Test Taking Tips
1. Aldosterone and related electrolyte and acid-base imbalances in adrenal disease are popular testing topics.
2. The MEN syndromes are also a favorite topic. Know these well and understand when to operate and what operation to perform!
EMBRYOLOGY, ANATOMY, AND PHYSIOLOGY
What embryologic structures does the thyroid originate from?
The medial thyroid comes from the first and second pharyngeal pouches
Lateral portions of the thyroid and parafollicular C cells arise from the fourth and fifth pharyngeal pouches
FIGURE 12-1. Anatomy of the thyroid gland and surrounding structures, viewed anteriorly. a., artery; n., nerve; v., vein. (Reproduced from Brunicardi FC, Andersen DK, Billiar TR, et al. Schwartz’s Principles of Surgery. 9th ed. www.accessmedicine.com. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.)
Superior thyroid artery (from external carotid artery)
Inferior thyroid artery (from thyrocervical trunk)
What is the venous drainage of the thyroid?
Superior and middle thyroid veins (drain into internal jugular vein)
Inferior thyroid veins (drain into innominate and brachiocephalic veins)
The recurrent laryngeal nerve innervates all of the muscles of the larynx except this muscle?
Cricothyroid muscle, which is innervated by the external branch of the superior laryngeal nerve
What structures do the recurrent laryngeal nerves wrap around?
Subclavian artery on the right
Arch of the aorta on the left
Injury to which nerve results in loss of projection and voice fatigability?
Superior laryngeal nerve
What is the mechanism of action of propylthiouracil (PTU) and methimazole?
Both drugs block peroxidase oxidation of iodide to iodine, thereby inhibiting
incorporation of iodine into T4 and T3
PTU also inhibits peripheral conversion of T4 to T3
Which drug crosses the placenta: PTU or methimazole?
PTU is the safer choice in pregnancy
When steroids are given in severe or acute hyperthyroid conditions? How do they work?
Steroids inhibit peripheral conversion of T4 to T3 and lower serum TSH by suppressing the pituitary-thyroid axis
What is the Wolff-Chaikoff effect?
Large doses of iodine given after an antithyroid medication can inhibit thyroid hormone
release by disrupting the coupling of iodide
This is a transient effect
HYPERTHYROIDISM/HYPOTHYROIDISM, AND GOITERS
What is the most common cause of hyperthyroidism?
Graves disease, also known as diffuse toxic goiter, is the cause of 60% to 80% of hyperthyroidism
What is the etiology of Graves disease?
Autoantibodies to TSH receptors (also called thyroid-stimulating antibodies or TSAb)
bind and stimulate thyroid hormone production
This leads to thyrotoxicosis, diffuse goiter, pretibial myxedema, ophthalmopathy
A 55-year-old woman presents with a 3-year history of fatigue and mild, diffuse, nontender thyroid enlargement and 15-lb weight loss. What is the most likely diagnosis?
What is the most common cause of hypothyroidism in adults?
What is the first-line treatment for Hashimoto thyroiditis?
Thyroid hormone replacement
What will pathology show in a patient with Hashimoto thyroiditis?
A 35-year-old female presents with sudden onset of severe pain and associated swelling and tenderness of her thyroid with fever, chills, and dysphagia following an acute upper respiratory infection. What is the most likely diagnosis?
Acute suppurative thyroiditis
What is the treatment for acute suppurative thyroiditis?
Occasionally, abscess drainage
A 35-year-old female presents with moderate swelling and tenderness of her thyroid with repeated exacerbations and remissions over several months following an acute upper respiratory infection. What is the most likely diagnosis?
Subacute (de Quervain) thyroiditis
What is the treatment for subacute (de Quervain) thyroiditis?
A 40-year-old female presents with hypothyroidism and symptoms of tracheal and esophageal compression and is found to have dense fibrosis throughout her thyroid gland. What is the most likely diagnosis?
Riedel fibrous struma
Painless, progressive goiter
Usually euthyroid may become hypothyroid
What is the treatment for Riedel fibrous struma?
Thyroid hormone replacement and steroids
Surgery may be necessary to relieve obstructive symptoms
What is the treatment of thyroid storm?
PTU or methimazole q4 to 6 hours and inorganic iodide to block synthesis and release of
Dexamethasone to inhibit peripheral conversion of T4 to T3
What are indications for surgery with a multinodular goiter?
Inability to rule out cancer
FIGURE 12-2. Management of a solitary thyroid nodule. a, except in patients with a history of external radiation exposure or a family history of thyroid cancer; FNAB, fine-needle aspiration biopsy; RAI, radioactive iodine; T4, thyroxine. (Reproduced from Brunicardi FC, Andersen DK, Billiar TR, et al. Schwartz’s Principles of Surgery. 9th ed. www.accessmedicine.com. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.)
What is the diagnostic test of choice for the evaluation of a thyroid nodule?
It has a sensitivity of 86% and specificity of 91%
Initial cytology is nondiagnostic in 20% to 25% of cases
However, a diagnosis of malignancy in FNA is highly accurate, approaching 100%
Medullary thyroid carcinoma (MTC)
What are the cytologic features of MTC?
Amyloid among neoplastic cells
Immunohistochemistry positive for calcitonin
Positive staining for carcinoembryonic antigen (CEA) or calcitonin gene-related peptide
Heterogeneity with polygonal or spindle-shaped cells
What percentage of MTC is sporadic?
75% to 80%
Unable to differentiate familial versus sporadic at presentation—all should be tested for rearranged during transfection (RET) mutation, pheochromocytoma, and
What operation should be done for MTC?
