Advances in Thyroid Management

Educational Objectives

The goal of this program is to improve the medical and surgical management of thyroid disorders. After hearing and assimilating this program, the clinician will be better able to:

1.   Identify the differential diagnosis of hyperthyroidism and hypothyroidism.

2.   Prescribe the appropriate medical treatments for disorders of the thyroid.

3.   Employ newer, less invasive techniques for outpatient thyroid surgery.

4.   Apply appropriate therapy to prevent hypocalcemia in patients undergoing thyroidectomy

5.   Apply nerve monitoring as an adjunct to visual inspection of the recurrent laryngeal nerve.

Faculty Disclosure

In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the plan­ning committee to disclose relevant financial relationships within the past 12 months that might create any personal con­flicts of interest. Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business or commercial interest. For this program, the following has been disclosed: Dr. Terris is the Director of Thyroid Courses for Johnson & Johnson. Drs. Vaughters and Randolph and the planning committee reported nothing to disclose.

Acknowledgements

Drs. Vaughters, Terris and Randolph were recorded at Minimally Invasive and Conventional Surgical Management of Thy­roid and Parathyroid Disorders, held October 9-10, 2009, in Augusta, GA, and presented by the Medical College of Geor­gia and University of Pisa. The Audio-Digest Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.

Medical Treatment of Hyperthyroid and Hypothyroid States

R. Bauer Vaughters, MD, Aiken Center for Clinical Research, Aiken, SC

Thyroid hormone replacement: most patients receiving thyroxine (T₄; tetraiodothyronine) via levothyroxine; body converts T₄ to T₃ (triiodothyronine); inadequate or altered metabolism of thyroid hormone often results in reverse T₃; branded levothyroxine (eg, Synthroid, Levothroid, Unithroid, Levoxyl) preferable to generic unless cost prob­lematic; T₃ most active thyroid hormone in body, although less abundant than T₄; some patients unable to convert T₄ to T₃; can use direct T₃ replacement with liothyronine (Cytomel); data on long-term outcomes with liothyronine weak; some patients benefit from combination levothyroxine and liothyronine

Euthyroid sick syndrome: seriously ill patient with low thyrotropin (TSH) level, low to normal free T₄, low total T₃; as patient’s acute illness subsides, thyroid hormone levels normalize; full work-up unnecessary in these patients; measure reverse T₃ level

Stability of hormone levels: keep hormone levels stable; do not treat secondary conditions such as overweight or anxiety with thyroid hormone replacement; must target normal hormone level and treat secondary conditions sepa­rately to avoid complications, including irregular heart rhythms and osteoporosis (high thyroid hormone) and heart failure and hyperlipidemia (low thyroid hormone)

Hypothyroidism: autoimmune thyroiditis (Hashimoto’s thyroiditis) most common cause; other causes include sur­gery, radioactive iodine, and external radiation; clinical presentations  —  fatigue, weight gain, lack of energy and interest, and edema; advise patients that full work-up necessary; differential diagnosis  —  adrenal insufficiency, vitamin D deficiency, anemia, electrolyte abnormalities, liver and kidney dysfunction, depression, stress, anxi­ety; patients often convinced such symptoms hypothyroid-induced

Desiccated animal thyroid: eg, Armour thyroid; speaker opposes use; doses inconsistent and may deliver excess T₃; frequently requested (believed to be “natural”; gives energy boost); backlog in production causing increasing concern among some patients

Hormone replacement dosage: clinicians may increase too quickly because TSH levels slow to decrease; check no earlier than third or fourth week (except in special cases); check free T₄ and T₃ levels in addition to TSH before increasing dose

Myxedema coma: severe hypothyroidism; treat aggressively and early with high dose of intravenous (IV) levothy­roxine; may use IV triiodothyronine, steroids, and hydration; look for and treat underlying causes

Hyperthyroidism: patients anxious and irritable; may be uncomfortable in or disturbance to front office environ­ment; bring them to quiet back room as early as possible; laboratory findings  —  low TSH, high free T₄, high to­tal T₃; initial treatment  —  b-blockers (eg, propranolol 10-40 mg every 6 hr); treatment options include antithyroid medications (eg, methimazole, propylthiouracil), radioiodine, and surgery

Antithyroid medications: »50% remission rate; if successful, treat for »1 yr, then attempt discontinuation (»50% have recurrence); follow-up  —  liver function studies; white blood cell (WBC) count; check complete blood cell (CBC) count if infection suspected

Radioiodine ablation: thyroid hormone levels initially increase, then decrease after 2 to 3 wk; in severely ill pa­tients, treat with antithyroid medications first, (stopping treatment 1-2 wk before ablation) or monitor carefully after ablation; ablation less efficacious in large goiters (»70% success rate); surgery more cost-effective than ab­lation in certain patients (eg, uninsured)

Surgery: improvements in last decade; high satisfaction rate among patients; reduces noncompliance

Key points: desiccated animal thyroid not recommended; watch for hypopituitarism in patients with hypothyroidism; do not replace hormone too quickly when treating for abnormal TSH level (monitor free T₄ or T₃ level if possible); low TSH in setting of critical illness may be euthyroid sick syndrome rather than hyperthyroidism; conditions mimicking hypothyroidism include vitamin D deficiency anemia, adrenal insufficiency, and depression; compli­ance is issue with some patients

