Flashcards in Thyroid Gland Deck (142):
What is the arterial blood supply to the thyroid?
1. Superior thyroid artery (first branch of the external carotid artery)
2. Inferior thyroid artery (branch of the thyrocervical trunk)
What is the venous drainage of the thyroid?
1. Superior thyroid vein
2. Middle thyroid vein
3. Inferior thyroid vein
What is the thyroid lobe appendage coursing toward the hyoid bone from around the thyroid isthmus?
What percentage of patients have a pyramidal thyroid lobe?
What veins do you first see after opening the platysma muscle when performing a thyroidectomy?
Anterior jugular veins
What is the lymph node group around the pyramidal thyroid lobe?
Delphian lymph node group
What is the thyroid isthmus?
Midline tissue border between the left and right thyroid lobes
Which ligament connects the thyroid to the trachea?
Ligament of Berry
What is the IMA artery?
Small inferior artery to the thyroid from the aorta or innominate artery
What percentage of patients have an IMA artery?
What is the most posterior extension of the lateral thyroid lobes?
Tubercle of Zuckerkandl
Which paired nerves must be carefully identified during a thyroidectomy?
Recurrent laryngeal nerves, which are found in the tracheoesophageal grooves and dive behind the cricothyroid muscle.
Damage to these nerves paralyzes laryngeal abductors and causes hoarseness if unilateral, and airway obstruction if bilateral
What nerve (other than the recurrent laryngeal nerves) is at risk during a thyroidectomy and what are the symptoms?
Superior laryngeal nerve.
If damaged, patient will have a deeper and quieter voice.
What is TRH?
Released from the hypothalamus; causes release of TSH
What is TSH?
Released by the anterior pituitary; causes release of thyroid hormone from the thyroid
What are the thyroid hormones?
T3 and T4
What is the most active form of thyroid hormone?
What is the thyroid negative feedback loop?
T3 and T4 feed back negatively on the anterior pituitary, causing decreased release of TSH in response to TRH
What is the most common site of conversion of T4 to T3?
Peripheral (e.g. liver)
What is Synthroid (levothyroxine): T3 or T4?
What is the half-life of Synthroid (levothyroxine)?
What do parafollicular cells secrete?
What percentage of people have a thyroid nodule?
What is the differential diagnosis of a thyroid nodule?
Multinodular goiter, adenoma, hyperfunctioning adenoma, cyst, thyroiditis, carcinoma, lymphoma, parathyroid carcinoma
What are 3 types of non-thyroidal neck masses?
1. Inflammatory lesions (e.g. abscess, lymphadenitis)
2. Congenital lesions (e.g. thryoglossal duct, branchial cleft cyst)
3. Malignant lesions (e.g. lymphoma, metastases, squamous cell carcinoma)
What studies can be used to evaluate a thyroid nodule?
U/S (solid or cystic); FNA (cytology); I scintiscan (hot or cold)
What is the diagnostic test of choice for a thyroid nodule?
What is the percentage of false negative results on FNA for thyroid nodule?
What is meant by a hot vs. cold nodule?
Nodule uptake of IV I-123 or mT-99:
Hot: increased I-123 uptake = functioning or hyperfunctioning nodule
Cold: decreased I-123 uptake = nonfunctioning nodule
What are the indications for a I-123 scintiscan?
1. Nodule with multiple non-diagnostic FNAs with low TSH
2. Nodule with thyrotoxicosis and low TSH
What is the role of thyroid suppression of a thyroid nodule?
Diagnostic and therapeutic (administration of thyroid hormone suppresses TSH secretion, and up to half of the benign thyroid nodules will disappear)
In evaluating a thyroid nodule, which history findings suggest thyroid carcinoma?
1. Neck radiation
2. Family history (thyroid cancer, MEN-II)
3. Young age (especially children)
4. M > F
In evaluating a thyroid nodule, which signs suggest thyroid carcinoma?
1. Single nodule
2. Cold nodule
3. Increased calcitonin levels
5. Hard, immobile nodule
In evaluating a thyroid nodule, which symptoms suggest thyroid carcinoma?
1. Voice change
3. Discomfort (in neck)
4. Rapid enlargement
What is the most common cause of thyroid enlargement?
What are indications for surgery with multinodular goiter?
Cosmetic deformity, compressive symptoms, cannot rule out cancer
What is Plummer's disease?
Toxic multinodular goiter
What percentage of cold thyroid nodules are malignant?
25% in adults
What percentage of multinodular masses are malignant?
What is the treatment of a patient with a history of radiation exposure, thyroid nodule, and negative FNA?
Most experts would remove the nodule surgically
What should be done with thyroid cyst aspirate?
Send to cytopathology
What are the 5 main types of thyroid carcinoma?
1. Papillary carcinoma (80%)
2. Follicular carcinoma (10%)
3. Medullary carcinoma (5%)
4. Hurthle cell carcinoma (4%)
5. Anaplastic carcinoma (1-2%)
What are the signs and symptoms of thyroid carcinoma?
