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

DRUGS

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?

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

Antithyroid medication

Thyroid ablation

With/without thyroidectomy

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?

Hashimoto thyroiditis

What is the most common cause of hypothyroidism in adults?

Hashimoto thyroiditis

What is the first-line treatment for Hashimoto thyroiditis?

Thyroid hormone replacement

What will pathology show in a patient with Hashimoto thyroiditis?

Lymphocytic infiltrate

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?

Antibiotics

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?

NSAIDs, steroids

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

thyroid hormones

Dexamethasone to inhibit peripheral conversion of T4 to T3

Propanolol

Fever reduction

General resuscitation

Multinodular goiter

What are indications for surgery with a multinodular goiter?

Inability to rule out cancer

Compressive symptoms

Cosmetic deformity

CANCER

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
hyperparathyroidism

What operation should be done for MTC?

Total thyroidectomy

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?

Calcitonin levels

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?

Insular

Columnar

Tall cell

What are the histologic findings for papillary thyroid carcinoma?

Psammoma bodies

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?

Thyroglobulin

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?

Bone

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

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 GLAND

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