Endocrine Review

Question 1

Blood Supply to Thyroid

Answer 1

Superior Thyroid Artery (first branch of external carotid artery)

Inferior Thyroid Artery (off thyrocervical trunk)

Ima (occurs in 1%, off innominate or aorta and supplies isthmus)

Question 2

Blood supply to Parathyroids

Answer 2

Inferior thyroid artery

Question 3

Venous drainage of thyroid

Answer 3

Superior thyroid vein - drain into IJ

Middle thyroid vein - drain into IJ

Inferior thyroid vein - drain into innominate vein

Question 4

Feedback loop for thyroid hormone production

Answer 4

Thyrotropin releasing factor from hypothalamus acts on anterior pituitary to release TSH

TSH acts on thyroid to release T3 and T4 (by increasing cAMP)

Question 5

What does recurrent laryngeal nerve supply

Answer 5

Motor to all larynx except cricothyroid muscle

Question 6

What does superior laryngeal nerve supply

Answer 6

Motor to cricothyroid muscle

Question 7

Anatomy of Recurrent laryngeal nerve

Answer 7

Runs posterior to thyroid lobe in tracheoesophageal grove

Left RLN loops around aorta

Right RLN loops around innominate artery

Question 8

Anatomy of superior laryngeal nerve

Answer 8

Tracks close to superior thyroid artery but is variable

Question 9

Injury to recurrent laryngeal nerve

Answer 9

Hoarsness

Bilateral -> airway obstruction (consider tracheostomy)

Question 10

Injury to superior laryngeal nerve

Answer 10

Loss of voice projection and voice fatigability (Opera Singers)

Question 11

Role of thyroglobulin

Answer 11

Stores T3 and T4 in colloid, (Plasma T4 ratio is 15x greater than T3)

T3 is active form

Question 12

T3 production in periphery

Answer 12

Conversion by deiodinases which separate iodine from tyrosine

Question 13

Thyroid Storm Symptoms and Presentation

Answer 13

Symptoms: tachycardia, fever, high output cardiac failure

Presentation: surgery in patient w/ undiagnosed Graves

Question 14

Thyroid Storm Treatment

Answer 14

Beta blockers
Lugol's solution (Potassium iodine) - to inhibit TSH action on thyroid
Cooling blankets
Oxygen 
Glucose

Question 15

Diffuse enlargement of thyroid without evidence of functional abnormality - treatment

Answer 15

Thyroxine

Subtotal vs total thyroidectomy if failure of medial management

Question 16

Midline cervical mass between hyoid bone and thyroid isthmus

Answer 16

Thyroglossal duct cyst - moves upward with swallowing, can be susceptible to infection, maybe be pre-malignant

Tx: resect with mid portion of hyoid bone (sistrunk procedure)

Question 17

Treatment for hyperthyroidism

Answer 17

Methimazole (causes cretinism in pregnancy) or
PTU (Safe in pregnancy)

Both inhibit peroxidase to prevent iodine-tyrosine coupling

Side effect: aplastic anemia, agranulocytosis

Question 18

Most common cause of hyperthyroidism

Answer 18

Graves - due to IgG to TSH receptor

Diagnosed by decreased TSH, increased T3, T4, increased/diffuse iodine uptake

Question 19

Treatment of Graves

Answer 19

Thioamides, radioactive iodine, or thyroidectomy

Pre-op must have methimazole until euthyroid, beta-blockers and lug’s solution for 2 weeks prior to decrease friability and vascularity

Question 20

Most common cause of hypothyroidism in adults

Answer 20

Hashimoto’s disease caused by humeral and cell-mediated autoimmune disease

pathology = lymphocytic infiltrate

Question 21

Treatment of graves

Answer 21

Thyroxine (first line)

Partial thyroidectomy if fails medical treatment

Question 22

Presentation of De Quervain’s

Answer 22

Viral URI –> tender thyroid, weakness, fatigue, increased ESR

Question 23

Riedel’s fibrous struma

Answer 23

Woody, fibrous component involving thyroid, strap muscles and carotid sheath, can cause compressive symptoms

Tx w/ steroids and thyroxine

Question 24

Risk factors for Papillary thyroid cancer

Answer 24

Childhood XRT

Question 25

Pathology of Papillary Thyroid Cancer

Answer 25

Psammoma bodies (calcium)
Orphan Annie Nuclei

Question 26

Spread of Papillary Thyroid Carcinoma

Answer 26

Lymphatic first
Local invasion is most prognostic

Rarely mets to lungs

Question 27

Risk factor for Follicular thyroid carcinoma

Answer 27

Older women

Question 28

Spread of Follicular thyroid carcinoma

Answer 28

Hematogenous spread (bone most common), 50% have metastatic disease at presentation

Question 29

Treatment for papillary and follicular thyroid cancer

Answer 29

Total thyroidectomy if >1cm, extra thyroidal disease, multi-centric or prior XRT

Do modified radical neck dissection for extra-thyroidal disease

Post op radiactive iodine if tumor >1cm or extra thyroidal disease

Question 30

Etiology of Medually Thyroid Carcinoma

Answer 30

Associated w/ MEN IIa or IIb (RET proto-oncogene) but 80% sporadic

Occurs in parafollicular C cells which secrete calcitonin

present w/ flushing and diarrhea

Question 31

Pathology of Medullary thyroid carcinoma

Answer 31

amyloid deposition

Question 32

Spread of medullary thyroid

Answer 32

Lymphatic spread (most have nodes at time of diagnosis)

early mets to lung, liver, bone

Question 33

Treatment of medullary thyroid cancer

Answer 33

Total thyroidectomy w/ central neck dissection

Question 34

When to do thyroidectomy in Men IIa vs IIb

Answer 34

IIa - 6 years

IIb - 2 years

Question 35

Pathology of Anaplastic Thyroid Cancer

Answer 35

Vesicular appearance of nuclei

Question 36

Treatment of anapestic thyroid cancer

Answer 36

Palliative thyroidectomy vs chemo-XRT for compressive symptoms

Question 37

Pathology of Hurtle cell carcinoma

Answer 37

Ashkenazi cells - you cannot determine benign vs malignant on biopsy alone, requires lobectomy

If malignant do total thyroidectomy

Question 38

Which subtypes of thyroid cancer is radioactive iodine effective for

Answer 38

Papillary and follicular thyroid cancer only

Indications are recurrent cancer, >1cm or extra thyroidal disease