Mass or nodule, LAD (most euthyroid)
What comprises the workup of thyroid carcinoma?
FNA, thyroid U/S, TSH, Ca level, CXR, +/- I-123 scintiscan
What oncogenes are associated with thyroid cancers?
Ras gene family and RET proto-oncogene
What is the most common thyroid cancer?
What is the environmental risk factor for papillary carcinoma?
What is the average age for papillary thyroid carcinoma?
What is the sex distribution for papillary thyroid carcinoma?
M:F = 1:2
What are the associated histologic findings with papillary thyroid carcinoma?
What is the route and rate of spread of papillary thyroid carcinoma?
Most spread slowly via lymphatics (cervical adenopathy)
What is the I-131 uptake by papillary thyroid carcinoma?
What is the 10-year survival rate for papillary thyroid carcinoma?
What is the treatment for a papillary thyroid tumor < 1.5 cm with no history of neck radiation exposure?
1. Thyroid lobectomy and isthmectomy
2. Near-total thyroidectomy
3. Total thyroidectomy
What is the treatment for a papillary thyroid tumor > 1.5 cm, bilateral, positive cervical node metastasis, or a history of radiation exposure?
What is the treatment for lateral palpable cervical lymph nodes in papillary thyroid carcinoma?
Modified neck dissection (ipsilateral)
What is the treatment for central palpable cervical lymph nodes in papillary thyroid carcinoma?
Central neck dissection
Do positive cervical nodes affect the prognosis for in papillary thyroid carcinoma?
What is a lateral aberrant thyroid in papillary cancer?
Misnomer (it is metastatic papillary carcinoma to a lymph node)
What postoperative medication should be administered for papillary thyroid carcinoma?
Thyroid hormone replacement, to suppress TSH
What is a postoperative treatment option for in papillary thyroid carcinoma?
Postoperative I-131 scan can locate residual tumor and distant metastasis that can be treated with ablative doses of I-131
What is the most common site of distant metastases of papillary thyroid carcinoma?
What are the P's of papillary thyroid cancer?
Popular (most common)
Palpable lymph nodes
Positive I-131 uptake
Postoperative I-131 scan to diagnose metastases
What is the nodular consistency in follicular thyroid carcinoma?
What is the route of spread for follicular thyroid carcinoma?
Hematogenous, more aggressive than papillary carcinoma
What is the male:female ratio for follicular thyroid carcinoma?
What is the I-131 uptake by follicular thyroid carcinoma?
What is the overall 10-year survival rate for follicular thyroid carcinoma?
Can the diagnosis of follicular thyroid carcinoma be made by FNA?
No (tissue structure is needed for a diagnosis of cancer)
What histologic findings define malignancy in follicular thyroid carcinoma?
Capsular or blood vessel invasion
What is the most common site of distant metastasis for follicular thyroid carcinoma?
What is the treatment for follicular thyroid carcinoma?
What is the postoperative treatment option for malignant follicular thyroid carcinoma?
Postoperative I-131 scan for diagnosis/treatment
What are the 4 F's of follicular thyroid carcinoma?
Follicular thyroid carcinoma
Far-away metastasis (spread hematogenously)
What is Hurthle cell thyroid cancer?
Thyroid cancer of the Hurthle cells
What is the cell of origin in Hurthle cell thyroid cancer?
What is the I-131 uptake in Hurthle cell thyroid cancer?
How is the diagnosis of Hurthle cell thyroid cancer made?
FNA can identify cells, but malignancy can be determined only by tissue histology
What is the route of metastasis in Hurthle cell thyroid cancer?
Lymphatic > hematogenous
What is the treatment for Hurthle cell thyroid cancer?
What is the 10-year survival rate for Hurthle cell thyroid cancer?
With what conditions is medullary thyroid cancer associated?
What is the histology of medullary thyroid cancer?
What does a medullary thyroid tumor secrete?
What is the appropriate stimulation test for medullary thyroid cancer?
Pentagastrin (causes an increase in calcitonin)
What is the route of spread in medullary thyroid cancer?
Lymphatic and hematogenous distant metastasis
How is the diagnosis of medullary thyroid cancer made?
What is the I-131 uptake in medullary thyroid cancer?
What is the associated genetic mutation in medullary thyroid cancer?
What is the male:female ratio with medullary thyroid cancer?
What is the 10-year survival rate for medullary thyroid cancer?
Without LN involvement: 80%
With LN spread: 45%
What should all patients with medullary thyroid cancer also be screened for?
MEN-II: pheochromocytoma, hyperparathyroidism
If medullary thyroid cancer and pheochromocytoma are found, which one is operated on first?
What is the treatment for medullary thyroid cancer?
Total thyroidectomy and median lymph node dissection.
Modified neck dissection, if lateral cervical nodes are positive.
What are the M's of medullary thyroid cancer?
Medullary thyroid cancer:
Median lymph node dissection
Modified neck dissection if lateral nodes are positive
What is anaplastic thyroid carcinoma also known as?
What is anaplastic thyroid carcinoma?
