Multinodular goiter

Multinodular goitre (MNG)is defined as an enlarged thyroid gland (i.e. goitre) due to multiple nodules which may have normal, decreased or increased function. 

Terminology

When increased activity and hyperthyroidism are present then the condition is referred to as a toxic multinodular goitre or Plummer disease. 

Multinodular goitre has been criticised as being a somewhat unhelpful term as some multinodular thyroids are not enlarged, resulting in the unwieldy term "multinodular non-enlarged thyroid" ⁷.

Clinical presentation

Multinodular goitre is seen more commonly in females (M:F=1:3) in the 35-50 years age range, who present with nodular enlargement in the midline of the neck. Patients are usually euthyroid, but the nodules may also be hypo- or hyperfunctioning, resulting in systemic symptoms from hypothyroidism or hyperthyroidism, respectively.

Pathology

Multinodular goitres develop from simple goitres as a result of repeated instances of stimulation and involution ⁴. 

Most of the nodules are hyperplastic or adenomatous with varying degree of cystic/liquefactive degeneration. Presence of serous/colloid fluid may be noted.

A nodule in multinodular goitre may harbour malignancy. A family history of malignancy and prior neck radiation exposure are known risk factors ².

Radiographic features

Ultrasound

Sonography remains the first radiological investigation to screen the nodules and look for any suspicion of malignant change in the nodules which is not uncommon.

Usually, the benign nodules in a multinodular goitre show the following features:

• iso-hyperechoic
• surrounding hypoechoic halo
• spongiform/honeycomb pattern
  • anechoic areas may contain colloid fluid which may show echogenic foci with comet tail artifacts
  • see: colloid nodule
• peripheral (eggshell) or coarse calcifications
• Doppler: peripheral vessels are usually noted, may show intranodular vascularity (mostly in hyperfunctioning nodules)

It is important to screen for the presence of malignant features (if any) in any of the nodules and subsequent FNA can be done from the suspicious nodule.

Malignant sonographic features

• hypoechoic solid
• intranodular blood flow
• large size: the cut-off is often taken as 10 mm to warrant an FNA
• presence of microcalcifications: almost always warrants an FNA

Benign sonographic features

• large cystic component
• hyperechoic solid
• comet tail artifact
• halo

See main article assessment of thyroid lesions for further details. 

Nuclear medicine

• Tc-99m pertechnetate or radioiodine (I-123) demonstrate an enlarged gland, with heterogeneous uptake
• thyroid uptake scan determines the activity of the gland
  • a toxic multinodular goitre will show high uptake within the nodules on a background of reduced uptake within the thyroid (cold thyroid)
  • a non-toxic multinodular goitre will show mild nodular uptake on a background of normal thyroid uptake

Plain radiograph

• goitre is in the differential for an anterior/superior mediastinal mass and is associated with the cervicothoracic sign
• associated with deviation of the trachea

CT

• not a primary modality for diagnosis, but may be seen incidentally
• CT may be useful for fully characterising the extent of substernal (retrosternal) goitre
• an enlarged and heterogeneous thyroid gland suggests the diagnosis, which is confirmed by ultrasound or scintigraphy

Treatment and prognosis

Treatment of multinodular goitre may be pursued if the thyroid is hyperfunctioning, or if the goitre is causing local mass effect. There is no standard treatment and choice of treatment depends on local practice patterns, the activity of the goitre, and the results of FNA of any suspicious nodules.

• surgery: partial or complete resection
• radioiodine: occasionally used 
  • dose  =  (thyroid weight x planned radioiodine delivery to thyroid) / radioiodine uptake
  • hypothyroidism may occur as an adverse event

Conservative management is also an option as some goitres decrease their rate of growth or may even decrease in size ⁶.

Practical points

• patients with multinodular goitre are at increased risk of iodinated contrast-induced thyrotoxicosis (although this is rare in itself) ⁵