Parathyroid adenoma

Parathyroid adenomas are benign tumors of the parathyroid glands, and are the most common cause of primary hyperparathyroidism.

Patients present with primary hyperparathyroidism: elevated serum calcium levels and elevated serum parathyroid hormone levels. This results in multisystem effects including osteoporosis, renal calculi, constipation, peptic ulcers, mental changes, fatigue, and depression.

They are usually oval or bean-shaped, but larger adenomas can be multilobulated. The vast majority (up to 87% 2) of adenomas occur as solitary lesions.

The majority of parathyroid adenomas are juxtathyroid and located immediately posterior or inferior to the thyroid gland. Superior gland parathyroid adenomas may lie posteriorly in the tracheo-esophageal groove, paraesophageal location, or even as inferior as the mediastinum 12.

Up to 5% of parathyroid adenomas can occur in ectopic locations. Common ectopic locations include 1,12:

  • mediastinum
  • retropharyngeal
  • carotid sheath
  • intrathyroidal

Parathyroid hormone levels are usually elevated (usual normal reference range 1.6-6.9 pmol/L or 10 to 55 pg/mL).

Ultrasound is one of the most commonly used initial imaging modalities.

  • most nodules need to be >1 cm to be confidently seen on ultrasound
  • parathyroid adenomas tend to be homogeneously hypoechoic vs the overlying thyroid gland
  • an echogenic thyroid capsule separating the thyroid from the parathyroid may be seen

Can commonly show a characteristic extrathyroidal feeding vessel (typically a branch off the inferior thyroidal artery 1,6), which enters the parathyroid gland at one of the poles. Internal vascularity is also commonly seen in a peripheral distribution. This feeding artery tends to branch around the periphery of the gland before penetration. This feature can give a characteristic arc or rim of vascularity. The overlying thyroid gland may also show an area of asymmetric hypervascularity that may help to locate an underlying adenoma.

Can be very useful for localizing the lesion when the site is not known. Shows increased uptake with agents such as technetium (Tc) 99m Sestamibi (MIBI) (commonly used agent) and Tc-99m tetrofosmin. The nuclear medicine scan can be fused with the CT scan as a SPECT scan to increase diagnostic accuracy and aid in anatomical localization. 18F-fluorocholine PET/CT may also have a role 18.

In the past, CT was more commonly used in the setting of a failed parathyroidectomy for the detection of suspected ectopic glands (often mediastinal) 6.  However, in recent years, 4D-CT has emerged as valuable modality especially in the era of minimally-invasive parathyroidectomy. This type of surgery requires precise localization with anatomical detail and a confident diagnosis of parathyroid adenoma. 4DCT has been shown to be more sensitive than sonography and scintigraphy for preoperative localization of parathyroid adenomas 13,15.

On 4D-CT parathyroid adenomas typically demonstrate intense enhancement on arterial phase, washout of contrast on delayed phase and low attenuation on non-contrast imaging 12.

Secondary signs include 14:

  • the polar vessel which represents an enlarged feeding artery or draining vein to the hypervascular parathyroid adenoma
  • a larger lesion size increases the confidence of diagnosis
  • parathyroid adenomas can also show cystic change

MRI is infrequently utilized in initial work up because of lower spatial resolution and artifacts. Adenomas can show variable signal intensity on MRI. Reported signal characteristics include:

  • T1
    • typically intermediate to low signal
    • subacute hemorrhage can cause high signal intensity 6
    • fibrosis or old hemorrhage can cause low signal intensity 6
  • T2
    • typically hyperintense
    • subacute hemorrhage can cause high signal intensity 6
    • fibrosis or old hemorrhage can cause low signal intensity 6

Since most lesions demonstrate high T2 signal intensity, the addition of contrast for MRI does not significantly increase detection.

Surgery is successful in treating primary hyperparathyroidism caused by parathyroid adenomas in 95-98% of cases 17.

For a non-ectopic adenoma on ultrasound, consider:

Article information

rID: 23949
System: Head & Neck
Synonyms or Alternate Spellings:
  • Parathyroid adenomas
  • Parathyroid adenomata
  • Adenoma of parathyroid gland
  • Adenomas of parathyroid gland
  • Adenoma of parathyroid glands

Support Radiopaedia and see fewer ads

Cases and figures

  • Figure 1: gross pathology
    Drag here to reorder.
  • Case 1: on ultrasound
    Drag here to reorder.
  • Case 2: scintigraphy - ectopic adenoma
    Drag here to reorder.
  • Case 3
    Drag here to reorder.
  • Case 4
    Drag here to reorder.
  • Case 5
    Drag here to reorder.
  • Case 6: ectopic
    Drag here to reorder.
  • Case 7
    Drag here to reorder.
  • Case 8
    Drag here to reorder.
  • Case 9
    Drag here to reorder.
  • Case 10
    Drag here to reorder.
  • Case 11
    Drag here to reorder.
  • Case 12
    Drag here to reorder.
  • Case 13
    Drag here to reorder.
  • Case 14: MRI
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.