Undifferentiated cancer arising in 75% of previously differentiated thyroid cancers (most commonly, follicular carcinoma)
What is the male:female ratio with anaplastic thyroid carcinoma?
F > M
What are the associated histologic findings with anaplastic thyroid carcinoma?
Giant cells, spindle cells
What is the I-131 uptake in anaplastic thyroid carcinoma?
Very poor uptake
How is the diagnosis of anaplastic thyroid carcinoma made?
What is the major differential diagnosis for anaplastic thyroid carcinoma?
What is the treatment of small anaplastic thyroid tumors?
Total thyroidectomy, XRT/chemotherapy
What is the treatment for anaplastic thyroid carcinoma with airway compromise?
Debulking surgery and tracheostomy, XRT/chemotherapy
What is the prognosis for anaplastic thyroid carcinoma?
Dismal, most patients are stage IV
What laboratory value must be followed postoperatively after a thyroidectomy?
Calcium (decrease secondary to parathyroid damage; during lobectomy, the parathyroids must be spared and their blood supply protected; if blood supply is compromised intra-operatively, they can be autografted into the SCM or forearm)
What is the differential diagnosis of postoperative dyspnea after a thyroidectomy?
Neck hematoma (remove sutures and clot at the bedside); Bilateral recurrent laryngeal nerve damage
What is a lateral aberrant rest of the thyroid?
Misnomer: it is a papillary cancer of a lymph node from metastasis
What is the most common cause of hyperthyroidism?
What is Graves' disease?
Diffuse goiter with hyperthyroidism, exophthalmos, and pretibial myxedema
What is the etiology of Graves' disease?
Caused by circulating antibodies that stimulate TSH receptors on follicular cells of the thyroid and cause deregulated production of thyroid hormones
What is the male:female ratio for Graves' disease?
What specific physical exam finding is associated with Graves' disease?
How is the diagnosis of Graves' disease made?
Increased T3,T4 and anti-TSH receptor antibodies, decreased TSH, global uptake of I-131 radionuclide
What are treatment option modalities for Graves' disease?
1. Medical blockade (iodide, propranolol, PTU, methimazole, Lugol's solution)
2. Radioiodide ablation (most popular)
3. Surgical resection (bilateral subtotal thyroidectomy)
What are the possible indications for surgical resection in Graves' disease?
If patient is noncompliant or refractory to medicines, pregnant, a child, or if patient refuses radioiodide therapy.
What is the major complication of radioiodide or surgery for Graves' disease?
What does PTU stand for?
How does PTU work?
1. Inhibits incorporation of iodine into T4/T3 (by blocking peroxidase oxidation of iodide to iodine)
2. Inhibits peripheral conversion of T4 to T3
How does methimazole work?
Inhibits incorporation of iodine into T4/T3 only (by blocking peroxidase oxidation of iodide to iodine)
What is toxic multinodular goiter also known as?
What is toxic multinodular goiter?
Multiple thyroid nodules with one or more nodules producing thyroid hormone, resulting in hyperfunctioning thyroid
What medications may bring on hyperthyroidism with a multinodular goiter?
Amiodarone (or any iodine-containing medication or contrast)
How the hyperfunctioning nodule localized?
I-131 radionuclide scan
What is the treatment for toxic multinodular goiter?
Surgically remove hyperfunctioning nodule(s) with lobectomy or near total thyroidectomy
What is Pemberton's sign?
Large goiter causes plethora of head with raising of both arms
What are the features of acute thyroiditis?
Painful, swollen thyroid, fever, overlying skin erythema, dysphagia
What is the cause of acute thyroiditis?
Bacteria (usually Staph or Strep), usually caused by a thyroglossal fistula or anatomic variant
What is the treatment of acute thyroiditis?
Antibiotics, drainage of abscess, needle aspiration for culture.
Most patients need definitive surgery later to remove the fistula.
What are the features of subacute thyroiditis?
Glandular swelling, tenderness, often follows URI, elevated ESR
What is the cause of subacute thyroiditis?
What is the treatment of subacute thyroiditis?
Supportive (NSAIDs, +/- steroids)
What is De Quervain's thyroiditis?
Another name for subacute thyroiditis caused by a virus
What are the common causative bacteria in acute suppurative thyroiditis?
Streptococcus or Staphylococcus
What are the two types of chronic thyroiditis?
1. Hashimoto's thyroiditis
2. Riedel's thyroiditis
What are the features of Hashimoto's thyroiditis?
Firm and rubbery gland, 95% in women, lymphocyte invasion
What is the most common cause of hypothyroidism in the US?
What is the etiology of Hashimoto's disease?
What lab tests should be performed to diagnose Hashimoto's disease?
Antithyroglobulin and microsomal antibodies
What is the medical treatment for Hashimoto's thyroiditis?
Thyroid hormone replacement if hypothyroid (surgery is reserved for compressive symptoms and/or if cancer needs to be ruled out)
What is Riedel's thyroiditis?
Benign inflammatory thyroid enlargement with fibrosis of thyroid.
Patients present with painless, large thyroid, which may involve other tissue.