Goiter & Substernal Goiter

Cause for most goiter formation is unknown and not the fault of the patient.

• Exceptions include:
  • Endemic goiter which forms in iodine deficient regions of the world.
    • Iodine is essential for production of thyroid hormone.
      • Recommended daily dose is 150 mcg, ingestion of greater amounts may cause thyroid dysfunction.
      • It is very uncommon to be iodine deficient in developed countries.
    • When insufficient levels of iodine are available to the gland, the thyroid becomes less efficient at producing thyroid hormone and subsequently enlarges to compensate for this.
    • The Midwest of the United States was once considered a ‘goiter belt’ due to iodine deficient soil as the result of glacier effects during the Ice Age.
      • In the 1920’s, salt began to be iodinated in the US and the rate of endemic goiter in this region fell considerably.
  • Hereditary goiter which can run in families due to inherited genetics.
  • Secondary formation as the result of Graves’ Disease or Hashimoto’s thyroiditis.

• Discovered on routine physical exam.
• Incidentally on imaging of the neck or chest.
• During work-up of compressive symptoms (e.g. choking sensation,
  constant pressure low in the front of the neck, difficulty swallowing or breathing, etc.).

Depending on the size and location of a goiter, it can push on important structures in the neck causing compressive symptoms:

• Trachea / Windpipe.
  • This can result in symptoms of feeling choked, pressure low in the neck (which can be position dependent – looking down, turning your head sided to side, laying down in bed), shortness of breath at rest or with activity, stridor (loud / audible breathing during the day, particularly on the inhale).
• Pharynx / Esophagus.
  • Difficulty swallowing, particularly solid foods like meat and dry foods like bread.
• Typically, Goiters are slow growing, and the body accommodates well to small changes overtime, therefore sometimes goiters can get quite large before they become symptomatic.
  • This can be dependent on the relative size of the patient (smaller people may become symptomatic earlier) and location of the goiter (deeper goiters may become symptomatic earlier).
• Since goiters are solid structures and do not fluctuate in size on a day-to-day basis, true compressive symptoms are typically experienced daily, as opposed to occasionally.

Physical Exam

• Does palpation re-create or worsen subjective compressive symptoms?
• Can you feel the lower border of the goiter?
  • If not, the goiter may extend into the chest cavity (aka substernal goiter).

Labs

• Thyroid function labs (TSH and free T4) to rule out hyperthyroidism.
  • If hyperthyroidism is confirmed (low TSH and elevated free T4), a thyroid uptake scan should be performed to differentiate Graves’ goiter from a toxic hot nodule or toxic multinodular goiter.

Imaging

• Ultrasound of the thyroid is the preferred study for both initial and follow-up imaging.
• CT Scan of the Neck
  • Considered if there is suspicion for substernal goiter (cannot feel the lower border of the goiter or felt extending down to the level of the collar bone).
  • If the goiter is massive on exam or the compressive symptoms are significant.
    • CT Scan can give a much better 3-dimensional structural image to allow for a more complete evaluation and assist in surgical planning.

Ruling out cancer

• Risk in general for cancer is fairly low for diffusely enlarged goiters without thyroid nodules.
  • Consideration can be made to perform biopsy (FNA) without a distinct nodule to assure benign disease which may impact decision for surveillance or extent of surgery if elected.
• For a single nodule causing goiter or a multinodular goiter, each nodule should be independently assessed for risk of cancer (up to 4 nodules total).
  • Decision for FNA is based on Ultrasound appearance and size using TiRADS guidelines.
  • Generally, the more nodules that are present in a goiter, the relatively lower the risk for cancer.
  • Biopsy is usually not indicated in a thyroid gland that is replaced by multiple, confluent (touching) nodules of similar low to medium risk appearance.
    • This type of multinodular goiter has an extremely low risk for being cancer, so long as none of the nodules have high risk features.

Surgery to remove the affected lobe or entire gland should be considered if:

• There is steady significant objective growth on consecutive thyroid ultrasounds.
  • Especially in younger patients with many years for potential continued growth.
• Worsening compressive symptoms that effect the patient’s quality of life on a daily basis and can be confidently attributable to the goiter.
  • Based on exam – palpation recreating or making symptoms worse.
  • History – goiters are solid structures and do not fluctuate on a day-to-day basis, therefore true compressive symptoms are typically experienced daily, as opposed to occasionally.
• Cosmetic concerns.
  • Visible mass in the neck drawing unwanted attention.
• Surgery is to remove the entire thyroid lobe (Hemithyroidectomy) or both lobes (Total Thyroidectomy) being affected.
  • Individual nodules or groups of nodules should not be carved out of the thyroid in order to preserve thyroid function.
    • Attempting to carve nodules out in order to preserve thyroid function increases the risk for recurrence of the goiter in the future and risk of injury to nearby structures during the surgery, including the recurrent laryngeal nerve controlling voice and breathing.