Outpatient Thyroid and Parathyroid Surgery

David J. Terris, MD, Edward S. Porubsky Distinguished Professor and Chair, Department of Otolaryngology-Head and Neck Surgery, and Surgical Director, Thyroid Center, Medical College of Georgia, Augusta

Trends in hospital stays: preoperative admission for most surgical operations increasingly rare (eg, open-heart sur­gery patients admitted day of surgery); tonsillectomy and cholecystectomy routinely done on outpatient basis

Factors minimizing invasiveness: smaller incisions and decreased need to raise subplatysmal flaps; successful he­mostasis and reduction in use of drains; reduction in need for postoperative calcium monitoring; decreased risk for bilateral paralysis of recurrent laryngeal nerve

Surgical technique: make horizontal incision; cut down to strap muscles; separate strap muscles superiorly to top of thyroid cartilage and inferiorly to sternal notch (avoid buttonholing of skin); elevate planes; hemostasis achieved using advanced energy surgical technology (eg, Harmonic, SonoSurg, LigaSure)

Drains: used to avoid expanding hematoma; speaker no longer uses drains; studies show no advantage to using drains (do not affect risk for complications)

Hypocalcemia: in outpatient thyroidectomy patients, administer routine calcium supplementation; patient may be­come transiently hypoparathyroid, but not hypocalcemic; 1-g doses of eg, OsCal-D, over 3-wk taper (3 times per day during week 1, twice per day during week 2, once per day during week 3)

Bilateral vocal cord paralysis: risk minimized by use of nerve monitoring; monitoring facilitates intraoperative strategy modifications, as information gradually revealed about condition of initial lobe; speaker employs preoper­ative and immediate postoperative laryngeal endoscopy

Benefits of outpatient thyroid surgery: costs »$2500 less than inpatient surgery; patients frequently prefer to con­valesce at home; decreases exposure to nosocomial organisms; minimizes chance of iatrogenic complications

Speaker’s experience: >400 patients, predominantly women; 220 total or completion thyroidectomies; 198 lobecto­mies; little difference in pathology between inpatients and outpatients; »50% outpatients; complications (eg, tem­porary hypercalcemia) and readmission more common in inpatients than outpatients

Robotics: remote-access technique  —  patient’s arm raised over head; incision made through axilla; procedure done with semirigid scope and conventional laparoscopic instruments; procedure takes »3 hr per lobe in best surgical hands; bilateral axillary breast areolar approach  — pop-ular among Asian patients because of avoidance of neck scar; Chung robotic axillary technique  — transaxillary approach with small presternal port; thyroid approached be­tween sternal and clavicular heads of sternocleidomastoid muscle, posterior to strap muscle; gasless technique; re­traction important; working on top of jugular vein and carotid sheath; energy device (eg, Harmonic) used for entire procedure; incision relatively large; drain used; patient admitted; speaker does lobectomies only when benign pa­thology anticipated; nerve monitoring during entire procedure; no neck scar; speaker does not think procedure will have wide application in United States

Nerve Monitoring in Thyroid Surgery

Gregory W. Randolph, MD, Associate Professor of Otolaryngology Head and Neck Surgery, Harvard Medical School, and Director, Division of Thyroid Surgery, Massachusetts Eye and Ear Infirmary, Boston, MA

Recurrent laryngeal nerve (RLN) anatomy: distal courses of left and right RLN run posterior to (or penetrate) lig­ament of Berry; RLN then leaves surgical field and enters larynx under inferior constrictor; RLN divides into ante­rior and posterior branches behind cricothyroid joint; RLN then joins descending fibers of internal branch of superior laryngeal nerve; in its paratracheal course, right RLN travels from lateral to medial as it ascends neck; right RLN situated at greater depth than left RLN in paratracheal region

Nerve monitoring: utility of nerve monitoring evident after 4 mo of empiric use in high-volume setting; source of added information not available through visualization; not meant to supplant knowledge of anatomy; during sur­gery, nerve revealed in increments; nerve monitoring allows nerve identification at earlier stage of procedure; as neither trachea nor blood vessels running parallel to nerve conduct electricity, signature electrical response con­firms location of nerve

Case: thin woman, normal thyroid gland; minimal visual information in surgical field; RLN small and thin; some band-like sections of fascia and vessels appear similar to nerve; nerve stimulation allowed differentiation be­tween structures

Distinguishing nerve branches: after finding nerve, stimulation can help distinguish between motor and sensory fi­bers

Preventing stretch injury: in ventral delivery, even minimal or judicious retraction of nerve (particularly at ligament of Berry) can cause damage due to stretching; nerve stimulation allows intraoperative monitoring of nerve func­tion (ie, ability to conduct electricity); posterior leaflet of ligament of Berry that entraps nerve can be very thin piece of tissue; usually revealed as “hooking up” of nerve with retraction of lobe; note contour of nerve; if nerve “hiking up” onto trachea (especially with acute angulation of nerve), lyse interfering fascia or vessel

