) most common cause of thyroid enlargement
    • 2) women, age >50 years, normal thyroid function tests
    • 3) Symptoms:
    • 1- cardiac symptoms
    • 2- weight loss
    • 3- insomnia
    • 4- airway compromise
    • 5- symptoms can be precipitated by contrast dyes
    • 4) usually nontoxic 1st
    • 5) caused by hyperplasia secondary to chronic low-grade TSH stimulation
    • 6) Tx:
    • 1- 131I and thoamides; 131I can be less effective in some (inhomogenous uptake by gland)
    • 2- subtotal thyroidectomy if medical treatment ineffective
    • 3- unusual to have to operate on these patients unless in setting of suspicious nodule
  34. Single toxic nodule
    • 1) women; younger, can cause cervical compression
    • 2) >3 cm usually symptomatic
    • 3) Dx: thyroid scan
    • 4) 20% of hot nodules eventually cause symptoms
    • 5) thought to function autonomously
    • 6) Tx:
    • 1- 131I and thioamides
    • 2- lobectomy if medical treatment ineffective
  35. Rare causes of hyperthyroidism
    • 1) trophoblastic tumors
    • 2) TSH-secreting pituitary tumors
  36. Hashimoto's disease
    • 1) most common cause of hypothyroidism in adults
    • 2) Enlarged gland, painless, chronic thyroiditis
    • 3) Women; history of childhood XRT
    • 4) can cause thyrotoxicosis in the acute early stage
    • 5) caused by both humeral and cell-mediated autoimmune disease (microsomal and thyroglobulin antibodies)
    • 6) Goiter secondary to lack of organification of trapped iodide inside gland
    • 7) pathology shows lymphocytic infiltrate
    • 8) Tx: thyroxine 1st line; partial thyroidectomy if continues to grow despite thyroxine, if nodules appear, or compression symptoms occur
    • 9) frequently no surgery is necessary for Hashimoto's disease
  37. Bacterial thyroiditis (rare)
    • 1) usually secondary to contiguous spread
    • 2) normal thyroid function tests, fever, dysphagia, tenderness
    • 3) upper respiratory tract infection (URI) symptoms most common precursor (staph/strep)
    • 4)Tx: antibiotics
    • 1- may need lobectomy to rule out cancer in patients with unilateral swelling and tenderness
    • 2- may need thyroidectomy for persistent inflammation
  38. De Quervain's thyroiditis
    • 1) can be associated with hyperthyroidism initially
    • 2) Viral URI, tender thyroid, sore throat, mass, weakness, fatigue
    • 3) more common in women
    • 4) elevated ESR
    • 5) Tx: steroids + ASA
    • 1- may need lobectomy to rule out cancer in patients with unilateral swelling and tenderness
    • 2- may need total thyroidectomy for persistent inflammation
  39. Riedel's fibrous struma
    • 1) woody, fibrous component that can involve adjacent strap muscles and carotid sheath
    • 2) can resemble thyroid cancer or lymphoma (need biopsy)
    • 3) disease frequently results in hypothyroism and compression symptoms
    • 4) associated with:
    • 1- sclerosing cholangitis
    • 2- fibrotic diseases
    • 3- methysergide treatment
    • 4- retroperitoneal fibrosis
    • 5)Tx:
    • 1- steroids and thyroxine
    • 2- may need isthmectomy or tracheostomy
    • 3- if resection needed, watch for RLNs
  40. Thyroid Cancer
    • 1) most common endocrine malignancy in the United States
    • 2) Follicular cells on FNA
    • 1- 5-10% chance of malignancy (unable to differentiate between follicular cell adenoma, follicular cell hyperplasia, normal thyroid tissue, andd follicular cell Ca on FNA)
    • 3) Worrisome for malignancy:
    • 1- solid
    • 2- solitary
    • 3- cold
    • 4- slow growing
    • 5- hard
    • 6- male
    • 7- age >50
    • 8- previous neck XRT
    • 9- MEN IIa or IIb
    • 4) sudden growth- could be hemorrhage into previously undetected nodule or malignancy
    • 5) patients can also present with voice changes and dysphagia
  41. Thyroid adenomas
    need to be differentiated from carcinomas--> require lobectomy
  42. Follicular adenomas
    • 1) colloid, embryonal, fetal--> no increase in cancer risk
    • 2) still need lobectomy to prove it is adenoma
  43. Papillary thyroid carcinoma
    • 1) most common (80-90%) thyroid Ca
    • 2) least aggressive, slow growing, has the best prognosis
    • 3) young adults, women, children
    • 4) Risk factors: childhood XRT (very inc. risk)--> most common tumor following neck XRT
    • 5) older age (>45-50) predicts a worse prognosis
    • 6) lymphatic spread 1st, but is not prognostic
    • 7) prognosis is based on local invasion
    • 8) rare metastases- lung most common
    • 9) Children are more likely to be node positive (70-80%) than are adults (10-20%)
    • 10) large, firm nodules in children are worrisome
    • 11) many are multicentric
    • 12) pathology- psammoma bodies (calcium) and orphan annie nuclei
    • 13) Treatment:
    • 1- minimal/incidental (<1cm)--> lobectomy
    • 2- Total thyroidectomy for:
    • 1- bilateral lesions
    • 2- multicentricity
    • 3- history of XRT
    • 4- positive margins
    • 5- tumors >1cm
    • 3) clinically positive cervical nodes- need ipsilateral MRND
    • 4) Extrathyroidal tissue involvement- need ipsilateral MRND
    • 5) 131I 6 weeks after surgery when:
    • 1- metastatic disease
    • 2- residual local disease
    • 3- positive lymph nodes
    • 4- capsular invasion
    • 6) XRT only for unresectable disease not responsive to 131I
    • 7) do not give thyroid replacement until after treatment with 131I--> will suppress uptake
    • 8) 95% 5-year survival rate; death secondary to local disease
    • 9) enlarged lateral neck lymph node that shows normal appearing thyroid tisse is papillary thyroid Ca with lymphatic spread.