Surveillance can be considered for patients that:

• Do not meet the above criteria for surgery.
• Patient preference to avoid surgery.
• Old age with low life expectancy.
• Patient is deemed an inappropriately high risk for anesthesia.
  • Co-morbidities (serious medical problems) causing increased risk for general anesthesia.
  • Increased risk for intra-operative or post-operative bleeding based on need for blood thinners or inherit blood clotting issues.
• Surveillance can be performed with yearly or almost yearly ultrasounds until 5 years of objective stability is established.
  • More frequent if change in exam or compressive symptoms develop / worsen.
  • Limitations of ultrasound measurements for large goiters.
    • Measurements can fluctuate between institutions and technicians obtaining images.
      • Sometimes by 1.0 cm or more in multiple dimensions for large goiters.
    • Therefore, the patient and surgeon should be careful in interpreting changes on reports from year-to-year, especially if there is no obvious difference in exam or subjective symptoms to correlate to measurement changes.
    • Often times the focus of the ultrasound should shift from the size of individual nodules to the overall size of the goiter (thyroid lobes) given the limitation of ultrasounds and differences in subjective interpretations that can occur.

American Thyroid Association (ATA) guidelines recommend against the use of thyroid hormone medication (e.g., levothyroxine or Synthroid) to suppress TSH levels with the goal of shrinking or preventing further growth of a goiter.

ATA guidelines also recommend against the use iodine supplements with the goal of shrinking or preventing further growth of a goiter unless iodine deficiency has been objectively discovered.

• In cases of documented iodine deficiency, a daily iodine 150 mcg supplement is recommended (higher doses should not be used).

No peer reviewed literature exists to suggest diet (other than to treat objectively identified iodine deficiency) has shown to shrink or prevent the growth of goiters.

No other supplements or prescription medications have been shown to shrink or prevent the growth of goiters.

Goiter that extends below the level of the collar bones and/or behind the sternum (chest plate).

Diagnosis:

• Commonly discovered incidentally on imaging of the neck or chest.
• During work-up of compressive symptoms (e.g. choking sensation, constant pressure low in the front of the neck, difficulty swallowing or breathing, etc.).
• When the bottom of the goiter cannot be felt on exam or feels like it is pressing up against the collar bone / sternum, a CT Neck should be obtained to rule out substernal extension.
• Consider CT Neck if the extent of compressive symptoms seems out of proportion to what is felt on exam or seen on ultrasound.
  • Sometimes the goiter you can feel on exam or see on ultrasound is just the tip of an iceberg for a larger / deeper goiter that can only be appreciated on CT scan.
• Ultrasound cannot see through bone (collar bone / sternum / ribs) therefore is not ideal for the initial diagnosis or surveillance of substernal goiters.

Treatment

• The preferred treatment for substernal goiter is surgery.
  • Once the goiter extends into the chest, the risk that it can affect the function of important structures such as the trachea (windpipe), lungs, and large blood vessels to and from the heart becomes much higher.
  • Once the goiter extends into the chest, the surgery to remove it becomes more complicated and risks significantly increase compared to a standard thyroidectomy surgery:
    • Risks of injuring nearby critical structures such as the recurrent laryngeal nerve (controlling voice and swallowing).
    • Risk of significant bleeding during / after surgery.
    • Size of the incision necessary to remove the goiter increases.
  • Sometimes the substernal goiter is so large that it requires the assistance of a Thoracic surgeon to either open the sternum (aka sternotomy, similar to open heart surgery) or make an incision through the ribs (thoracotomy or thoracoscopy) and deflate the lung to help push the goiter up from below.

Observation

• When to consider observing a substernal goiter instead of removing it with surgery:
  • If the substernal extension is very minimal.
  • Review of CT imaging dating back several years shows objective stability.
  • Old age with low life expectancy (less time for possible continued growth).
  • Co-morbidities (significant health problems) causing increased risk for general anesthesia.
  • Increased risk for intra-operative or post-operative bleeding based on need for blood thinners or inherit blood clotting issues.
• Surveillance can be performed yearly with imaging until 5 years of objective stability is established, then less frequently thereafter.
  • Imaging should be obtained earlier if change in exam or compressive symptoms develop / worsen.
  • Unfortunately, ultrasound cannot be used to monitor substernal goiters given its inability to see through bone.
  • Requires CT of the Neck which is more costly than ultrasound and does involve a small amount of radiation exposure.
    • If steady growth is noted on repeat CT scans, there should be a low threshold to consider surgery before the risks become too high.

Medical Management

• Similar to non-substernal goiters (as discussed above), there is no role for medical management.

For all types of thyroid surgery, surgical outcomes are the highest and complication rates are the lowest when surgery is performed by a high-volume surgeon (> 50 thyroidectomy surgeries per year).

To read more about Thyroid surgeries including what to expect, as well as details regarding recovery and risks:

• Hemithyroidectomy.
• Total Thyroidectomy.