Research data: studies of RLN paralysis with and without nerve monitoring suffer from insufficient power; unrealis­tic numbers of cases required to empirically prove advantages of nerve monitoring; base decision to use monitoring on observations of benefit

Monitoring rates in US: »40% of thyroid surgeries in US employ nerve monitoring; gap between use by otolaryn­gologists and general surgeons has closed; monitoring most common among younger surgeons and surgeons doing greater volume (>100 cases per year) of procedures

Myths about nerve monitoring: monitoring does not replace surgical skill or knowledge of anatomy; adds new functional dynamic; does not replace need to visualize nerve; does require bloodless field; may increase costs, but value outweighs additional cost

Basics: laryngeal exam essential both preoperatively and postoperatively; nerve stimulation response very sensitive (no electromyography [EMG] activity with stimulation 1 mm from nerve; stimulation on nerve creates deformation of baseline on EMG); waveform responses of endotracheal electrode and of hook wire (surface) electrode correlate well (ie, non-invasive surface stimulation effective for measuring EMG activity); activity begins aat »0.4 mA; maximum EMG activity at »0.8 mA; recommended stimulation level 2.0 mA to locate nerve, 1.0 mA to monitor nerve; repeated stimulations at 1 to 2 mA will not injure nerve

Benefit categories of nerve monitoring: aid in nerve identification; aid in dissection (particularly with repeat sur­geries); prognostication of postoperative nerve functioning

Prognosis: complete thyroidectomy puts both RLN branches at risk; estimated that only 1 of 10 injured nerves ac­curately identified by surgeon with visual inspection alone; after lobectomy, nerve stimulation at vagus gives negative predictive value of 99.6%; rate of paralysis extremely low if EMG signal strong at beginning of surgery and at end of lobectomy; when EMG signal strong before surgery but poor after lobectomy, 75% chance of paral­ysis; predictive value increases as user’s ability to troubleshoot monitoring system increases; stimulation also ca­pable of identifying specific location of injury along nerve

Assistance to nonspecialists: 90% of thyroid operations done by surgeons not specifically focusing on thyroid sur­gery (Udelsman analysis); 50% of thyroid surgeries in United States done by surgeons doing <5 per year (Michigan group)

When to use nerve monitoring: some cases clearly difficult and will benefit from nerve monitoring; difficulty of other cases may not present immediately

Superior laryngeal nerve (SLN): because of differential latency, EMG waveform allows differentiation between va­gus and aural sections

Additional applications: thyroid surgery incision  —  never too small for insertion of nerve monitoring device; be­cause less invasive approaches may entail smaller visual field, added electrical information more valuable; record­ing nerve stimulation  —  waveform and latency data can be recorded after surgery and sent along with dissected lobes to confirm postoperative functioning of nerve; now standard practice in Germany

Suggested Reading

Abboud B et al: Is therapy with calcium and vitamin D and parathyroid autotransplantation useful in total thyroidectomy for preventing hypocalcemia? Head Neck 30:1148, 2008; Barczynski M et al: Randomized clinical trial of visualization versus neuromonitoring of recurrent laryngeal nerves during thyroidectomy. Br J Surg 96:240, 2009; Hopkins B, Steward D: Outpatient thyroid surgery and the advances making it possible. Curr Opin Otolaryngol Head Neck Surg 17:95, 2009; Hydman J et al: Diagnosis and prognosis of iatrogenic injury of the recurrent laryngeal nerve. Ann Otol Rhinol Laryngol 118:506, 2009; In H et al: Treatment options for Graves disease: a cost-effective analysis. J Am Coll Surg 209:170, 2009; Johnson S, Goldenberg D: Intraoperative monitoring of the recurrent laryngeal nerve during revision thyroid surgery. Oto­laryngol Clin North Am 41:1147, 2008; Jonklaas J: Gender and age differences in levothyroxine dose requirement. Endocr Pract Oct 15, 2009 [Epub ahead of print]; Jumaily JS et al: Prediction of hypocalcemia after using 1- to 6-hour postopera­tive parathyroid hormone and calcium levels: An analysis of pooled individual patient data from 3 observational studies. Head Neck Sep 24, 2009 [Epub ahead of print]; Kang SW et al: Robotic thyroid surgery using a gasless, transaxillary ap­proach and the Da Vinci S system: The operative outcomes of 338 consecutive patients. Surgery 146:1048, 2009; Kennedy SA et al: Meta-analysis: prophylactic drainage and bleeding complications in thyroid surgery. J Otolaryngol Head Neck Surg 37:768, 2008; Nygaard B et al: Effect of combination therapy with thyroxine (T4) AND 3,5,3’-triiodothyronine ver­sus T4 monotherapy in patients with hypothyroidism, a double blind, randomized cross-over study. Eur J Endocrinol 161:895, 2009; Stoll SJ et al: Thyroid hormone replacement after thyroid lobectomy. Surgery 146:554, 2009; White WM et al: Recurrent laryngeal nerve monitoring during thyroidectomy and related cervical procedures in the pediatric popula­tion. Arch Otolaryngol Head Neck Surg 135:88, 2009.