High incidence of multicentric disease
By what age should MEN 2a and MEN 2b patients undergo total thyroidectomy?
MEN 2a—age 6
MEN 2b—age 1 to 2
How can you follow patients after thyroidectomy for MTC?
History and physical examination
What are the cytologic features indicative of anaplastic thyroid carcinoma?
Grossly firm and white
Marked heterogeneity with spindle, polygonal, or multinucleated cells
What is the prognosis for anaplastic thyroid carcinoma?
Poor—only few survive more than 6 months
Who typically gets anaplastic thyroid carcinoma?
Elderly patients with a long-standing goiter
What is the treatment for a small anaplastic thyroid carcinoma?
Total thyroidectomy with or without external beam radiation
Has small improvement in survival, especially for younger patients
What is the treatment for anaplastic thyroid carcinoma with compressive symptoms?
Debulking surgery with tracheostomy
Which patient has a higher likelihood of malignancy: the patient with a solid thyroid lesion versus cystic thyroid lesion?
Solid thyroid lesion
Which patient has a higher likelihood of malignancy: the patient with a solitary thyroid lesion versus multiple thyroid lesions?
Solitary thyroid lesion
Which patient has a higher likelihood of malignancy: the patient with a hot thyroid lesion versus cold thyroid lesion?
Cold thyroid lesion
Papillary thyroid cancer, about 70% to 80% of all thyroid cancers
Which subtypes carry a worse prognosis?
What are the histologic findings for papillary thyroid carcinoma?
Orphan Annie nuclei
What is the treatment for papillary thyroid carcinoma?
High-risk, large (>2 cm), or bilateral tumors—total thyroidectomy
Low-risk, small (<1 cm), or unilateral tumors—thyroid lobectomy and isthmusectomy
What laboratory test is followed after surgery to monitor recurrence?
True or False: Positive cervical nodes affect the prognosis of papillary thyroid carcinoma?
False; positive cervical nodes do not affect the prognosis of papillary thyroid carcinoma as long as disease is resectable.
What are the histologic findings needed to define malignancy in follicular cancer?
Blood vessel, capsular invasion
What is the most common site of distant metastasis for follicular thyroid carcinoma?
Next most common is lung
Spread is hematogenous
Which has a worse prognosis: Hurthle cell carcinoma or Follicular carcinoma?
Hurthle cell carcinoma
Higher recurrence rate usually to regional lymph nodes
Name the 3 classifications systems specific to papillary thyroid cancer:
AGES (age, grade of tumor, extent of tumor, size)
AMES (age, metastasis, extent of tumor, size)
MACIS (metastasis, age, completeness of resection, local invasion, size)
High-risk patients by AGES or AMES criteria: >40 years old, male, capsular invasion or extrathyroidal extension, regional or distant metastases, size >4 cm, or poorly differentiated carcinoma
What is the (tumor, node, metastasis) (TNM) stage for a 57-year-old patient who underwent a total thyroidectomy for a 2.5-cm mass that was determined to be papillary thyroid carcinoma? All lymph nodes were free of disease and there was no extrathyroidal disease.
This patient has T2N0M0 disease
Because the patient is older than 45 years, this is stage II papillary thyroid cancer See Table 12-1
What are the indications for I-131 therapy?
All stage III or IV disease
All stage II disease younger than 45 years old
Most patients 45 years or older with stage II disease
Stage I disease who have aggressive histologies, nodal metastases, multifocal disease, and extrathyroid or vascular invasion
PARATHYROID EMBRYOLOGY, ANATOMY, AND PHYSIOLOGY
What structure are the superior parathyroid glands embryologically derived from?
Fourth branchial pouch
What structure are the inferior parathyroid glands embryologically derived from?
Third branchial pouch
What structure is the thymus embryologically derived from?
Third branchial pouch
What is the arterial blood supply to the superior parathyroid glands?
Inferior thyroid artery (occasionally by branches of the superior thyroid artery)
What is the arterial blood supply to the inferior parathyroid glands?
Inferior thyroid artery
What is the spatial relationship of the inferior parathyroid gland to the recurrent laryngeal nerve and inferior thyroid artery?
Inferior parathyroid glands are medial to the recurrent laryngeal nerves and located below the inferior thyroid artery
What is the spatial relationship of the superior parathyroid gland to the recurrent laryngeal nerve and inferior thyroid artery?
Superior parathyroid glands are lateral to the recurrent laryngeal nerves and located above the inferior thyroid artery
FIGURE 12-3. Relationship of the parathyroids to the recurrent laryngeal nerve. a., artery; v., vein. (Reproduced from Brunicardi FC, Andersen DK, Billiar TR, et al. Schwartz’s Principles of Surgery. 9th ed. www.accessmedicine.com. Copyright © The McGraw-Hill Companies, Inc. All rights reserved.)
Describe the mechanisms by which PTH increases serum calcium concentration:
Bone—enhances resorption of bone matrix by osteoclasts
Kidney—increases tubular reabsorption of filtered calcium and decreases tubular reabsorption of filtered phosphate
Intestine—stimulates renal vitamin D complex synthesis, which increases intestinal absorption of calcium (indirect effect)
What laboratory test is the most sensitive and specific way to diagnose hyperparathyroidism?
Intact parathyroid hormone level (elevated in >95% of patients with primary hyperparathyroidism)
What is the half-life of parathyroid hormone?
2 to 4 minutes
What is the desired decline in the intraoperative parathyroid hormone assay that confirms that the suspected abnormal parathyroid tissue was resected?
50% decrease from baseline PTH or a drop of the PTH to the normal range