The thyroid gland has important roles in metabolism, growth, and development. It is supplied by the superior and inferior thyroid arteries and drains into the internal jugular and innominate veins. The recurrent laryngeal nerve is at risk during surgery due to its close proximity. Hyperthyroidism has many potential causes like Graves' disease and toxic multinodular goiter. Treatment depends on the etiology and may include antithyroid medications, radioactive iodine, or surgery. Hypothyroidism is often autoimmune like Hashimoto's thyroiditis but can also be caused by infection, radiation, or fibrosis. Thyroid nodules and cancers are evaluated by FNA biopsy. Pap

1. Thyroid Review

2. Anatomy
Anatomy:
first and second pharyngeal arch
Blood supply
Superior thyroid artery- first branch of the external carotid artery
Inferior thyroid artery- off of thyrocervical trunk
Ima artery- in 1% of pop; goes straight to isthmus. From innominate or aorta
Ligate close to thyroid to preserve parathyroid
Venous drainage:
Superior and middle thyroid -> IJ
Inferior thyroid -> Innominate

3. Anatomy pt 2
Nerve:
Superior Laryngeal- CRICOTHYROID
Lateral to lobes
MC injured
Decrease projection/ easy fatiguability
Recurrent Laryngeal- MOTOR to all of larynx except cricothyroid
Left goes around aorta. Right goes around innominate
Hoarseness/ Airway compromise if bilateral
Right more injured than left
Ligament of berry- postero-medial suspensory ligament close to RLN
Tubercles of Zuckerkandle- most lateral/ posterior extension of thyroid tissue; left behind in subtotal

4. Physiology
Physiology:
Hypothalamus releases TRF  Anterior Pituitary  releases TSH  increase T3 and T4  negative feedback
Thyroid hormone: neural and somatic development; bone development; B-action in heart; bowel action;
metabolism
Peroxidase: link iodine and tyrosine
Deiodinase: separate the above
Thyroglobulin: stores T3/T4 in colloid (1:15 ratio)
Thyroxine binding globulin: hormone transport
C Cells: produces calcitonin
** Thyroxine- hormone replacement. Decreases TSH by 50% if working. SE: Osteoporosis
** Post-op stridor- if hematoma  emergent decompression
Also consider possibility of b/l RLN injury  need tracheostomy

5. Variations
Anatomic Variation
Pyramidal Lobe- 10%. Isthmus towards thymus
Lingual Thyroid- thyroid tissue in foramen cecum at the base of the tongue
Dysphagia, dyspnea, dysphonia
2% malignancy risk
Only thyroid tissue in 70% of pts
TX: Thyroxine suppression abolish w/ I-131  if doesn’t work: surgical resection
Thyroglossal Duct – midline lesion between hyoid and thyroid
Moves up with swallowing
Infection and malignancy risk
TX: resection; take midportion or all of hyoid

6. Hyperthyroidism
Hyperthyroidism
Thyroid storm- increase HR, numbness, irritability, vomiting, diarrhea, high output cardiac failure
Can be triggered by post op, anxiety, or adrenergic
TX: b-blocker; Lugol Solution (takes time to work; Wolf-Chaikoff Effect  decreases TSH, coupling, T3/T4)

7. General Management
General Management
Thioamides
Methimazole- 1st line. Inhibits peroxidase
Do not use in pregnant women
SE: cretinism, aplastic anemia, agranulocytosis
PTU- Safe in pregnancy
Hepatotoxic + above side effects
I-131 – not for children or pregnant women
Thyroidectomy- cold nodules, toxic adenomas, Graves, pregnant women (2nd trimester), multinodular

8. CausesGraves aka toxic diffuse goiter
MCC (80%)
F, exophthalmos, pretibial edema, A fib, heat intolerance, thirst, increased appetite, WL, palpitations, sweating
IgG antibodies to TSH Long Acting Thyroid Stimulator (LATS) Receptor; TSI
Decreased TSH; Increase T3/T4; Increase LATS
TSH: Medical therapy; Surgery if failed (give methimazole 1st, then b blocker, then lugol solution)
Toxic multinodular goiter
F, fifty, usually non toxic initially
Hyperplasia is 2/2 to chronic TSH stimulation
**colloid on pathology
I-131; surgery
Single toxic nodule
F, younger
Hot nodule on scan
TX: ThioamideI-131lobectomy
Rare: trophoblastic tumor, TSH secreting pituitary tumor

9. Hypothyroidism
Hashimoto- MCC. Enlarged, painless, chronic
F, history of XRT
Can initially present as thyrotoxicosis
Humoral and cell mediated autoimmune mediated  microsomal and thyroglobulin antibodies
TX: thyroxine; partial thyroidectomy
Bacterial- contiguous spread (URIs)
Get TFTs
TX: ABX +/- lobectomy
De Quarvains- viral URI. Tender thyroid, sore throat, weakness, fatigue
Increased ESR
TX: Steroid, ASA +/- lobectomy
Reidel’s Fibrous Struma
Woody, fibrous. Can involve straps
PSC, Fibrotic diseases
** need to biopsy
TX: steroids, thyroxine +/- tracheostomy for airway

10. Thyroid Lesions
Thyroid Nodules- 90% benign
FNA  best initial test
General Findings:
Follicular- lobectomy
Thyroid CA- lobectomy vs thyroidectomy
Colloid- low malignant potential
Cyst Fluid- drain; if recurs OR bloody  lobectomy
Normal Tissue- likely solitary toxic nodule
Medical management
If indeterminantradionuclide study
Hot- med management +/- surgery
Cold- lobectomy
Goiter- med +/- surgery

11. Thyroid CancerMC endocrine malignancy
Solid, solitary, cold, slow growth, hard, male, >50, XRT, MEN IIa/b
Papillary Thyroid Carcinoma- MC thyroid CA (85%)
Least aggressive
RF: XRT
Lymphatic spread 1st; prognosis is based on LOCAL INVASION. Rarely mets
**PSAMMOMMA BODIES; ORPHAN ANNIE EYES
95% 5yr survival
Follicular Thyroid Carcinoma
If follicular cells on FNA 5-10% chance of malignancy (but cannot differentiate between adenoma,
hyperplasia, or cancer)
Cancer has hematogenous spread (to bone)
70% 5yr survival
For papillary and follicular thyroid carcinoma:
Lobectomy  if >1cm, extra thyroidal, multi centric, b/l, prior XRT = total
**if extrathyroidal, >1cm, lymph nodes  MRND + I-131

12. Thyroid Cancer 2
Medullary Thyroid Cancer
Can be associated with MEN IIa/b; Parafollicular C Cells- calcitonin  can cause flushing and/or diarrhea. 50%
5yr survival
Diarrhea is typically 1st manifestation
C Cell hyperplasia = premalignant
**Amyloid on pathology
TX: total thyroidectomy + central node dissection +/- MRND (if palp mass. b/l if extrathyroidal)
PROPHYLACTIC IIa @ 6yo; IIb @ 2yo
Lymphatic Spread; early mets to the lung, liver, bone
Anaplastic
Elderly, long standing goiter
Most aggressive
Palliative
Hurthle Cell- 80% benign
Ashkenazi cells
Need lobectomy  total if malignant +/- MRND (if + node)

13. Further treatment considerations
I-131 is only for papillary or follicular cancer. 4-6 weeks after surgery
XRT- for all except anaplastic
Thyroxine- after I-131