    • Tx: total thyroidectomy and MRND
  44. Follicular thyroid carcinoma
    • 1) hematogenous spread (bone most common)--> 50% have metastatic disease at the time of presentation
    • 2) more aggressive than thyroid papillary cell cancer
    • 3) older adults (50-60s), women
    • 4) FNA shows just follicular cells- 10% chance of malignancy; need thyroidectomy
    • 5) Tx:
    • 1- lobectomy--> if pathology shows adenoma or follicular cell hyperplasia nothing else needed
    • 2- If follicular Ca- total thyroidectomy for lesions >1cm or extrathyroidal disease
    • 3- clinically positive cervical nodes- need ipsilateral MRND
    • 4- extrathyroidal tissue involvement- need ipsilateral MRND
    • 5- patients with lesions >1cm or extrathyroidal disease (or capsular invasion)- 131I 6 weeks after surgery
    • 6- if microinvasive (<1cm), has rare nodal spread (<10%), and is usually incidental finding on pathology--> as long as margins are negative, lobectomy is probably all that is needed
    • 7- 70% 5-year survival rate; prognosis based on stage
  45. Medullary thyroid carcinoma
    • 1) can be associated with MEN IIa or IIb
    • 2) usually the 1st manifestation of MEN IIa and IIb
    • 3) tumor arises from parafollicular C cells (which secrete calcitonin)
    • 4) C-cell hyperplasia is considered premalignant
    • 5) pathology- shows amyloid deposition
    • 6) gastrin can be used to test for medullary thyroid Ca--> causes increase in calcitonin
    • 7) calcitonin- can cause flushing and diarrhea
    • 8) need to screen for hyperparathyroidism and pheochromocytoma
    • 9) lymphatic spread- most have involved nodes at time of diagnosis
    • 10) early metastases to lung, liver, and bone
    • 11) Tx:
    • 1- total thyroidectomy with central node dissection
    • 2- MRND if patient has clnically positive nodes (bilateral MRND if both lobes have tumor) or extrathyroidal disease present
    • 3- prophylactic thyroidectomy and central node dissection in MEN IIa or IIb patients at age 2
    • 4- liver and bone metastases prevent attempt at cure
    • 5- XRT may be useful for unresectable local and distant metastatic disease
    • 6- may be useful to monitor calcitonin levels for disease recurrence
    • 7- more aggressive than follicular and papillary Ca
    • 8- 50% 5-year survival rate; prognosis based on presence of regional and distant metastases
  46. Hurthle cell carcinoma
    • 1) most are benign (hurthle cell adenoma); presents in older patients
    • 2) early nodal spread if malignant
    • 3) metastases go to bone and lung
    • 4) Tx: total thyroidectomy; MRND for clinically positive nodes
  47. Anaplastic thyroid cancer:
    • 1) elderly patients with long-standing goiters
    • 2) most aggressive thyroid cancer
    • 3) rapidly lethal (0% 5 yr survival rate); usually beyond surgical management by diagnosis
    • 4) Tx: total thyroidectomy for the rare lesion that can be resected
    • 5) can peform palliative thyroidectomy for compressive symptoms or give palliative chemotherapy or XRT
  48. For which thyroid cancer is XRT effective?
    • 1) papillary
    • 2) follicular
    • 3) medullary
    • 4) Hurthle cell
  49. 131I is effective for:
    • 1) papillary and follicular thyroid Ca only
    • 2) can cure bone and lung metastases
    • 3) done 6 weeks after surgery
  50. Indications for 131I:
    • 1) recurrent thyroid papillary or follicular Ca
    • 2) primary inoperable tumors due to local invasion
    • 3) papillary thyroid Ca with extrathyroidal disease
    • 4) follicular thyroid Ca >1cm or with extrathyroidal disease
    • 5) patients with papillary of follicular cell Ca with metatstases--> need to perform total thyroidectomy to facilitate uptake of 131I to the metastatic lesions
  51. Side effects of 131I:
    • 1) sialoadentitis
    • 2) GI symptoms
    • 3) infertility
    • 4) bone marrow suppression
    • 5) parathyroid dysfunction
    • 6) leukemia
  52. When is TSH level highest in relation to a thyroidectomy:
    TSH level highest 4-6 weeks after thyroidectomy- best time for 131I scan for metastatic disease
  53. What can help suppress TSH and slow metastatic disease and when should it be administered
    Thyroxine can help suppress TSH and slow metastatic disease. Its administered only after 131I therapy has finished.
  54. Name two things that are very rare causes of thyroid cancer:
    • 1) lymphoma
    • 2) squamous cell carcinoma

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